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1986     Front Cover (1986)    No author information available Summary: Not available         Table of Contents (1986)    No author information available Summary: Not available         Conference Information (1986)    No author information available Summary: Not available         ACS-86 Editorial (1986)    J. Schooley Summary: Not available         H. Kamerlingh Onnes symposium on the origins of applied superconductivity 75th anniversary of the discovery of superconductivity (Insert)    No author information available Summary: Not available         H. Kamerlingh Onnes symposium on the origins of applied superconductivity 75th anniversary of the discovery of superconductivity    B. Deaver Jr. Summary: Not available         Superconductivity: Discoveries during the early years of low temperature research at Leiden 1908-1914    R. de Bruyn Ouboter Summary: Not available         Early superconductivity research (except Leiden)    A. Pippard Summary: Experiments and theories in the period between Meissner and Ochsenfeld (1933) and Bardeen, Cooper and Schrieffer (1957) are reviewed, with special emphasis on the development of phenomenological models of superconductivity.         Origins of the theory of superconductivity    L. Cooper Summary: A personal account is given of the events that led to the theory of superconductivity.         Superconducting tunneling spectroscopy and the observation of the Josephson effect    J. Rowell Summary: The discoveries associated with superconducting tunneling spectroscopy, its development with W. L. McMillan as a tool to measure the electron-phonon interaction in superconductors, and the first observation of the Josephson effect are described from a personal point of view.         Niobium superconducting magnets    G. Yntema Summary: The process of design and construction, in 1954, of the first superconducting magnet is described. That magnet had Nb windings on an Fe core. It produced .71T in a small gap at 4.2K. Other Nb magnets, both with and without Fe, were built at several laboratories. Some of them are described, along with the applications to which a few were put. Empirically, it was clear in the 1950s that the performance of Nb as magnet wire was spectacularly improved by cold work.         Recollection of events associated with the discovery of high field-high current superconductivity    J. Kunzler Summary: In this article, an attempt is made by the author to recall some of the more important events that led to the discovery of high field-high current superconductivity. After a little background, events are recalled from a few years before, until shortly after the discovery. Considerable attention is given to people events, thus emphasizing the human side of the period, as recalled by the author.         Type II superconductivity: Quest for understanding    T. Berlincourt Summary: By 1941, many of the essential experimental features of type II superconductivity had already been observed (de Haas and Voogd, Shubnikov et al., Keesom and Desirant). Moreover, truly remarkable progress had been made toward theoretical understanding based on negative interphase surface energy considerations (Gorter, H. London). However, a competing explanation, the filamentary sponge model, was proposed (Mendelssohn) in all attempt to explain magnetic hysteresis effects which tended to obscure the intrinsic thermodynamic character of type II superconductivity. This filamentary sponge model is now known to be of only very restricted applicability, but for more than two decades it enjoyed wide acceptance, so much so, that when the ultimate theoretical basis for type II superconductivity was formulated in the 1950's (Ginzburg and Landau, Abrikosov, Gorkov (GLAG)), it was largely ignored. With the discovery of the practical supermagnet potential of type II superconductors (Yntema, Kunzler et al.), interest in achieving deeper understanding of-high-magnetic-field superconductivity was reawakened. Only then was the power of the GLAG formalism very belatedly recognized, both with respect to near-ideal type II superconductors (Goodman) and with respect to non-ideal materials of technical interest (Berlincourt and Hake). Rapid experimental and theoretical progress followed on a number of significant aspects, including flux trapping, flux creep, and flux flow (Yntema, Anderson, Kim, Hempstead, Strnad), and surface superconductivity (Saint-James and de Gennes). Indirect "observation" of Abrikosov's vortex lattice was soon accomplished by neutron scattering techniques (Cribier et al.) and by nuclear magnetic resonance techniques (Pincus et al.). Finally, a more direct magnetic decoration technique (Essmann and Trouble) yielded remarkably graphic and incontrovertible pictoral confirmation of the Abrikosov vortex lattice.         The argonne bubble chamber supermagnet    J. Purcell Summary: The winding of the 12 ft. bubble chamber magnet is 16 ft. in diameter, 10 ft. tall, and weighs 50 tons. The magnet cryostat weighs another 50 tons and the iron return path has a weight of 1600 tons. It produces a field of 1.8 tesla and was first tested in December of 1968. After working for more than ten years at Argonne it was moved to the Stanford Linear Accelerator (SLAC) and became a part of the detector for a colliding electron beam experiment.         The past and the future of international collaboration in applied superconductivity - A European point of view    G. Brianti Summary: International collaboration has a very long tradidtion in fundamental research it is first of all promoted by the natural spreading of knowledge through scientific publications and, more recently by the need of grouping very substantial efforts (both financial and human0 around large ecperiements lasting several years.         Japanese international cooperation in superconductive technology    K. Oshima Summary: International cooperation has been one of the most predominant characteristics in the development of cryogenic engineering and, above all, superconductive technology in Japan. In factl the Cryogenic Association of Japan, which just celecbrated its 20th anniversary this year, was established primarily to host the First Internation Cryogenic Engineering Conference, ICEC-1, held in 1967 at Kyoto.         International cooperative--collaborative perspectives - Superconductive science and technology    J. Hulm and C. Laverick Summary: This paper discusses the achievements of Applied Superconductivity over the past 25 years and a brief outline of the present technical and commercial status of the field. Special attention is paid to the role of International collaboration and cooperation in superconducting research. The main topics covered include applications of superconductivity to Energy Technology, Particle Physics, Medical Equipment and Electronics. Natural resource limitations are discussed and some future application areas are suggested.         Collaborative superconductivity research in Europe    P. Komarek Summary: The collaboration in Europe for research in superconductivity, especially for large Scale applications, has a long tradition. In the early seventies already a so-called "GESSS group" (Group on European Superconducting System Studies) became active for accelerator and detector magnet development. In the second half of the seventies the fusion technology programme in Europe called for an increasing effort in magnet development. Due to the fact that the fusion work is at all a collaborative European effort and the earlier GESSS laboratories got involved in that area too, these activities were carried out jointly from the beginning. Participation in the IEA-Large Coil Task by two European groups also proved the capability of an even broader international collaboration. Based on the different management schemes for the collaborations lessons have been learned and are discussed, which might be valuable for foreseeable large European projects such as NET (Next European Torus) and LHC (Large Hadron Collider) in the next decade. The role of industry as a collaboration partner in the different areas is discussed, too.         Opportunities for international collaboration in superconducting electronics    H. Hayakawa Summary: It is said that international collaborations in superconducting electronics have become particularly important to share research risks and resources. The present status of technologies, recent cooperative research activities, and some comments on future cooperations in superconducting electronics are described.         Superconducting materials--An international challenge    T. Geballe Summary: Sevem decades ago the talk I'd have been asked to five on Superconducting Materials from the point of view of international collaborations would have veen simple. "Materials" then meant Sn. Hg, Pb, and their alloys, and "international" would have meant consulting the boat and train time tables to Holland. Today, with the exponentially inceasing capapilities of the tools of materials science, and concomittently their expense, international collaborations are not only an attractive way to proced, but maybe the only way to go.         Cosmic-ray monopole search at IBM-BNL using superconducting induction detectors    S. Bermon Summary: Supermassive magnetic monopoles are an inevitable consequence of all Grand Unified Theories (GUT's). They would have originated in the very hot early universe some 10/sup -35/sec. after the Big Bang when the unified force split apart into the strong and electroweak forces. Over thirty laboratories throughout the world have constructed or are presently constructing detectors to search for such primordial monopoles in cosmic rays. This paper, partly tutorial, reviews the past monopole detector work at IBM and describes the present effort to set-up at the Brookhaven National Laboratory a large-area superconducting induction detector. Two detectors are being built based upon the high-order gradiometer, fully coincident, closed-box design previously developed at IBM. The first, utilizing an existing magnet-testing dewar at BNL, is a rectangular parallelopiped detector of 1.0 m/sup 2/effective area (averaged over 4/spl pi/ sr for isotropie flux) being built to test the feasibility of large area schemes in preparation for construction of a much larger 4.0 m/sup 2/octagonal prism detector. The latter could serve as the prototype for an array of detectors to reach the Parker bound on monopole flux set by the existence of the 3 /spl mu/G galactic magnetic field in several years of operation.         Variation of the electrochemical potential difference in a gravitational field    A. Jain, J. Lukens and J.-S. Tsai Summary: We have determined the variation of the electrochemical potential difference in a gravitational field, and the results agree to within 4% with the predictions of the Equivalence Principle (EP). Thus, EP has again been verified, but unlike previous experiments, this experiment involved charged particles. The results were obtained using a DC SQUID in which the two junctions were separated vertically by about 7 cms. The junctions, which were phase-locked to an external microwave source, acted as two very precise batteries. Because of the gravitational red-shift of the radiation, a voltage difference of 1:10/sup 17/existed between these batteries, giving a net EMF in the SQUID loop in the absence of other effects of about 2x10/sup -21/volts. The loop EMF determined by the rate of change of flux in the loop was however less than 1x10/sup -22/volts, thus demonstrating the additional variation in the potential difference due to the gravitational field.         Long term operation of low noise DC-SQUID coupled to a very high Q gravitational radiation detector    C. Cosmelli, P. Carelli, M. Castellano and V. Foglietti Summary: We have coupled a very low noise dc-SQUID to the gravitational radiation detector of the Rome group at CERN laboratories. The SQUID used is a multiloop thin-film device with an input inductance of 1.6 /spl mu/H, loop inductance of 5 pH and coupling coefficient of 0.5. The gravitational radiation detector is composed by a 2.3 tons Aluminum cylinder mechanically coupled to a resonant capacitive transducer; this is matched to the SQUID by means of a large superconducting transformer. The signal to be detected is essentially composed by the two mode frequencies at about 1 kHz and with quality factors of the order of 4x10/sup 6/. To operate in a closed feedback loop mode we have used a particular setup in order not to degrade the performance of the system. The system operated for seven months with some interruptions due to refilling of liquid helium and various tests on the apparatus. The flux noise obtained was 1.5 to 3/spl times/ 10/sup -6/ /spl Phi//sub o///spl radic/Hz at 1 kHz with a linearity over 6 orders of magnitude and a long term stability of 1.5 /spl times/ 10/sup -8/ /spl Phi//sub o//hour.         Use of the Josephson junction in fundamental quantum electronics experiments    B. Yurke, L. Rupp and P. Kaminsky Summary: The Josephson junction provides two strong nonlinearities, the Josephson inductance utilized in parametric amplification and the sharp resistive knee used in SIS mixing. Both of these nonlinearities can be strong compared to a characteristic quantum current or voltage scale. This opens the possibility of using Josephson junctions to carry out fundamental experiments in quantum electronics that would be difficult or impossible to carry out at optical frequencies due to the lack of a correspondingly large nonlinearity in optical media. Here we propose a number of such experiments ranging from the generation of squeezed states with Josephson-parametric amplifiers to the generation of quantum-mechanical superpositions of macroscopically distinguishable states via Josephson-transmission lines. How the properties of such states can be investigated using SIS mixers will also be described. Squeezed states may be technologically useful in sensitive and precision measurement. How such states can be used to enhance interferometer sensitivity or reduce noise in phase sensitive measurement will also be described.         Measuring magnetic fluctuations from seismic waves using a superconductive gradiometer    P. Czipott and W. Podney Summary: We present a new application of superconductive magnetic gradiometry to a geophysical problem. Changing stresses in the earth's crust produce magnetic variations through the piezomagnetic effect. Seismic wave stress fluctuations cause magnetic variations measurable by a superconductive gradiometer. Their magnitude depends both on the wave stress and on the ambient stress. Measurements repeated over time can monitor changes in the ambient stress of magnetic strata near earthquake faults. Estimates of the signal size expected from the sources used in seismic surveying show that they comfortably exceed the sensitivity limits of present-day superconductive magnetic gradiometers. A first field trial of the method, conducted in the Whipple Mountains near Parker, AZ, in November 1985, shows magnetic gradient fluctuations several pT/m in amplitude coincident with the passage of seismic waves. However, ground motion can excite mechanical resonances in the gradiometer that contaminate the signal. The field trial points the way to refinements that lead to suppression of interference from ground motion.         Acoustic detection of single particles for neutrino experiments and dark matter searches    B. Neuhauser, B. Cabrera, C. Martoff and B. Young Summary: We are developing an entirely new type of particle detector, called a silicon crystal acoustic detector (SiCAD), which senses ballistic phonons generated when an incident particle collides with a nucleus or electron in a cube of crystalline silicon. For events which deposit energy greater than about 1 keV, a 1 kg SiCAD would have spatial resolution better than 1 mm/sup 3/and energy resolution better than 100 eV. We describe our laboratory research utilizing carbon thermistors, superconducting transition edge devices, and superconducting tunnel junctions as phonon sensors on the crystal faces.         Design and operation of SQUID-based planar gradiometers for non-destructive testing of ferromagnetic plates    R. Bain, G. Donaldson, S. Evanson and G. Hayward Summary: A planar second-order gradiometer coupled to a SQUID has been used with a persistent mode coil generating 0.02T perpendicular to a steel plate for the detection and characterisation of defects, such as cracks. We outline design criteria for the system, which is contact free, allows stand-off distances of up to 10cm, and can accommodate intervening media, both insulating (e.g. concrete) or conducting (e.g. sea-water or aluminium cladding). The sensitivity limit appears to be set by long-range permeability variations in the material of the plates, which may be due to unrelieved stress. We explain the use of digital filtering techniques to improve the resolution. Finally we discuss the use of higher-order gradiometers to improve the discrimination of localised defects from background variations.         SQUID technology applied to the study of electrochemical corrosion    J. Bellingham, M. MacVicar and M. Nisenoff Summary: Both the temporal and spatial dependences of the magnetic fields of electrochemical corrosion reactions have been investigated. A comparatively simple metal-electrolyte system, Zn in HCl, was chosen for concentrated study. Design of this corrosion cell, as well as its rationale, are described. The spectral density of the magnetic field generated by corrosion reactions has an inverse dependence on frequency. The overall noise level increases with increasing corrosion rate. These preliminary results confirm the great potential of SQUID magnetometry for the study of electrochemical corrosion phenomena.         Manufacture of keystoned flat superconducting cables for use in SSC dipoles    J. Royet and R. Scanlan Summary: The superconducting magnets used in the construction of particle accelerators are mostly built from flat, multistrand cables with rectangular or keystoned cross sections. In this paper we will emphasize the differences between the techniques for cabling conventional wires for cabling superconducting wires. Concepts for the tooling will be introduced. The effects of cabling parameters on critical current degradation are being evaluated in collaboration with NSS-Boulder. The results of these studies are presented in papers MH-6 and MH-8 at this conference.         Magnetic field measurements of model SSC dipoles    W. Hassenzahl, W. Gilbert, M. Green and P. Barale Summary: To qualify for use in the Superconducting Super Collider, the 8000 or so 16 m long dipole magnets must pass a series of tests. One of these will be a set of warm measurements of field quality, which must be precise to about 0.001% of the 100 G field produced by 10 A, the maximum current the coils are allowed to carry for an extended period at room temperature. Field measurements of better than this accuracy have already been carried out on 1 m long model dipoles. These measurements have included determinations of the dipole fields and the higher harmonics in the central or two dimensional region and in the total magnet. In addition, axial scans of the dipole and higher harmonic magnetic fields have been made to determine the local variations, which might reflect fabrication and assembly tolerances. This paper describes the equipment developed for these measurements, the results of a representative set of measurements of the central and integral fields and axial scans, and a comparison between warm and cold measurements. Reproducibility, accuracy and precision will be described for some of the measurements. The significance of the warm measurements as a part of the certification process for the SSC dipoles will be discussed.         A high field two mode superferric magnet    W. Xie, G. Phillips, W. Wenzel, H. Hinterberger and J. Briske Summary: We have designed and are building a high field Two-Mode (TM) superferric dipole magnet for particle accelerators. At low field it behaves as a ferric magnet while at high field as a cos/spl theta/ magnet. While the magnet can go up to any field as can a cos/spl theta/ magnet (limited by superconductor performance), the use of iron and rectangular rather than radial geometry retains the advantages of low field ferric magnets: substantial superconductor saving, more reliable operation, and easy fabrication.         Design, construction and test of a full scale SSC dipole magnet cryostat thermal model    R. Niemann, J. Carson, N. Engler, J. Gonczy, T. Nicol, J. Otavka, R. Powers and J. Theilacker Summary: As a part of the SSC main ring superconducting magnet development program, a full length dipole magnet thermal model has been constructed and its thermal performance measured. Presented are the details of the cryostat design and the thermal model construction experience and its evaluation. The methods for and the preliminary results of the thermal performance measurements are presented and compared with the predicted performance.         Results from heater-induced quenches of a 4.5 m reference design D dipole for the SSC    G. Ganetis and A. Prodell Summary: Quench studies were performed using a 4.5 m long Reference Design D, SSC dipole to determine the temperature rise of the magnet conductor during a quench by measuring the resistance of the conductor cable in the immediate vicinity of the quench. The single bore magnet was wound with improved NbTi conductor in a 2-layer cosine /spl theta/ coil configuration of 4.0 cm inner diameter. Eight pairs of voltage taps were installed at various locations on the right side of the inner coil of the magnet. "Spot" heaters were centrally located between the voltage taps of 4 of these pairs on the midplane turn of the inner coil to initiate magnet quenches. A redundant array of voltage taps and heaters was also installed on the left side of the inner coil. The resistance of the conductor was obtained from observations of the current and voltage during a magnet quench. The temperature of the conductor was then determined by comparing its resistance to an R vs T curve appropriate for the conductor. The quantity int I/sup 2/dt and the temperature, T, are presented as a function of current, and the maximum conductor temperature is shown as a function of int I/sup 2/dt. Measured longitudinal and azimuthal quench propagation velocities are also presented as a function of magnet current, and the temperatures at several locations on the inner magnet coil are plotted as a function of the time after a quench was initiated.         Results using active quench protection strip heaters on a reference design D SSC dipole magnet    G. Ganetis and A. Prodell Summary: Measurements were made with a Reference Design D SSC dipole magnet to study the quench behavior of the magnet when active quench protections trip heaters were used to initiate quenches. The magnet has a 2-layer cosine /spl theta/ coil configuration with a bore diameter of 4 cm and a length of 4.5 m. The strip heaters, their arrangement and installation are described. Three strip heaters individually and in combinations were used during these studies in the first series of which the magnet current was set at that value for which the quantity int I/sup 2/dt was maximum. A capacitor was discharged through the strip heater with the charging voltage being increased progressively until a magnet quench was inititated. The time interval between when the voltage was applied to the strip heater and when the magnet quench began was measured as was the time required for the voltage across the magnet coil that had quenched to reach 3V. These times and the quantity int I/sup 2/dt are presented for several values of charging voltage for different heaters and combinations of heaters. Curves of these times and int I/sup 2/dt as a function of magnet current at constant capacitance and voltage are also shown.         Transverse quench propagation measurement    M. Kuchnir, J. Carson, R. Hanft, P. Mazur, A. McInturff and J. Strait Summary: We have experimentally simulated the wedge regions of the winding of the Superconducting Super Collider dipole and studied the propagation of quenches in them. This study is relevant for proper selection and design of the quench protection scheme. The windings of these 16.6 m long dipoles incorporate copper wedges in order to achieve the required magnetic field uniformity, and the delay that they impose on the transverse spreading of normal zones is one of the needed data that we present here. Quenches under constant currents were triggered with spot heaters, and their development recorded from voltage taps strategically located. Currents as high as 6 kA were used. Under zero magnetic field conditions the delays are too long for self-protecting schemes.         Control of the fields due to superconductor magnetization in the SSC magnets    M. Green Summary: Field uniformity of better than one part in 10,000 is required for the dipole magnets for the Superconducting Super Collider (SSC). The high field dipole and quadrupole magnets proposed for the SSC generate higher multipole components of field due to magnetization (persistent currents) in the superconductor. When the superconductor filament diameter is of the order of 20/spl mu/m, the sextupole term alone is about 17 parts in 10,000 at an injection induction of 0.3 tesla in the SSC dipole magnets at a radius of 1 cm. This paper shows calculations of the magnetization phenomena which agree very well with magnetic measurement. Several passive methods for removing the sextupole component and higher components of the field generated by magnetization of the superconductor in the SSC dipole magnets are presented in the paper.         The effects of filament magnetization in superconducting magnets as calculated by poisson    S. Caspi, W. Gilbert, M. Helm and L. Laslett Summary: Magnetization of superconducting material can be introduced into POISSON through a field dependent permeability table (in the same way that iron characteristics are introduced). This can be done by representing measured magnetization data of the increasing and decreasing field by two independent B-/spl gamma/ curves (/spl gamma/ = 1//spl mu/). Magnetization curves of this type were incorporated into the current regions of the program POISSON and their effect on the field coefficients observed. We have used this technique to calculate the effect of magnetization on the multipole coefficients of a SSC superconducting dipole magnet and to compare these coefficients with measured values.         A novel, elegant method for passive compensation of magnetization-current-induced field errors in the CERN LHC 10 T superconducting dipole magnets by permanent multipole magnets    A. Asner Summary: CERN is at present studying a Large Hadron Collider --LHC- with some 1'600 up to 12 m long 10 T-, twin bore, high field uperconducting dipoles to be eventually installed in the 27 km tunnel of the e/sup +/-e/sup -/collider, the LEP machine, actually under construction. In these dipoles the largest magnetic field error perturbing the particle closed orbit at 0.5 T injection field into the LHC, is caused by magnetization currents in the NbTi/sub 1.8K/or Nb/sub 3/sn/sub 4.5K/filaments of expected 10 /spl mu/m diameter. To compensate this negative 1.9 O/oo relative sextupole error at 3 cm bore diameter, a novel, elegant and inexpensive method is proposed ; one could either place a continuous, thin and concentric permanent sextupole layer within each 12 m long S.C. dipole or referably insert two short lumped correctors at its ends. To determine the compensation efficiency, systematic and random errors of the magnetization current effect in the S.C. windings and error sources in the permanent sextupole correctors due to geometrical, magnetic and temperature inlluences as well as to the interplay with the main dipole field are considered, taking notably into account that the correctors will have to operate at liquid helium temperature. Low temperature measurements on samples of permanent SmCo and NdBFe magnets indicate consistant and interesting improvement in the remanent field B/sub r/of about 7 %, excellent reproducibility of B/sub r/to a few 10/sup -4/at LN/sub 2/, and LHe temperatures as well as very good mechanical behaviour. Low temperature sample measurements in external and opposed dipole fields up to 1.9 T resulted in a remanent field reduction of -AB/sub r//B/sub r/= - 5.7 %. Reducing the opposed dipole field to zero, a permanent demagnetization effect of - 2.5 % remained. Based on computations, mechanical properties and low temperature permanent magnet sample measurements, the proposed compensation of magnetization current induced error in windings of superconducting magnets is entirely feasible ; an error reduction factor of3..5 can be expected. A correcting permanent sextupole prototype magnet has been ordered and will be completely tested.         Monitoring the magnetic properties of iron for large scale production of superferric magnets    M. Davidson and W. MacKay Summary: An automated system for measuring critical ferromagnetic properties of iron sections of superferric magnets from low to high magnetic intensities has been developed and used at the Texas Accelerator Center in conjunction with the construction of the superferric SSC magnet prototypes. The system is readily adaptable to production line measurements and would be an indispensable quality control tool in the construction of production steel lamination cores for superferric systems, such as particle accelerators.         A 3 tesla superconducting solenoid for the AMY particle detector at TRISTAN    K. Tsuchiya, S. Terada, A. Maki, T. Omori, S. Ishimoto, H. Hirabayashi, S. Olsen, K. Asano, I. Kurita, H. Hashimoto, K. Aihara, R. Saito and T. Suzuki Summary: A high field superconducting solenoid for the AMY particle detector at the TRISTAN storage ring at KEK was designed and constructad. It consists of an 8 layer superconducting solenoidal coil placed in s thick hexagonal iron return yoke. The solenoid has a 2.39 m inner coil diameter and is 1.54 m in overall length with a radial thickness of 0.1 m. The design current and field at the center are 5000 A and 3 T, respectively. The stored energy in the field is 40 MJ. Initial magnet test data are given.         Construction and testing of A /spl plusmn/ 16/spl deg/ superconducting beamline magnet    J. DeKamp, C. Magsig, J. Nolen and A. Zeller Summary: A prototype of the beamline switching magnets needed for operation of the National Superconducting Cyclotron Lab's 1.6 GeV/c heavy ion beam transport system has been constructed and is undergoing tests. The device features a compact design, as well as good cryogenic and magnetic efficiency. In the operational range of 1.0 to 1.75 T the required field uniformity of /spl plusmn/ 0.1% has been obtained. The design current density in the potted coils is 17 kA/cm/sup 2/at 1.75 T, and the magnet has operated at a current density of 20 kA/cm/sup 2/at 1.8 T without a quench.         The 5 cm aperture dipole studies    A. McInturff, R. Bossert, J. Carson, H. Fisk, R. Hanft, M. Kuchnir, R. Lundy, P. Mantsch and J. Strait Summary: The results obtained during the evolution of the design, construction, and testing program of the design "B" dipole, are presented here. Design "B" is one of the original three competing designs for the Superconducting Super Collider "SSC" arc dipoles. The latest design "B" cross-section The final design parameters were as follows: air cored (less than a few percent of the magnetic field derived from any iron present), aluminum collared, two layered winding, 5.5T maximum operating field, and a 5cm cold aperture. There have been fourteen 64cm long 5cm aperture model dipoles cold tested (at 4.3K and less) in this program so far. There was a half length full size (6m) mechanical analog (M-10) built and tested to check the cryostat's mechanical design under ramping and quench conditions. Several deviations from the 'Tevatron' dipole fabrication technique were incorporated, for example the use of aluminum collars instead of stainless steel. The winding technique variations explored were "dry winding," a technique with the cable covered with Kapton insulation only and "wet winding" where the Kapton was covered with a light coat of "B" stage epoxy. Test data include quench currents, field quality (Fourier multipole co-efficients), coil magnetization, conductor current performance, and coil loading. Quench current, loss per cycle, and harmonics were measured as a function of the magnitude and rate of change of the magnetic field, and helium bath temperature.         Pulsed magnetic energy storage for space applications    M. Abdelsalam and Y. Eyssa Summary: Toroidal energy storage magnets can be used as power supplies for many space applications. Their list of advantages include high efficiency, light weight, zero stray magnetic field, zero electro-magnetic radiation, and fast pulsing. Superconducting toroidal field coils with an inner small cryoresistive shield are proposed. Both the superconducting coil and the cryoresistive coil are connected in parallel. Their configuration is such that energy pulses are drawn mainly from the resistive coil, while the superconductive coil is shielded from the resulting AC field and current produced. The relationships between system parameters, such as coil dimensions, ampere meters, coil surface area and structural mass on one side, and the coil aspect ratio, stored energy and maximum field on the other side are derived for toroidal coils in rectangular and bending free D-shaped configurations.         Friction analysis for a nonrippled superconducting energy storage structure    X. Huang Summary: Two-layer low aspect ratio solenoids mounted in surface trenches are described for superconductive magnetic energy storage utility applications. A new two-layer nonrippled SMES design, in addition to rippled designs, is under study. This design has 257 two-turn pancakes. Each structure piece consists of an extruded trough, with the NbTi-AL conductor lying on its outer edge, and a simple rectangular plank. Troughs and planks are 5 meters long and overlap one another. Problems related to friction forces between troughs and planks and between conductors and troughs are considered in this study. Friction forces during cooldown, normal operations of charge and discharge, and emergency energy dump are covered. These problems are modeled by two-dimensional plates with appropriate boundary conditions. Euler's equation is employed to derive the governing equations for the friction forces. Solutions snow that the structure will slip and lock when needed due to friction and other forces.         Experimental study on stabilization of model power transmission system by using four quadrant active and reactive power control by SMES    Y. Mitani, Y. Murakami and K. Tsuji Summary: This paper presents the experimental results of stabilization of a model power transmission system by using a Superconducting Magnet Energy Storage (SMES). The SMES, which was composed of two sets of GTO (Gate Turn Off thyristor) power converters and a superconducting coil, is capable of controlling active power (P) and reactive power (Q) simultaneously in four quadrants by changing the firing angles of power converters. The model power transmission system was designed to simulate the behavior of a real scale long distance bulk power transmission system with voltage of 500 kV, capacity of 2000 MVA and length of 280 km. In this study, we have experimented power system stabilizing control by applying P-Q simultaneous control ability of SMES. From the results of experiment it was demonstrated that stabilizing effect by means of SMES is very significant.         Charging and discharging characteristics of SMES with active filter in transmission system    T. Ise, Y. Murakami and K. Tsuji Summary: For SMES (Superconducting Magnet Energy Storage) composed of Superconducting Magnet (SM) and thyristor converters, the harmonic currents which are generated by SMES converter should be compensated. We have developed active filter, the output of which is adaptively controlled such that the deviation of the waveform of ac line current from the sinusoidal one can be cancelled out. SMES system composed of two sets of GTO (Gate Turn-Off) thyristor converter, 0.5 MJ pulsed SM which are controlled by a direct digital controller, and the active filter, has been developed. The SMES system has been connected to a model power transmission system together with a 10 kVA generator. The controlled characteristics of SMES in the model power transmission system and compensated characteristics of active filter have been experimentally studied. The experimental results show that harmonic currents of SMES can be successfully compensated by active filter, and simultaneous active and reactive power control of SMES can be carried out without the influence of harmonic distortion.         The conceptual design of utility-scale SMES    M. Masuda and T. Shintomi Summary: In this paper the design study of a commercial 5 GWh unit in Japan is described, especially emphasized on the superconducting coil system.         A superconducting pulse magnet for energy storage and its nonmetallic cryostat    J.-T. Eriksson, O. Kauppinen, R. Mikkonen and L. Soderlund Summary: The work is a step towards superconducting power applications e.g. diurnal storage. The energy of the vertically mounted solenoid coil is charged and discharged by a 6-pulse thyristor bridge. Filters are omitted in order to obtain high response of energy transfer. The ramping rate is about 8 T/s, and the central field is 2 T at 250 A. The superconducting wire has a diameter of 1.3 mm and a Cu/CuNi/NbTi mixed matrix for decreasing ac losses. Effective cooling is provided with spacers forming wide vertical cooling channels between layers. To minimize eddy current losses and to avoid excessive boiling of liquid helium a nonmetallic cryostat is used.         Development of 50 Hz disc-type superconducting coil    M. Yamamoto, M. Ikeda, Y. Tanaka, K. Matsumoto, T. Ishigohka and O. Tsukamoto Summary: Two experimental superconducting coils for AC application are made. Both coils are disc-type and epoxy-impregnated. They are wound by a conductor made of multifilamentary NbTi composite wire with very fine filaments. The excitation characteristics and the AC losses are measured. The induced peak field is 0.75T at the peak current of 164A, and the rating of the coil is about 4kVA.         Heat transfer in helium II for two-layer energy storage magnets    Y. Eyssa, X. Huang and J. Waynert Summary: The stability of He-II-cooled multilayer magnets usually is limited because of the finite amount of helium close to each conductor, For such cases, the heat flux at the conductor surface falls steadily with time following a normal zone initiation. For full cryogenic stability in large coils, such as magnetic energy storage magnets, the heat conduction capacity to He II should be larger than the I/sup 2/R heat produced in a normal conductor on a continuous basis, providing recovery from large initial normalizing heat pulses. Using both finite element and finite difference techniques, the heat conduction equation for two-layer coils in He II is solved for both steady-state and transient conditions in two dimensions to yield the heat flux at the conductor surface and the total enthalpy absorbed by He II at any time. Two-layer coils are specified so that all conductors in each layer share a common bath of helium. Solutions are given for different normal-zone lengths at different positions in the coil. Heat fluxes at the surface of the conductor as high as 2.5 watt/cm/sup 2/can be cooled for a long time (t>200 sec.).         A 17 tesla superconducting magnet with multifilamentary superconductors    M. Takeo, K. Funaki, S. Sato, K. Yamafuji, M. Iwakuma, M. Hiramatsu, K. Matsumoto and M. Hamada Summary: We constructed a superconducting magnet with an inner diameter of 110mm, outside diameter of 720mm, and 750mm in height, wound from multifilamentary superconductors using a react-and-wind method in the Research Institute of Superconducting Magnet [RISM] of Kyushu University. While we succeeded in energizing this magnet up to 16.2 tesla and 6.3MJ at 4.2K without a quench early this year, we further fabricated an insert booster magnet to get a higher magnetic field. This insert booster magnet was wound from a Nb/sub 3/Sn(+Ti) conductor in a wind-and-react method, because the dimensions were only 34mm for inner bore, 98mm for outerside dimameter and 192mm in height. When this magnet was installed in the above-mentioned magnet, the whole magnet produced 17.1 tesla at 4.2K without quenching, which is a new record as a magnet made of multifilamentary conductors.         Test of the GA 12 T model coil at 4.2 K and with helium II    Y. Hsu, J. Alcorn, J. Purcell, J. Kerns and M. Chaplin Summary: A 0.4m I.D. X 1m O.D. superconducting coil for the DOE 12 Tesla Coil Program was tested at the LLNL High Field Test Facility (HFTF). Cabled NbTiTa conductor bath-cooled with liquid helium was employed. Three operating modes, defined by the coolant state, were planned: Case I - 4.2 K, saturated at 1 atm; Case II - 1.8 K, saturated at 12.5 torr; and Case III - 1.8 K at 1 atm. Due to limited lHe capacity of the LLNL refrigerator/reservoir system relative to the LLNL HFTF cryostat boiloff rate, only two cases were tested. Without the background field coils, the GA coil was energized to 10 kA without a quench. At 4.2 K and a background field of 8 tesla, the GA coil quenched at 4 kA at a maximum field of 9.15 T. In Case III (1.8 K) with a background field of 8.5 tesla, the GA coil quenched at 8 kA, at a maximum field of 10.75 T. The conductor development background, coil structure, coil test setup, test results and analysis are presented and discussed. The cause of the quench at less than 12 T appears to be incomplete mixing of the NbTiTa alloy during the crucible melt.         Applicability of superconducting magnet to high gradient magnetic separator    S. Nishijima, K. Takahata, K. Saito, T. Okada, S. Nakagawa and M. Yoshiwa Summary: The applicability of superconducting magnets to high gradient magnetic separators has been studied experimentally. It has been confirmed that weakly paramagnetic materials could be separated efficiently using high magnetic field, generated by superconducting magnets. The industrial application is possible for purification or decontamination of water since the flow rate and the extracting coefficient could be increased by high field.         A small Nb/sub 3/Ge test solenoid    V. Cernusko, M. Jergel, K. Frohlich and M. Polak Summary: Behaviour and properties of a small test solenoid made from a long piece of stabilized Nb/sub 3/Ge superconductor prepared by the CVD method are described. The used CVD apparatus allows to prepare continuously pieces of more than 200 m in length. A total length of 43.5 m of the 61 m long Nb/sub 3/Ge tape has been used for a construction of a test solenoid. The solenoid properties were measured in an outside magnetic field produced by 40 mm bore superconducting magnet. The contribution of the test solenoid was 0.84 T in the total magnetic field of 4.35 T and 0.42 T in the total field of 9.25 T.         Contact resistance of demountable multi-pin joint for superconducting helical coil    T. Horiuchi, Y. Monju, N. Suzuki, T. Kawai, M. Hamada, K. Inoue, K. Uo and O. Motojima Summary: We designed an "Inserting Multi-Pin Joint" for a superconductor to realize a demountable superconducting helical coil for the heliotron fusion reactor. The relation between contact resistance and contact pressure was investigated using multi- and single-taper-pin inserting joints. These taper pins were plated with 5/spl sim/50/spl mu/m thick indium. The minimum contact resistance at 7T was 6x10/sup -9//spl Omega/cm/sup 2/in a single-joint sample and 9x10/sup -9//spl Omega/cm/sup 2/in a multi-joint with 300MPa contact pressure. This contact resistance ratio of multi-joint to single-joint agreed with the theoretically calculated value. In the reactor model Heliotron F with 3.5GJ magnetic energy, total joule loss due to the contact resistance of the joint was estimated at 4.8kW, which was small in comparison to the total cooling power of about 10.8kW. These results suggest the possibility of applying a tapered pin inserting joint to the superconducting helical coil.         Current distribution in a moving spot flux pump    O. Mawardi and Tae Ko Summary: A theoretical investigation for the distribution of the current around a moving spot in a flux pump has been analyzed. A quasi-static approach has been used to obtain the governing equations for the current distribution. Numerical solutions of these equations by means of a successive over-relaxation technique yields the location of the normal spot in the flux pump at which the current ahead of the moving spot jumps to the back of the spot. The results of these calculations are used to interpret the drooping voltage-current characteristics of flux pumps, as well as, the occurrence of parasitic oscillations.         Armature reaction in a flux pump    O. Mawardi and Shangang Xu Summary: The self-inductance of a rotating spot flux pump is responsible for the drop of output voltage from the pump. The magnitude of this effect referred to as the "armature reaction" has been studied in this paper. It is shown that this reaction is a function of the current generated, the speed of rotation, and the shape of the magnetic poles used in the excitation of the pump. A few suggestions have been given for the construction of pumps with reduced armature reaction.         Decoupled control techniques for dual flying capacitor bridge power supplies of large superconductive magnets    M. Ehsani, A. Hozhabri and R. Kustom Summary: The dual flying capacitor (DFC) was developed in 1976 as a method of supplying efficient bilateral power to large superconductive magnets. This power supply concept uses a second superconductive coil for energy storage. Large reversable power demands of the load magnet are met by energy exchange between the storage and load coils, through the DFC bridge. This paper will show that the DFC circuit can be decomposed into two elementary single flying capacitor (SLC) circuits which can be controlled independently. The discovery of this decoupled control concept is the origin of several new control strategies which significantly improve the performance of DFC power supplies, microcomputer controllers containing the decoupled control algorithm were tested on a DFC system simulator. The results show that time optimal load coil current and voltage control is now achievable by a robust bang-bang control technique. Furthermore, load coil current ripple and voltage spectrum can be independently controlled, while following an arbitrary reference signal. The DFC bridge, with the decoupled controllers, is a high performance power supply candidate for superconductive magnets of fusion reactors, particle accelerators and other systems.         A high-power magnetically switched superconducting rectifier operating at 5 Hz    G. Mulder, H. Krooshoop, A. Nijhuis, H. ten Kate and L. van de Klundert Summary: Above a certain current level, the use of a superconducting rectifier as a cryogenic current source offers advantages compared to the use of a power supply at room temperature which requires large current feed-throughs into the cryostat. In some cases, the power of such a rectifier is immaterial, for example if it is to be used as a current supply for short test samples with low inductances. Usually, however, a rectifier is intended to energize large superconducting magnets, so the maximum power available becomes an important parameter since it determines the loading time. One method of increasing the power of a rectifier is to raise the operating frequency. In this respect, magnetically controlled switches with very fast switching times are preferable to thermally controlled ones. This paper reports on the design, as well as the experimental results of a magnetically switched full-wave superconducting rectifier. Once this rectifier is brought to its design frequency of 5 Hz, the average power delivered to the cryogenic load will be 500 W.         Shape optimization of iron shield for superconducting solenoid magnets    A. Ishiyama, S. Kanda, H. Karasawa and T. Onuki Summary: The superconducting solenoid magnet for high energy physics or the MRI systems use the iron shield to enhance the central field or to shield the strong leakage magnetic field. But the design technique of the iron shape has not been established, since the iron has nonlinear permeabillty. In the present paper, a optimizing procedure of the iron shield shape is proposed. Our procedure is based on the hybrid finite element-boundary element method(HFB method). The HFB method is suited to analysis of problem which present nonlinear behavior and extend to infinity. The HFB method may facilitate to optimize the shape of the nolinear iron shield.         Optimal design of superconducting magnets for whole-body NMR imaging    A. Ishiyama, T. Yokoi, S. Takamori and T. Onuki Summary: A new optimal design technique of magnetic field systems, which utilizes a coupling procedure of the hybrid finite element-boundary element method (HFB method) and the mathematical programming, is proposed. This technique is applied to the design of the high homogeneous field superconducting magnet system with the environmental shield for whole-body NMR imaging. Results of the optimal design for three 1.0-tesla-magnet systems with different types of shields (an iron shield, a shield magnet, and a combination of the iron shield and the shield magnet) are shown.         Precise Hall measurements at 4.2 K in superconducting magnets    J. Cornelis, F. Biermans, N. Maene and A. Van den Bosch Summary: In recent years our Institute has acquired the know-how for wet-winding and testing NbTi superconductive coils. For the determination of the magnetic fields Hall sensors are found to be very convenient. To increase the precision on the Hall measurements a computer controlled Hall current chopping and reversing circuit has been used. The analysis of the data showed that the Hall voltage is essentially proportional to the magnet current. A small, less than 0.5 percent, oscillatory term appears which is clearly resolved above 2 tesla and which is reproducible during each cooling cycle. The amplitude of the oscillatory term is proportional to the magnet current intensity and the phase is a linear function of the reciprocal magnet current intensity. The oscillatory behaviour has been measured on different Hall probes, the fitting parameters being characteristic for each probe. Similar oscillations were measured on the current contacts of the Hall sensor, showing the Shubnikov-de Haas effect. The sensitivity of our Hall measuring device is 0.1 mT, The resolution is high enough to reveal, on the magnet axis, small remanent field differences of maximum 6.7 mT after the magnet had been energized to 8 tesla. The persistent field at the centre of the magnet is lower than 2 mT. The Hall measurements on the superconductive S.C.K./C.E.N. magnet allowed the determination of a precise relationship of field versus Hall voltage.         Magnetic shielding network with superconducting wires    S. Nishijima, K. Takahata, I. Miyamoto, T. Okada, S. Nakagawa and M. Yoshiwa Summary: Magnetic shielding networks have been studied, aiming at a practical use of superconducting shields against high and pulsed magnetic fields. The NbTi multifilamentary composite wires were chosen for the shielding material because they show high magnetic stabilities against pulsed fields compared with those of the bulky superconductors. The shielding networks in the shape of cylinders and plates were made by soldering the junctions of wires. The static and pulsed magnetic fields, of which maximum field was 3T, were applied to the shieldings, and the field distributions inside and outside of the shielding were measured. It was confirmed experimentally that the superconducting networks showed high shielding efficiency and capability of shielding the magnetic field with complicated distribution.         The CEBAF superconducting accelerator cryomodule    G. Biallas, P. Brindza, C. Rode and L. Phillips Summary: The design and fabrication of the cavity enclosure and calculation to support the 2/spl deg/K operating temperature, and techniques for minimizing operating heat loads and cryostat loads are discussed: The integrating of the cryogen fluid distribution system into the cavity cryostat will be presented. Integration of the cavity design into cavity fabrication and maintenance program, with emphasis on system reliability and flexibility, is included.         An optimized input waveguide for the CEBAF superconducting Linac Cavity    P. Brindza, G. Biallas and L. Phillips Summary: A thermally optimized input waveguide for the CEBAF Superconducting Linac Cavity, to operate at 2.0K, has been designed. Calculations leading to thermal optimization including conduction, specularly reflected radiation and RF power dissipation are presented. An economic comparison between a thermal intercept and continuous counter flow cooling has been made. Calculations and techniques for reducing specularly reflected radiation are discussed.         Field quality of the end sections of SSC dipoles    W. Hassenzahl, S. Caspi, W. Gilbert, M. Helm, L. Laslett and G. Morgan Summary: The central or two-dimensional field of a dipole magnet can be calculated with some precision. The fields at the end of the magnet, which are three-dimensional in nature, provide a more complicated problem. Starting with an end design that produced a relatively good end in terms of multipole components, a method of extending parts of the straight section was used to reduce the most important harmonics, the sextupole and decapole, to a negligible level. In addition, the effect of extending an iron yoke over the ends of a magnet was investigated and it was found to have little effect on the harmonics, though it will raise the dipole field. These results are encouraging as they imply that good ends can be developed with relative ease should the two dimensional cross-section of a dipole magnet such as the SSC have to be changed.         Nb/sub 3/Sn composite with distributed internal Sn    K. Marken, S. Hong, W. Marancik, G. Grabinsky, D. Pattanayak and F. Lewicki Summary: This paper describes the results of one of many Nb/sub 3/Sn multifilamentary composites we are currently investigating. The wire is fabricated with so called "internal Sn methods". The Sn is distributed between the filaments rather than the center of wire in order to shorten the Sn diffusion distance and utilize the space in the wire effectively. A 6 micron thick uniform fine grain Nb/sub 3/Sn layer has been produced with a diffusion heat treatment temperature of 680/spl deg/C. A critical current density of 2290 A/mm/sup 2/(10 T, 4.2 K, 10/sup -14//spl Omega/M) was attained.         Effects of titanium addition to the Nb/sub 3/Sn wires fabricated by the internal tin diffusion process    S. Miyashita, K. Yoshizaki, Y. Hashimoto, H. Sekine and K. Tachikawa Summary: The titanium-doped Nb/sub 3/Sn wires have been successfuly fabricated by the internal tin diffusion process (IDP). These wires consist of a Sn-4.8 at%Ti alloy core at the center and 99 pure niobium and/or Nb-1.9at%Ti alloy filaments placed in three layers around the Sn-Ti core. These wires were easily drawn to the final sizes without any intermediate annealing, and were heat treated at 650-750/spl deg/C for 30 - 300 hr. The Electron Probe Micro Analysis analysis (EPMA) has revealed that, when the titanium is added only to the tin core, the titanium content in Nb/sub 3/Sn filaments decreases with increasing distance from the center of the wire. On the other hand, the simultaneous titanium addition to the tin core and two outer layers of niobium filaments has attained the uniformity of the titanium content; /spl sim/ 0.8at%Ti is incorporated in all Nb/sub 3/Sn filaments. The overall J/sub c/of /spl sim/ 4 /spl times/ 10/sup 4/A/cm/sup 2/at 15 T and the improved B/sub c2/have been obtained for the Nb/sub 3/Sn wires with the simultaneous titanium addition. These results indicate that the IDP Nb/sub 3/Sn wires with simultaneous titanium addition to the tin core and niobium filaments are the most promising candidate materials for high field magnets.         Effect of titanium additions to in-situ Nb/sub 3/Sn wire    P. Quincey and D. Dew-Hughes Summary: Multifilamentary Nb/sub 3/Sn wires have been prepared by solid state diffusion starting from in-situ cast ingots of Cu plus 30 wt.% Nb. Oxygen contamination was found to have an adverse effect on both the processing and the superconducting performance at high fields of the final wire. In an attempt to divert oxygen from the Nb, a small amount (1 wt.%) of Ti was added to the melt. Processing of the ingot was improved, the final wire consisting of fine, regular ribbonlike filaments. Additions of Al, Hf and Zr were found to have a similar effect. Critical current measurements were made at 4.2 K in inductions up to 15T on wire after tin-plating and reaction. Above 1OT, critical current densities for wires containing Ti were higher than those for wires with no additions. Kramer plots extrapolated to B/sub c2/> 21T. It is seen that the addition of Ti to in-situ Nb/sub 3/Sn improves both the processing and the high field Superconducting performance.         High-field superconducting critical values of titanium bronze multifilamentary Nb/sub 3/Sn conductors    K. Kamata, H. Moriai, N. Tada, K. Watanabe, A. Nagata and K. Noto Summary: Multifilamentary Nb/Cu-7.5at%Sn-0.4at%Ti wires with two kinds of configurations were fabricated and their superconducting properties were evaluated. One kind of wires contain 1 /spl sim/ 5 /spl mu/m-diam 31 X 361-Nb cores. These wires composed of our typical configuration with each 361-Nb cores embedded in a Cu-7.5Sn-0.4Ti matrix inside a Nb barrier, surrounded by a stabilizing Cu. The other kind of wire contains 4.7/spl mu/m-diam 721-Nb cores in a Cu-7.5Sn-0.4Ti matrix inside a Nb barrier surrounded by a stabilizing Cu. The latter wire showed higher J/sub c/(overall) than the wire with the former configuration of about the same core diameter. The J/sub c/(overall) at 15 T exceeded 400 A/mm/sup 2/at 4.2 K and reached to 570 A/mm/sup 2/at 1.8 K for the latter wire heat treated at 650/spl deg/C for 200 hr. While the 4.6/spl mu/m-diam core wire with the former configuration showed a J/sub c/(overall) of 350 A/mm/sup 2/at 15 T, 4.2 K after the heat treatment at 660/spl deg/C for 200 hr, it also reached to 400 A/mm/sup 2/at 15 T, 4.2 K when the core diameter was reduced to 2.7/spl mu/m and heat treated at comparatively low temperature of 640/spl deg/C for 200 hr. The H/sub c/2's at 4.2 K were extrapolated to about 25 T for both kinds of wires. Since the T/sub c/'s were measured to be 16.8 K for these two kinds of wires, this H/sub c/2 enhancement may be attributed to the /spl rho/n increase as a result of Ti incorporation into the Nb/sub 3/Sn layer in the same way as that for Nb-Ti core Nb/sub 3/Sn wires.         Laser and electron beam processing of superconductors    K. Tachikawa and K. Togano Summary: Scanning irradiations using high power density beams of CW-CO/sub 2/lasers and electrons have been applied for the fabrication of superconducting Nb/sub 3/Ga, Nb/sub 3/Al and Nb/sub 3/(Al,Ge) conductors. The materials to be irradiated were prepared in tape form and the scanning was carried out by moving the material in a stationary beam with the intension of future development to industrial applications. For the formation of Nb/sub 3/Ga, a tape composed of NbGa/sub 3/compound layer on the Nb substrate was prepared by a continuous dipping process. The laser irradiation successfully produced a new layer containing A15 Nb/sub 3/Ga by alloying the NbGa/sub 3/layer and a portion of the underlying Nb substrate. The highest T/sub c/attained by the irradiatioh is 15.9K (midpoint), and is increased to 18.2K by the following low temperature annealing at 700/spl deg/C. Nb/sub 3/Al and Nb/sub 3/(Al,Ge) tape conductors were also fabricated by laser and electron beam scanning irradiations onto Nb-Al and Nb-Al-Ge composite tapes prepared by the conventional powder metallurgy method. The laser irradiation directly onto the Nb-Al composite produced a molten and then rapidly resolidified zone composed of /spl alpha/-Nb dendrite and A15 Nb/sub 3/Al. The T/sub c/values are well over 16K, which can be increased by 1-2K by the subsequent annealing. A maximum J/sub c/for reacted zone of 4.8x10/sup 4/A/cm/sup 2/was obtained at 23T and 4.2K. In order to minimize the loss of Al, the irradiation onto Nb-sheathed Nb-Al and Nb-Al-Ge composites was also carried out using both laser and electron beams. The J/sub c/increases with increasing power density until the melting including Nb-sheath occurs, and then rapidly decreases at higher power densities due to the decrease of A15 volume fraction. The Nb/sub 3/Al and Nb/sub 3/(Al,Ge) tapes processed under proper conditions show excellent high field properties, the J/sub c/exceeding well over 10/sup 4/A/cm/sup 2/in magnetic fields up to 23T. Compared with the electron beam irradiation, the laser beam irradiation has a disadvantage that the absorption coefficient of energy into the material is sensitive to surface conditions neccesitating special care in handling the material surface. However, in the case of laser irradiation, operation in the pressurized atmosphere is possible, which is very effective to minimize the loss of volatile elements such as Al,Ga. In order to study the feasibility to large scale production, new continuous irradiation systems have been installed for both CW-CO/sub 2/laser and electron, and the examinations to fabricate longer tapes of 10-100m are now in progress.         Preparation of A15 Nb/sub 3/Ge tape by a single-roller rapid quenching technique    Y. Kubo, A. Kamijo, T. Yoshitake and H. Igarashi Summary: We have Prepared a high Tc Nb/sub 3/Ge tape by using a single-roller rapid quenching apparatus specially made for high melting point alloy applications. The rapid quenching of Nb/sub 3/Ge produced amorphous ribbons for compositions at Ge = 21 /spl sim/ 27at %. Heat-treatment at 700/spl deg/c for 100 hours converted these amorphous ribbons into nearly single phase A15 (Ge = 21 /spl sim/ 24at.%) and A15+Nb/sub 2/Ge/sub 3/(Ge = 25 /spl sim/ 27at.%). The superconducting transition temperature Tc was about 4K for the amorphous phase, While the heat-treatment improved Tc values considerably; the highest Tc value, 18.3K(onset) with /spl utri/Tc=0.6K, was obtained from Ge=23at.%.         Improved critical current densities in Nb/sub 3/Al based conductors    R. Bruzzese, N. Sacchetti, M. Spadoni, G. Barani, G. Donati and S. Ceresara Summary: By reducing substantially the thickness of the Nb and Al reacting layers, very high current densities (J/sub c/= 1.8x10/sup 9/A/m/sup 2/at 11 T and 4.2k) have been I T and 4.2 K) have been achieved in Nb/sub 3/Al single-core conductors produced by the jelly-roll approach. This impressive improvement of J/sub c/is larger than expected from previous results which correlate critical current densities with the thickness of the layered structure. The present characteristics of commercial Nb thin foils do not allow very high J/sub c/multifilamentary wires to be produced by the jelly-roll process, since a recrystallized 10-20 /spl mu/m Nb foil containing less than 50 ppm of oxygen would be required. However, a new process, the intrinsic multifilamentary approach, IMF/sup 10/, has been set up to obtain a multifilamentary wire by using commercial Nb thin sheets. According to this method, some IMF samples have been produced with critical current densities somewhat lower than the density of the jelly-roll conductors but comparable with Nb/sub 3/Sn conductors. Improvements are still possible in order to approach the jelly-roll results. The effective filament diameters of IMF conductors, determined by magnetization measurements, are around 20 /spl mu/m, suggesting that among the Nb/sub 3/Al thin sheets there are some contacts, while some unreacted Nb could provide barriers in the radial direction. Similar measurements on monofilamentary jelly-roll conductors are in progress.         Powder metallurgical alternative for the processing of (Nb - Ta)/sub 3/Sn multifilamentary wires, starting from elementary Nb and Ta powder    S. Gauss and R. Flukiger Summary: Ordinarily the Nb-Ta cores of alloyed Nb/sub 3/Sn wires are prepared by electron beam melting followed by remelting for better homogenity. The present work describes the first attempt to replace the melting process by a more economical powder metallurgical technique, starting with Nb and Ta elementary powders. After the processing to fine wires, the ductile Ta particles are deformed to ribbon-like filaments, the average distance between two Ta "Walls'' being in the range of the A15 grain size. Thus an improvement of the pinning behavior of Nb/sub 3/Sn multilfilamentary wires was expected. Nb/Ta powde mixtures (up tp 20 wt Z Ta) were extruded and deformed to rods. wich were inserted in a bronze matrix, the superconductor wires being produced by the conventional bronze route. It was found that during the reaction heat treatment Ta is partly dissolved in the A15 layer, the dissolved amount depending strongly on the reaction temperature. As a main result of the present investigation, the field dependence of J/sub c/for our wires after a reaction of 120 h at 675/spl deg/C is similar to that of binary Nb/sub 3/Sn wires, the absolute value of J/sub c/below 13 T being substantially higher than that of the latter. After 64 h at 700/spl deg/c and 750/spl deg/c, J/sub c/has the characteristics of alloyed Nb/sub 3/Sn wires the absolute values of J/sub c/in the A15 phase being comparable to those of the best conventionally processed (Nb-Ta)/sub 3/Sn wires. These high critical currents after the reaction at T /spl les/ 675/spl deg/C are discussed as a consequence of "artifical pinning" by the remaining Ta inclusions.         21 Tesla powder metallurgy processed Nb/sub 3/Sn(Ti) using (Nb-1.2 wt%Ti) powders    S. Pourrahimi, C. Thieme and S. Foner Summary: Powder metallurgy (P/M) processed Nb/sub 3/Sn(Ti) wires were made with alloyed Nb(Nb-1.2wt%Ti) powders using a Cu-45wt% (Nb-1.2wt%Ti) composite. Nominal areal reductions of about 10/sup 4/were used and Sn was introduced by means of a central Sn core. With a Sn-5wt%Cu core a critical current density J/sub c/= 10/sup 4/A/cm/sup 2/at 4.2K was measured at 19.7 tesla. Further additions of Ti were made using Sn-xwt%Ti cores furnished by M. Suenaga of Brookhaven National Laboratory. Values of J/sub c/(4.2K) = 10/sup 4/A/cm/sup 2/at 21.4 tesla were achieved. These values are larger than those obtained with Cu-45wt%Nb P/M processed wires. The effects of prestrain are compared with unalloyed Nb P/M processing. Higher values of J/sub c/are obtained in strain-free wires and/or at temperatures below 4.2 K. Electron microprobe measurements of the Ti distribution throughout the single core wires are also presented.         A.C. properties of NbN based Josephson junctions    G. Paterno, A. Cucolo, L. Maritato, A. Nigro, A. Saggese and R. Vaglio Summary: High quality NbN-NbO/sub x/-Pb Josephson devices have been fabricated by r.f. diode sputtering. The critical temperatures of the NbN films were as high as 16.8 K. The junction geometry was defined by photolithography and the oxide barrier was obtained by thermal oxidation or by a plasma oxidation technique. Very low leakage currents have been obtained, corresponding to values of the parameter Vm = 80 mV (Vm = I/sub o/ X 2 mV/I (2mV)). The junction microwave quality factor Q and other a.c. properties have been measured in the frequency range 20 - 300 GHz by looking at the devices self-resonant modes. Q values up to 120 at 4.2 K have been found in the low frequency range, indicating potential performances of these devices for microwave applications such as Josephson voltage standards. Theoretical analysis of the results shows that the main contribution to the losses is related to the NbN films surface impedance.         Niobium nitride based Josephson junctions with unoxidized silicon barriers    E. Cukauskas and W. Carter Summary: NbN based tunnel junctions with unoxidized amorphous silicon barriers and niobium counter electrodes have been investigated under various barrier preparation conditions. The barrier consists of Si:H sandwiched between two thin silicon passivation layers. The H/sub 2/concentration of the sputtering gas was varied form zero to 75% and correlated with barrier height. V/sub m/values at 2mV and 4.2K exceeding 50 mV for some junctions have been obtained. The effective barrier thickness and average barrier height have been varied and are correlated with current density. Junctions with critical current densities exceeding 10/sup 4/Amps/cm/sup 2/have been fabricated. At 10/sup 3/Amps/cm/sup 2/V/sub m/values exceeding 40 mV have been measured. The high voltage I-V characteristics of some junctions have been analyzed using the Simmons model which gives an average barrier height exceeding 160 mV. Some junctions have been fabricated with sum gap voltages exceeding 4.1 mV using various electrode passivation techniques.         Processing of all-NbN tunnel junction series arrays    R. Blaugher, J. Przybysz, J. Talvacchio and J. Buttyan Summary: The processing of an all-NbN tunnel junction with an aluminum oxide barrier system is reported. A NbN/Al/sub 2/O/sub 3//NbN trilayer was deposited by dc magnetron sputtering with the oxide barrier formed by ion beam oxidation. Individual junctions and series arrays were patterned using reactive ion etching and conventional photolithography, 100 junction (10 X 10 /spl mu/m/sup 2/) series arrays have been demonstrated with good tunneling Characteristics showing low leakage (V/sup m/> 20) and acceptable currest densities.         Fabrication and properties of 1 /spl mu/m/sup 2/edge junctions    A. Tugwell, C. Pegrum, G. Donaldson and M. Wicks Summary: We describe the construction and characteristics of Nb/Nb/sub 2/O/sub 2//Pb In edge junctions which are intended primarily for use in DC SQUIDs. Our aim has been to make junctions as small as possible whilst using conventional optical lithography and lift-off techniques. The base electrode for these junctions is an anodised layer of Nb, which is patterned by reactive ion etching to produce angled edges on which the junctions are formed. The tunnel barriers are grown by RF plasma oxidation using 5% O/sub 2/in Ar. A series of test junctions with areas between 1 and 10 /spl mu/m/sup 2/has been made to establish the necessary oxidation conditions, which have been found to be markedly different from those needed for the formation of barriers for window junctions. To measure the junction capacitance, we have made small unshunted SQUIDs with self inductances ranging between 3 and 10pH, and from the effect of resonances on their current-voltage (I-V) characteristics and their periodic response to current injected through the structure, we determine the junction capacitance to be 0.22/spl plusmn/0.01pF/spl mu/m/sup -2/, at a critical current density of 15x10/sup 3/Acm/sup -2/We have incorporated similar junctions in simple magnetometer-style SQUIDs of InH inductance, and for these we measure the flux noise as 8x10/sup -6//spl phi//sub o/Hz/sup -1/2/in the white noise region. These junctions will also be used in more complex SQUIDs which have spiral input coils, and, based on present measurements, we expect these to have a current sensitivity of less than 0.2pAHz/sup -1/2/.         Josephson junctions with silicon interlayer and arrays    L. Amatuni, V. Gubankov, S. Kovtonyuk, V. Koshelets, G. Ovsyannikov, I. Serpuchenko and A. Vystavkin Summary: Dc and microwave properties of the Josephson sandwiches with amorphous silicon interlayer based on refractory materials have been investigated in a wide temperature range. The junctions have nonhysteresis I-V curves down to temperatures 2.2K. Reduced normal state resistance value can be varied in the range R/sub n/S = (5-5000) /spl Omega/ /spl mu/m/sup 2/by changing the Si interlayer thickness; the I/sub c/R/sub n/products V/sub o/= (0.3-1) mV at the same time. Experimental data can be explained by resonance mechanism of electrical charge transferring through silicon interlayer. The transfer takes place along impurity resonant trajectories caused by the presence of the localized states in the forbidden band of the amorphous silicon. The mutual locking in the arrays has been investigated providing that there is a loop for ac Josephson currents. Due to a high V/sub o/value the mutual locking in the two junctions cell has been observed up to the voltage 1 mV which corresponds to submillimeter wavelength.         Refractory material SIS junction structures    V. Belitsky, V. Gubankov, V. Koshelets, G. Ovsyannikov, I. Serpuchenko, S. Shitov, M. Tarasov and A. Vystavkin Summary: Niobium based SIS junction structures for microwave receiving devices were investigated. The possibility of the mixing efficiency improving for Nb-Al/sub 2/O/sub 3/-Nb junctions with a negative resistance on I-V curve near the gap voltage has been demonstrated. Comparative microwave investigation of the parallel and series DC biased arrays shows the advantage of the first one. SIS junction capacitance has been compensated with microstrip or lumped elements at the signal frequency. Such compensated structures were investigated at frequencies 38 and 76 GHz both in waveguide and quasioptic systems.         High quality Ta/PbBi tunnel junctions for 85-110 GHz SIS mixer experiments    G.-J. Cui, D. Face, E. Track, D. Prober, A. Raisanen, D. Crete and P. Richards Summary: We report on the fabrication of small area (1-6 /spl mu/m/sup 2/), high critical current density (10/sup 3/-10/sup 4/A/cm/sup 2/) Ta/Ta oxide/ Pb/sub 0.9/Bi/sub 0.1/SIS tunnel junctions and six junction series arrays designed for use as broadband SIS quasiparticle mixers as 85-110 GHz. These junctions have small subgap leakage currents (1 to 5%), and a "sharp" current rise of width /spl utri/V /spl sim/30-50 /spl mu/V at the sum gap voltage. An RF filter is fabricated on the substrate along with the junctions. The impedance of this filter combined with the junction capacitance is designed to provide a broadband RF match to the mixer over the entire frequency range. A sliding backshort is the only mechanical tuning element. The single junctions as well as arrays are fabricated with a window geometry on fused quartz substrates. The fused quartz substrates require the deposition of a thin amorphous Ge layer which is conducting as room temperature to avoid charging effects during the ion-beam processing steps. Preliminary measurements at 85- 100 GHz show a relatively low gain (-6.9 dB) compared to the performance expected for junctions of this quality. Model calculations suggest that the low gain arises from errors in the implementation of the RF filter design; this can be improved in future work.         Voltage induced variations of the tunnel barrier in Nb/Pb junctions    F. Celani, A. Saggese, S. Pace and G. Rubino Summary: It has been recently shown that, in Nb/Pb junctions having the tunnel barriers grown by r.f. plasma oxidation, large bias voltages induce at room temperature permanent but reversible changes of the I-V characteristics and in particular changes of the Rnn values. In this paper similar variations of thermally oxidated junctions are reported, and a more simple behaviour has been found. Different IV characteristics, corresponding to different values of Run, have been drawn at 77 K on both r.f. and thermal junctions. The voltage dependences of both the conductance and its logarithmic derivative have been studied. A preliminary evaluation of the induced variations of the tunnel barrier parameters is also performed.         Light-sensitive planar interferometers    C. Camerlingo, M. Janawadkar, M. Russo and G. Paterno Summary: Results concerning light-sensitive planar interferometer fabricated by different techniques are reported. A procedure based on the niobium technology is proposed to fabricate a new kind of light-sensitive interferometer. Experimental threshold curves are compared with theoretical behaviors computed in the framework of available theories in both the conditions LI/sub j/ << /spl Phi/sub o/ and LI/sub j/ /spl ges/ /spl Phi/sub o/. A satisfactory agreement has been achieved.         Optimization of circuit parameters for the vortex flow transistor    D. McGinnis, J. Nordman and J. Beyer Summary: The Vortex Flow Transistor (VFT) has been proposed as a superconducting amplifying device. Useful circuits at microwave frequencies may be achievable using distributed amplifier concepts. However, realization of these circuits depends on obtaining a circuit model for this device and then characterizing and optimizing the elements that make up this model. In order to study these elements, a group of devices with various geometric differences were fabricated with Nb-Pb technology. Initial results of a study of the low and high frequency properties of the transresistance, output resistance, feedthrough capacitance, and input inductance of the VFT are presented.         Semiconductor heterostructure weak links for Josephson and superconducting FET applications    A. Kleinsasser, T. Jackson, G. Pettit, H. Schmid, J. Woodall and D. Kern Summary: Superconductor-normal-superconductor (SNS) weak links using a semiconductor as the normal region are of interest for applications in high frequency Josephson devices and in superconducting field effect transistors. Recently, there has been a revival of interest in materials such as InAs which, in principle, allow true SNS structures without tunneling (Schottky) barriers at the electrodes, In this paper we discuss the requirements for semiconductor SNS Josephson and FET devices and describe the fabrication and characterization of planar SNS weak links in which the normal region is InAs, which is part of a heterostructure consisting of a thin (100 nm) layer of n-InAs grown on undoped GaAs. Nb electrodes defined by electron beam lithography have been made with spacings as small as 260 nm. Preliminary measurements indicate that the devices have good electrical behavior which is well explained by SNS weak link theory, using coherence lengths calculated from measured material parameters. These weak links can be the basis for superconducting FET devices, and have the significant advantage of allowing simple device isolation compared with bulk InAs, which was used in earlier work.         Field effect and Josephson junctions    V. Kresin Summary: The value of the Josephson current in an S-MS system, where M contains low-dimensional electron gas, can be affected noticeably by an applied voltage (field effect). This effect is directly related to the possibility of building a three-terminal device. The dependence of the current on the carrier concentration is studied. The peculiar situation When the state of lowest subband is described by the "dirty" limit whereas the higher subband represent the "clean" limit appears to be realistic. Inter-subband scattering results in a non-monotonic behavior of the current.         A three terminal Josephson junction with a semiconducting two-dimensional electron gas layer    Z. Ivanov and T. Claeson Summary: We have performed simple model calculations of a three terminal, voltage regulated superconducting device. It consists of superconducting source and drain electrodes separated by a controlled weak superconducting link, i.e. a semiconductor where the charge carrier concentration can be varied by a gate voltage. The gate is separated from the semiconductor by a thin insulator and a two-dimensional electron gas (2DEG) can be induced at the semiconductor surface in the case of strong inversion. The 2DEG transport properties determine the supercurrent flow between the electrodes. The device I-V characteristics have been calculated for several gate voltages using parameters typical for SiO/sub 2//p-InSb and AlGaAs/p-GaAs junctions.         NbN/BN granular films--A novel broadband bolometric detector for pulsed far infrared radiation    M. Leung, U. Strom, J. Culbertson, J. Claassen, S. Wolf and R. Simon Summary: Thin films of NbN/BN are investigated as photodetectors for pulsed, far infrared radiation. It is found that there are two distinct modes of operation for these devices, depending on whether the device is biased in the superconducting or resistive regime. When the device is biased into the resistive region, the absorption of photons decreases its resistance. Conversely, when the device is superconducting, the absorption of photons causes the resistance to increase. The more sensitive mode occurs when the device is biased superconducting. Detector parameters are studied in this condition and are compared to other, more conventional detectors (ie. pyroelectric, point contact diodes, semiconductor photoconductors). It is found that the NbN/BN thin film detectors have response times faster than 1 ns, and sensitivities of about 0.2 V/W.         Detecting "missing mass" candidates with the superheated superconducting detector    A. Drukier, K. Freese and D. Spergel Summary: Evidence from astrophysics and particle physics suggest that weakly interacting massive particles(WIMPs) may comprise most of the mass of the galaxy. If these particles exist, they can be detected by cryogenic detectors. The superheated superconducting colloid detector is well suited for use in the search for WIMPs. The earth's motion around the Sun provides a distinctive signal which can be used to confirm a detection.         Tests of superheated superconducting colloids using an RF SQUID    M. Le Gros, A. Kotlicki, B. Turrell and A. Drukier Summary: We report two tests designed to study the practicality of a superheated superconducting colloid detector using a SQUID read-out system. In the first test, the individual 'flips' of ten 15 /spl mu/m radius tin grains were observed as the temperature was swept through the superheated superconducting-normal phase transition. In the second test, we were able to observe transitions induced by 90 keV /spl gamma/-rays in a colloid of 5/spl mu/mm radius grains in epoxy.         Josephson analog amplifier with large current gain    K. Yoshida, T. Hashimoto, T. Nagatsuma and K. Enpuku Summary: Analog amplifiers utilizing the flux-flow phenomenon in a long Josephson tunnel junction, Flux-Flow Amplifier(FFA), have been studied experimentally. The operation of the amplifier is based on the modulation of dc I-V curves of a long Josephson junction by applied magnetic fields, which acts as a magnetic-field to voltage transducer. Strong dependences of the transducer characteristics on junction parameters and geometries are elucidated. Experiments on a series array of FFA's for higher current gains and larger output voltages were also carried out successfully.         Transport properties of a superconductor-semiconductor ohmic contact    A. Davidson, M. Brady, D. Frank, J. Woodall and A. Kleinsasser Summary: We report electrical measurements of a sandwich structure consisting of a niobium electrode in contact with a thin lightly doped n type InGaAs layer. The Bottom of the sandwich is a degenerate layer of n-type InGaAs used to collect the current. The semiconductor layers are grown by molecular beam epitaxy (MBE). These three layers are the essence of the proposed superconducting-base, semiconductor-isolated transistor (SUBSIT), lacking only the emitter tunnel junction. It could also form the basis for a superconducting FET type device. We have observed a resistance rise, beginning just below the transition temperature of the niobium, and continuing to at least 2 K. Nonlinear IV curves are also measured, and may be interpreted in some instances as space charge limited current flow.         Microscopic simulation model of Josephson junctions for standard circuit analysis programs    H. Kratz and W. Jutzi Summary: A microscopic simulation model is formulated with the convenient notation of standard circuit analysis programs for digital computers, such as SCEPTRE, ASTAP, etc. The complex Josephson and quasiparticle currents with finite slopes at the gap are approximated with two networks with up to 8 lumped elements each. The microscopic simulation model yields considerably more reliable results than a refined RCSJ-model on the expense of an 30 % longer computation time.         Josephson junction A/D converters using differential coding    S. Rylov, V. Semenov and K. Likharev Summary: We propose a new type of the Josephson junction A/D converter which allows one to increase the conversion accuracy (characterized by the output bit number N) without using high-precision (/spl delta/spl lambda///spl lambda/ /spl sime/2/sup -N/) components. This improvement is possible due to a specific structure of the new device including a fast low-bit (p << N) input A/D converter and several digital differentiation/integration stages. We discuss general properties of this device and possible realization of its main components in the Josephson technology. Estimates show that at relatively low signal frequencies an additional digital stage (1f filter) can improve drastically the converter performance making it considerably more accurate than any other A/D converter proposed earlier.         Josephson 4-bit digital counter circuit made by Nb/Al-oxide/Nb junctions    H. Nakagawa, I. Kurosawa, S. Takada and H. Hayakawa Summary: A new Josephson 4-bit digital counter circuit has been demonstrated. Direct-coupled data-latch units which consists of a four-junction logic(4JL) gate family are utilized to make a flip-flop circuit for counting. The counter is designed to be driven by a two-phase mono-polar power supply. The counter circuit has been fabricated using 3/spl mu/m-Nb/Al-oxide/Nb junction process. The counter has three operating modes of counting, data-loading and clearing which can be adapted to Josephson digital logic system. Experimental tests have been carried out successfully for these operating modes. Computer simulations indicate that the 4-bit counter operates in 315ps.         A content addressable memory circuit using Josephson junctions    M. Morisue, M. Kaneko and H. Hosoya Summary: This paper describes a content addressable memory circuit using Josephson NDRO memory cells, in which a novel Josephson multi-response resolver is included. The memory circuit proposed here performs the searching functions such as coincidence, incoincidence and don't-care function, in addition to the conventional memory function of writing and reading. In order to investigate how a high performance operation can be achieved, computer simulations have been made. Simulation results show that the cycle time of memory operation is 60psec, power dissipation is 0.28/spl mu/W/cell and the cycle time of multi-response resolver operation is 153psec.         A Josephson associative memory circuit    M. Morisue, H. Shimizu and H. Fukuzawa Summary: This paper proposes a novel associative memory circuit using Josephson interferometers. This associative memory circuit is mainly constructed with the nondestructive memory cell in which a self-rewriting operation can be achieved by setting a coil between the terminals of the interferometer. The principle of the associative memory circuit is described and the results of simulation for the operation are illustrated. The results show that the cycle time of operation is less than 75ps and the design tolerance of input signals for the memory circuit is about 8%.         High-speed measurements of single gates; Higher-voltage gates    H. Ko, D. Petersen and T. Van Duzer Summary: The gate delay of a single CIL AND gate is measured with a Josephson sampler. The CIL gate consists of a CIL interferometer preceded by a three-junction SQUID isolation stage. The smallest delay observed was 6 ps. Simulation results and sampling measurements of a gate designed to switch to 3V/sub g/are also reported. Processing variations precluded successful operation of the higher-voltage gate. The simulations suggest that this failure is due to the large difference of the average critical current from the design value. Scaling arguments show that for small-scale circuits high-speed operation with gate delays of a few picoseconds can be achieved with junction dimensions approximately equal to the Josephson penetration depth.         Experimental realization of a resistive single flux quantum logic circuit    V. Koshelets, K. Likharev, V. Migulin, O. Mukhanov, G. Ovsyannikov, V. Semenov, I. Serpuchenko and A. Vystavkin Summary: An integrated circuit including all basic components of the recently suggested Resistive Single Flux Quantum (RSFQ) logic family has been designed, fabricated and tested successfully. The circuit includes a generator of periodic SFQ pulses, four buffer/amplifier stages for splitting, channeling and regeneration of the pulses, a detector/load stage, and universal RSFQ logic gate (here performing the NOT function). The 10/spl mu/m design rule circuit employs 13 active Nb - Al/sub 2/O/sub 3/- Nb Josephson junctions with the critical current density /spl sim/ 0.5 kA/cm/sup 2/. externally shunted by Mo resistors with R 1 Ohm. The shunting provided critical damping of the junctions (/spl beta//sub c//spl lsim/ 1) and reasonable (/spl sim/ 500 /spl mu/V) I/sub c/R product. The circuit operation has been tested by measurement of dc voltages\bar{V}_{i}across various Josephson junctions as functions of the dc current through the pulse generator. Correct and stable operation of the circuit for the clock frequencies from 0 to /spl sim/30 GHz has been demonstrated.         Ultimate performance of the RSFQ logic circuits    O. Mukhanov, V. Semenov and K. Likharev Summary: A new family of dc-powered Josephson junction digital devices, the Rapid Single Flux Quantum (RSFQ) logic, is described. The devices use overdamped Josephson junctions and two-junction interferometers to store, pass and process the digital information presented in form of single flux quanta. We have carried out extensive numerical simulation of the dynamics of the RSFQ logic gates and of some more complex circuits including serial full adder and reversible shift register, within the standard microscopic-theory ("Werthamer") description of Josephson junctions. The minimum clock cycles of the basic RSFQ circuits turn out to be as small as 2.5 ps. The most promising ways to use the RSFQ logic circuits at the present stage of development of the Josephson junction digital technology are discussed.         Specific problems of numerical analysis of the Josephson junction circuits    A. Odintsov, V. Semenov and A. Zorin Summary: We describe solutions of two specific problems of numerical simulation of the Josephson junction circuits (these problems are not typical for the semiconductor electronics and thus had presumably not been considered in the designing of earlier CAD systems). The first one is modelling of circuits comprising many Josephson tunnel junctions within the framework of the microscopic ("Werthamer") theory resulting in nonlinear integro-differential relation between the junction current and voltage. Using a novel finite-difference scheme, an unexpected simple solution of this problem has been found. As a result, the computer time and memory necessary for the modelling are only three to five times larger than those for the similar analysis within the simplest RSJ model. The second problem is the optimum averaging of variables, necessary to filter out the Josephson and other high-frequency oscillations. We have solved this problem using ideas from the theory of digital time-dependent filters. The algorithms based on these methods are incorporated into our CAD program COMPASS which is extensively used for analysis of various analog and digital devices based on the Josephson effect.         Response of a Josephson junction to a stepped voltage pulse    D. Dykaar, R. Sobolewski, T. Hsiang and G. Mourou Summary: We have developed a fully cryogenic electro-optic sampler by integrating and immersing in superfluid helium both the photoconductive switch and the birefringent lithium tantalate sensor. The ultimate temporal response of the system as determined by measuring the transient onset of photoconductivity in a GaAs switch was less than 400 fs. The system was arranged into a coplanar transmission line geometry and used to probe the switching of a 30 X 30 /spl mu/m/sup 2/Josephson tunnel junction. Both time-dependent waveforms of the transmitted signal and current-voltage characteristics of the junction switched by a picosecond input pulse were measured. The results were compared to transient simulations based on the resistively and capacitively shunted junction model, and showed that: the initial junction response was limited only by the time integral of the input pulse, the switched voltage was proportional to the total charge delivered by the pulse, and there was no turn-on delay time. This represents the first, in situ measurement of the response of an unbiased Josephson tunnel junction to a stepped, picosecond pulse.         Reverse switching current distributions in underdamped Josephson junctions    R. Cristiano and P. Silvestrini Summary: The probability of the reverse switching currents I/sub r/from the finite voltage to the Josephson current state are reported. The results are based on a more general analysis recently developed. The work is relevant in the region of current near the deterministic value I/sub r/of the reverse current where noise effects are more relevant. The probability distributions are reported for various values of the junction, noise and bias parameters. A comparison with the distributions of the Josephson critical current is also reported in order to discuss some aspects of the switching dynamics of the junction.         A fast open-cycle cryocooler for cryogenic high-speed signal processing circuits    G. Hohenwarter, J. Grange and S. Whiteley Summary: The design of a liquid helium based open-cycle cryocooler for small scale integrated Josephson junction circuits is described. In addition to low, medium and high speed transmission line access to the circuits, the cooler features a rapid startup time and low liquid consumption. The system makes use of materials and circuits manufactured on substrates with low thermal conductivity cooled by counterflow heat exchange between the working medium and the influx of heat.         Josephson data latch for frequency agile shift registers    J. Przybysz and R. Blaugher Summary: A Josephson data latch was designed and simulated with the SPICE program. The data latches were connected in series to form a shift register which showed frequency agile operation. The novel latches were based on Direct Coupled Logic OR gates to obtain high speed performance. Latches were triggered by the rising edge of the clock voltage to provide a sampling interval. Switching of the triggering junction to the resistive state deactivated the latch's input response which prevented racing of the two phase logic. Simulations showed proper operation of the shift register at frequencies up to 15 GHz. The wide operating margins of the circuit are suited to LSI fabrication. Comparison of the model junction to currently available Josephson technology indicated that real chips should be capable of frequency agile operation in the multigigahertz range.         Resonance interaction between fluxon and plasma waves in long Josephson junction    A. Golubov and A. Ustinov Summary: The first zero-field step (ZFS1) on the current-voltage characteristic (CVC) of the long overlap Josephson junction with periodically modulated critical current density (CCD) distribution has been investigated analytically and numerically within the framework of perturbed sine-Gordon equation. A set of peaks on ZFS1 has been observed at fixed voltages dependent on the spatial period of CCD distribution. These peaks have been shown to be due to the resonance interaction of a soliton and plasma waves in the junction provided the following condition holds: mW/sub sol/= W/sub p/, where m is an integer.         Influence of single trapped Abricosov's vortices on the properties of Josephson tunnel junctions    A. Golubov and M. Kupriyanov Summary: The critical and quasiparticle currents through Josephson tunnel junction are calculated on the basis of the microscopic approach in the case of weak external magnetic field (H << H/sub C2/) trapping in the form of single vortices. The following situations are considered: 1) single vortex localized in one electrode; 2) one or a number of pairs of misaligned vortices localized in both electrodes with their locations depending on the value and spatial distribution of pinning forces in superconducting films. In both cases quasiparticle current depends only on the densities of states in the vortex cores and is numerically calculated in the whole temperature range 0 < T < T/sub c/. For all values of T thers are pronounced peaks on dI/sub q//dV curves at voltage V=/spl utri//e. In contrast the critical current is influenced mainly by magnetic field distribution in the junction area. The suppression of total critical current is evaluated for various vortex configurations in the junction.         Wide margin voltage locked array of Josephson junctions and its use as amplifier    M. Gershenson Summary: The use of unshunted junctions to close the superconducting loop of two shunted junctions in series is shown to improve the voltage locking range compared to the more common use of passive elements such as resistors or capacitors. Stacking pairs of junctions in a ladder-like form with one junction common for each two steps makes it possible to phase lock more than two junctions. Simulations show that four junctions with 5% matching can be locked from 0 to 55/spl mu/V. The device can also be used as a voltage amplifier by driving one of the junctions. Simulations show that an array of four series junctions operates as an amplifier between 12/spl mu/V to 33/spl mu/V input. Input impendance was 6 ohms and output impedance was 12 ohms.         Superconductive delay line with integral MOSFET taps    M. Delaney, R. Withers, A. Anderson, J. Green and R. Mountain Summary: A superconducting tapped delay line with programmable MOS transistors for tap weights has been designed, fabricated, and tested. The device operates between 2 and 5 GHz at 4.2 K. The silicon substrate of the integrated semiconductor-superconductor device is used both as the semiconductor material for MOS processing and as the dielectric for the microstrip delay line. The superconducting material is niobium, which is processed after the semiconductor fabrication because the superconducting properties of niobium can degrade if exposed to high temperatures. Both aluminum and niobium are used for transistor gates and interconnects. The novel niobium-gate transistors worked as well as the aluminum-gate transistors at 4.2 K with channel mobilities 3 to 5 times higher than at room temperature. Test results on the weighted tapped delay line show that the amplitude of the tapped outputs may be varied linearly over an 18-dB range between 2 and 2.4 GHz by gate-voltage modulation of the MOSFET channel conductance.         Microstrip resonances in superconducting circuits    A. Smith, B. Dalrymple, A. Silver, R. Simon and J. Burch Summary: Josephson junctions connected to high Q microstriplines display current-steps which we attribute to standing wave resonances. The step voltages of the resonances depend on sample geometry and correspond to frequencies at which the loaded microstrip is resonant. The voltages of the resonances are insensitive to applied magnetic field and junction current density. Current step amplitudes scale with the zero-voltage critical current, and are largest for zero applied magnetic field. The strength of these resonant steps has important implications for biasing weakly damped Josephson junction circuits. In addition, the resonances are a useful tool for measuring microstrip properties.         The large coil task and results of testing U.S. coils    P. Haubenreich Summary: The United States, EURATOM, Japan, and Switzerland have collaborated since 1978 in development of superconducting toroidal field coils for fusion reactor applications. The United States provided a test facility and three coils; the other participants, one coil each. All coils have the same interface dimensions and performance requirements (stable at 8 T), but internal design was decided by each team. Two U.S. coil teams chose bath-cooled NbTi, 10-kA conductors. One developed a Nb/sub 3/Sn conductor, cooled by internal flow, rated at 18 kA. All U.S. coils have diagnostic instrumentation and imbedded heaters that enable stability tests and simulated nuclear heating experiments. In single-coil tests, each coil operated at full current in self-field (6.4 T). In six-coil tests that began in July 1986, one U.S. coil and the Japanese coil have been successfully operated at full current at 8 T. The other coils have operated as background coils while awaiting their turn as test coil. Coil tests have been informative and results gratifying. The facility has capably supported coil testing and its operation has provided information that will be useful in designing future fusion systems. Coil capabilities beyond nominal design points will be determined.         The Japanese LCT coil    S. Shimamoto Summary: The Large Coil Task (LCT) is providing all of the participants with new experiences through international hardware collaboration. The objectives of LCT are both to demonstrate an 8 T field in a large toroidal configuration and to compare performance features of 6 different coils. Almost ten years has passed for this work since the beginning. Design, verification testing, and fabrication evolved in parallel with construction of test facilities which required as much advanced technology as the coils themselves. Now the project is at the final stage and is providing experimental data on the performance of the six large superconducting coils. The paper is prepared for the round table discussion and describes the design parameters, domestic test results, and full torus test results of the Japanese LCT coil.         The Euratom-LCT coil    A. Ulbricht Summary: A review of the design, construction, and operation of the EURATOM LCT coil as a contribution to the International Energy Agency (IEA) experiment, "The Large Coil Task," is presented. The test results obtained in the TOSKA facility at the Nuclear Research Center, Karlsruhe and in the International Fusion Superconducting Magnet Test Facility (IFSMTF) at Oak Ridge are summarized.         Design and testing results of the swiss LCT coil    J. Zichy and G. Vecsey Summary: The Swiss contribution to the Large Coil Task at Oak Ridge National Laboratory in Tennessee, U.S.A. is a D-shaped 2.5- X 3.5-m/sup 2/bore, superconducting toroidal field coil of 8-T field using forced-flow-cooled filamentary NbTi conductor. Switzerland joined this international collaboration in September 1978 and the coil arrived at the International Fusion Superconducting Magnet Test Facility on February 2, 1984. In the summer of the same year the coil was successfully cooled down. The first opportunity to energize the Swiss coil arose in spring 1986 during the ongoing six-coil test. This paper presents the main principles guiding the design, describes the related theoretical calculations, and the supporting experimental program. It discusses the fabrication experience and summarizes the test results obtained to date.         T-15 facility and tests    N. Chernoplekov and N. Monoszon Summary: This paper describes, mainly, the I.V. Kurchatov Institute of Atomic Energy (IAE) test facility for a large-scale superconducting (SC) magnet and test results of the T-15 toroidal field (TP) Nb/sub 3/Sn coils. The results of hydraulic, thermophysical and electrical tests of full-scale experimental coils under the conditions close to the operating ones in the TF magnet have confirmed the correctness of the main design solutions and allowed one to start the production of the working coils. Technological tests of the working coils preceding their installation in the T-15 magnet have been started.         Microstructure, resistivity and the anisotropy of the upper critical field in NbN thin films    D. Rudman, J. Juang, R. van Dover, S. Nakahara, D. Capone II and J. Talvacchio Summary: The upper critical field of most polycrystalline NbN thin films is anisotropic. with the perpendicular critical field H/sub c2/(/spl perp/) larger than the parallel critical field-H/sub c2/(/spl par/). We have measured the angular dependence H/sub c2/(/spl theta/) for samples with both a columnar and non-columnar microstructure. In both cases we find a rounded maximum near H/sub c2/(/spl perp/). The shape of H/sub c2/(/spl theta/), combined with the known microstructure of the films and the linear temperature dependence of H/sub c2/for both field orientations leads us to conclude that the mechanism responsible for this anisotropy is an anisotropic conductivity in the film, probably due to differences in the grain boundary resistance in the plane of the film and normal to the film. In contrast, a single crystal film shows only surface superconductivity.         Ion-beam deposition of NbN/sub x/C/sub y/thin films for microelectronic applications    L.-J. Lin and D. Prober Summary: We have fabricated high quality superconducting NbN/sub x/C/sub y/thin films using a low-energy dual ion-beam fabrication method. In this method, one ion beam sputters Nb to the substrate while the second beam bombards the growing film with low energy (/spl sim/100 eV) N/sub 2/+CH/sub 4/ions. The use of methane as a source of carbon is essential for this method. NbN/sub x/C/sub y/thin films fabricated in this way have T/sub c/up to 13.2K, resistivit /spl sim/80-120 /spl mu/spl Omega/cm, residual resistance ratio /spl sim/1.0 and calculated magnetic penetration depths <285 nm. These films are deposited on Si wafers which are not intentionally heated or cooled. Electronic tunneling studies indicate that these films are strong coupled superconductors (2/spl Delta//kT/sub c//spl les/ 4.0) with superconducting energy gaps up to 2.43 meV. NbN/sub x/C/sub y//native oxide/Pb-alloy Junctions have properties suitable for SIS mixer applications.         NbN film deposition using optical emission spectroscopy    M. Bhushan Summary: NbN films were deposited on unheated Si substrates by dc and rf reactive planar magnetron sputtering of Nb in an Ar and N/sub 2/gas mixture. The optical emission spectrum of the plasma was recorded for different sputtering conditions and the target sputtering rate was found to be proportional to the intensity of any Nb emission line. A model for the reactive sputtering mechanism was developed and the optimum sputtering parameters were selected by observing the change in the Nb emission line intensity as a function of the partial pressure of nitrogen. The critical temperatures of the films were in the 13 to 15.8 K range.         Thermal annealing of RF sputtered NbN    W. Carter and E. Cukauskas Summary: The effects of thermal annealing on RF sputtered NbCN films and completed NbN-based tunnel junctions has been investigated. The starting films were RF sputtered at temperatures from 150/spl deg/C to 650/spl deg/;. After a vacuum anneal at 600/spl deg/C for six hours the transition temperature reached a maximum of 14.6K and depended only on the carbon concentration, for those films deposited at 200/spl deg/C and 400/spl deg/C. Vacuum annealing for one hour at temperatures of 900/spl deg/C or more caused the formation of additional phases. Rapid thermal annealing, RTA, at temperatures from 600/spl deg/C to 1200/spl deg/C for times from one to 100 sec resulted in increased T/sub c/with increased annealing temperature. The maximum T/sub c/produced by RTA was 16.6K. The lattice parameter of annealed /spl delta/ -phase NbCN was decreased toward the accepted value of 4.41 /spl Aring/. Resistivity of the annealed films decreased except when the films cracked during annealing. RTA for 10 sec at 750/spl deg/C of a completed NbN/Si/NbN edge junction increased the electrode gaps but for NbN/Si/Nb planar junctions the sum gap decreased. Microshorts also appeared in both types of junctions after annealing.         Microwave surface resistance of reactively sputtered NbN thin films    J. Bautista, D. Strayer, M. Berry and S. Faris Summary: The surface resistance of niobium nitride (NbN) thin films has been measured at 7.78 and 10.14 GHz in the temperature range of 1.5 to 4.2 K. The films were reactively sputtered on sapphire substrates to a thickness of approximately one micron. The surface resistance was determined by measuring the quality factor (Q) of the TEO11 mode of a lead-plated copper cavity where the NbN served as one end-cap of the cavity.         RF sputter-deposited aluminum-oxide films as high quality artificial tunnel barriers    J. Barner and S. Ruggiero Summary: We report on the results of fabricating artificial tunnel barriers by the simple method of direct sputtering of an aluminum-oxide (Al/sub 2/O/sub 3/) target. These barriers have been studied by preparing tunnel junctions of the form: Cu/AlOx/C.E., with aluminum-oxide layers ranging in thickness from 8 to 20 /spl Aring/ and counter-electrodes (C.E.) of Cu, Pb and PbBi. We have found that barriers with exceptionally large effective barrier heights, in excess of 2eV, and low zero-bias conduction, less than 0.4% leakage, can be reliably obtained by this method. We discuss the fabrication of these barriers and the systematics of both the effective (WKB) barrier shape, and superconducting and normal-state tunneling characteristics as a function of the measured barrier film thickness. X-ray photoelectron spectroscopy (XPS) studies on sputter-deposited aluminum-oxide films indicate the single composition, namely Al/sub 2/O/sub 3/. This method should prove universally applicable for depositing very high quality tunnel barriers.         Tunnel junctions fabricated from coherent NbN/MgO/NbN and NbN/Al/sub 2/O/sub 3//NbN structures    J. Talvacchio and A. Braginski Summary: Trilayer structures consisting of two layers of epitaxial, single-crystal NbN and an intervening 2-nm-thick layer of epitaxial MgO or Al/sub 2/O/sub 3/, have been formed in four or two, respectively, crystallographic orientations. The NbN films were deposited by dc magnetron sputtering and oxide films were grown by dc sputtering or evaporation. Single-crystal NbN films did not have significantly higher superconducting transition temperatures or significantly lower normal-state resistivities than films grown by polycrystalline epitaxy. However, the use of single-crystal epitaxy to deposit tunnel barriers provided new experimental parameters for control of thickness uniformity that affect the tendency of an epitaxial layer to grow as a 2-D or 3-D film. One of these experimental parameters, increasing the barrier deposition temperature, was shown to decrease the junction subgap conductance and to increase the effective barrier height for epitaxial barriers, but was detrimental to polycrystalline junctions.         All refractory NbN/MgO/NbN tunnel junctions    H. LeDuc, J. Stern, S. Thakoor and S. Khanna Summary: We report the fabrication of all-refractory superconductor-insulator-superconductor tunnel junctions of the form NbN/MgO/NbN. The MgO insulating barrier was deposited by e-beam evaporation. High quality junctions were fabricated with sum gaps of 5.2 meV, and a small subgap leakage parameter (V/sub m/=30 mV, measured at 3mV). These devices are for eventual use as quasiparticle mixer elements in millimeter/submiltimeter wave heterodyne receivers. Fabrication techniques and current-voltage characteristics are discussed. We also propose a new growth mode for MgO films on NbN.         High-resistance SNS sandwich-type Josephson junctions    A. Barrera and M. Beasley Summary: We have investigated the behavior of SNS and SIS junctions with barriers in the vicinity of the Metal-Insulator (M/I) transition. We use Nb for the superconductor and amorphous-(Nb-Si) for the barrier. All junctions were made by means of electron-beam evaporation on Al/sub 2/O/sub 3/substrates. The junction areas were defined by the Selective Niobium Anodization Process (SNAP). We have made junctions down to 8 X 8 /spl mu/m/sup 2/and barrier thicknesses in range from 250 /spl Aring/ to 600 /spl Aring/. The composition of the barrier was varied from 5 % Nb to 15 % Nb. Working on the metallic side of the M/I transition we observe /spl mu/-bridge-like I-V characteristics with R/sub n/A /spl sim/0.3 /spl Omega/-/spl mu/m/sup 2/and I/sub c/R/sub n//spl sim/200 /spl mu/V.         High-speed unit-cell for Josephson LSI circuits using Nb/AlO/sub x//Nb junctions    S. Kotani, N. Fujimaki, S. Morohashi, S. Ohara, T. Imamura and S. Hasuo Summary: In this paper, we will discuss the design, fabrication and evaluation of an OR gate and a unit-cell for Josephson logic LSI circuits using all niobium junctions. We fabricated the unit-cell using two Modified Variable Threshold Logic (MVTL) OR gates and one single-junction AND gate. The cell performs the logical opration (A+B).(C+D), which is the basic operation of the dual rail logic method, suitable for Josephson devices. The gates utilized Nb/AlO/sub x//Nb Josephson junctions with a minimum diameter of 2.5 /spl mu/m, Nb wirings, Mo resistors, and SiO/sub 2/insulators. The cell size, complete with supply resistors, was 82 /spl mu/m X 132 /spl mu/m. The gate delays were measured using the Josephson sampling technique with two sampling heads. The minimum delay of the OR gate in the cell was 4.2 ps, and that of the three-fanout cell was 11.5 ps. The experimental results were consistent with calculations based on measured parameters.         Abrikosov vortex memory with improved sensitivity and reduced write current levels    K. Miyahara, M. Mukaida, M. Tokumitsu, S. Kubo and K. Hohkawa Summary: Studies are carried out on a nondstructive readout random access memory cell based on the use of Abrikosov vortices in thin-film type-II superconductor with a view to achieve high vortex sensitivity and low current levels. Employing an overhang structure, the magnetic flux of stored vortices is effectively guided to the sense gate (SG) and the saturated shift value is increased several times larger than that of a cell without an overhang structure. It is also experimentally verified that stored vortices accumulate near the entrance edge of vortex storage region (VSR) because of its large pinning force. Utilizing vortex driving current flowing through VSR film, the vortices are driven toward the SG and accumulated in the VSR near the SG. Low write current levels of less than 6 mA are achieved utilizing low pinning force films, such as amorphous Mo films, using a vortex driving current.         A superconducting filter-type powering device (SFPD) for the Josephson computer system    J. Tsai and Y. Wada Summary: To supply a large ac powering current to the low-impedance Josephson computer from the external source, some type of impedance-matching circuit is required. The SFPDs are band-pass filter type superconducting impedance transformers, designed to operate at around 0.5GHz with impedance transfer ratio as large as 16000. The SFPD can potentially be design to operate at much higher frequencies. Its resonant-mode operation results in high current gain and stable duty in the power network. The SFPD for a hypothetical 8K-gate Josephson computer system was designed and fabricated. The capacitors in the circuit consist of Nb electrodes and low-loss Nb/sub 2/O/sub 2/dielectrics. The inductors and the dummy resistors consist of Nb and Mo thin films respectively. For the 3-stage SFPD, the operation at 0.40/spl sim/0.53GHz was confirmed with the current gain of 95 and the VSWR of 5. The 3m/spl Omega/ input impedance of the Josephson system was transferred to 27/spl Omega/.         Series-array Josephson voltage standards    R. Kautz, C. Hamilton and F. Lloyd Summary: Series arrays typically including 1500 Josephson junctions driven at 90 GHz have been used to generate quantized reference voltages in excess of 1 V. Such standards simplify the procedure and reduce the measurement uncertainities in the calibration of electrochemical cells.         Dynamic behavior of a Josephson latching comparator for use in a high-speed analog-to-digital converter    D. Petersen, H. Ko and T. Van Duzer Summary: A Josephson latching comparator for use in an analog-to-digital (A/D) converter has been designed and experimentally investigated. A novel on-chip waveform sampling system is presented; this was used to measure the dynamic behavior of a single comparator circuit. The circuits are fabricated with a modified lead-alloy process. Results obtained using this system are compared with simulations and the two are shown to be in good agreement. An A/D converter is proposed in which an array of comparators is used to-quantize rapidly changing input waveforms. A simple encoding scheme is presented which generates a natural-binary representation of the analog input.         Analog signal correlator using superconductive integrated components    J. Green, L. Smith, A. Anderson, S. Reible and R. Withers Summary: Analog superconductive components have been integrated to form a device capable of cross-correlation between wideband analog input signals. The device contains a tapped niobium delay line, tunnel-junction mixers, a lumped-element L-C resonator, and a tunnel-junction comparator. The tapped delay line is realized by a niobium stripline folded in a meander pattern on a rectangular silicon substrate. An array of Nb/Nb/sub 2/O/sub 2//Pb tunnel junctions acts as a mixer to form the product of delayed samples of two carrier-offset analog signals counterpropagating along the transmission line. The resultant mixer products from the junction arrays are integrated and stored in a high-Q (/spl ap/600) resonator consisting of a lumped-element L-C network, tuned to the offset frequency. The low-leakage capacitor dielectric is formed from electrolytically anodized niobium. A superconductive tunnel junction imbedded in the resonator circuit is operated as a variable-threshold comparator to detect the time-integrated current stored in the resonator. Performance results from such a time-integrating correlator are presented, along with a discussion of the important design issues as they relate to analog signal processing.         A Josephson junction time domain reflectometer with room temperature access    S. Whiteley, G. Hohenwarter and S. Faris Summary: Using a novel chip architecture and cooling method, a superconducting Josephson Junction time domain reflectometer subsystem has been developed which provides wide bandwidth access to the room temperature environment. Presented is an overview of the subsystem, with emphasis on the cryogenic circuitry employed. Results and performance limitations are described.         Kinetic inductance microstrip delay lines    J. Pond, J. Claassen and W. Carter Summary: Microstrip delay lines employing the phenomenon of Kinetic inductance have several potential advantages for analog signal processing. These properties will be discussed and contrasted with other delay line technologies. Several kinetic inductance microstrip delay lines have been fabricated using niobium, niobium nitride and various dielectrics. These devices have been measured with both transient and time harmonic signals. The results of these tests are compared to theoretical predictions and some estimation of expected device performance is made.         A superconducting magnet generating fields over 18 T    K. Tachikawa, K. Inoue, M. Saeki, K. Aihara, T. Fujinaga, H. Hashimoto and R. Saito Summary: A superconducting magnet has been constructed and succeeded in generating a field of 18.1 T by the operation at 4.2 K without any quenching. This field is the new highest record generated by a superconducting magnet so far. The maximum stored energy of the magnet is about 6 MJ. The magnet consists of an outer magnet (I) with a 455 mm bore, an outer magnet (II) with a 180 mm clear bore and an inner magnet with a 30 mm clear bore. The conductor used in the outer magnet (I) is a monolithic multifilamentary Nb-Ti and that used in the outer magnet (II) is a monolithic multifilamentary (Nb,Ti)/sub 3/Sn. The outer magnet (I) and (II) are electrically connected in series to complete an outer magnet which is excited up to 14.2 T at 4.2 K. The inner magnet is an assembly of pancakes made of surface diffusion processed V/sub 3/Ga tapes and insitu processed V/sub 3/Ga tapes, and excited by another DC power supply up to an incremental field of 3.9 T at 4.2 K in the back-up field of the outer magnet. The high stability of the outer magnet makes the operation of duplex superconducting magnet system convenient and safe. We are planning to generate fields above 20 T by the operation of this magnet system at 1.8 K.         Fabrication of a high current Nb/sub 3/Sn forced flow conductor for the 12 tesla SULTAN test facility    B. Jakob and G. Pasztor Summary: For the Swiss insert coil of the 12 T SULTAN Test Facility, a Nb/sub 3/Sn forced flow conductor, designed for an operating current of 6 kA at 12.2 T and 5 K, has been fabricated. To develop the manufacturing techniques, a 20 m full size prototype conductor was first produced in laboratory conditions at SIN. Based on the experience gained with the prototype, a new production facility devoted to the components joining was designed and built. At the same time, work got under way to manufacture the three-stage flat cable and to react it to form the Nb/sub 3/Sn. After a brief description of the superconducting cable production, the fabrication of the 870 m long conductor in the new production facility will be discussed. A detailed description of the facility consisting of two fabrication lines is given, and the production experience is presented.         A rapid, semiempirical method of calculating the stability margins of superconductors cooled with subcooled He-II    L. Dresner Summary: A rapid, semiempirical method is presented for calculating the stability margins of superconductors cooled with subcooled He-II. Based on a model of Seyfert et al., the method takes into account both time-dependent Gorter-Mellink heat transport and the effects of interfacial Kapitza resistance. The method has been compared favorably with heat transfer data of Seyfert et al., stability data of Meuris, and stability data of Pfotenhauer and van Sciver.         Quenching in epoxy-impregnated superconducting solenoids: Prediction and verification    C. Joshi, J. Williams and Y. Iwasa Summary: An experimentally verified model that predicts quenching characteristics of a multi-section, epoxy-impregnated superconducting solenoid is described. The model uses a semi-empirical relationship to correlate the turn-to-turn normal zone growth to the propagation along a single wire. Normal zone growth in a solenoid is modeled assuming that transverse propagation is dominant. The computer predictions are compared with experimental results from small multi-section solenoids. The coil currents and terminal voltages predicted by this model agree with the experiments at high currents. However, at low currents the agreement is less satisfactory. The reasons for the dissagreement are understood and explained.         Experimental investigations on the stability of a He II cooled superconducting solenoid    J. Pfotenhauer Summary: Studies of the stability of a single layer superconducting solenoid are reported. In order to investigate various aspects of the stability of proposed designs, the solenoid is cooled with a concentric and confined layer of He II at 1.8 K and 0.1 MPa. Stability boundaries are measured for variety of types of thermal disturbances. It is found that these boundaries are insensitive to the duration of the thermal disturbances for disturbances less than 10 ms but are influenced by the spatial extent of those disturbances. A precipitous drop in the stability boundary at high currents is shown to be associated with the Kapitza resistance between the conductor and the liquid helium in agreement with existing theories. Results are presented on the development of normal zones in various conditions. These reveal spreading above a threshold of pulse energy density. Further, normal zone development in quench situations is shown to be useful in defining a relationship between the duration of the stability process and the joule heating of the conductor.         Quench pressure analysis of adiabatically stable magnets    E. Ibrahim, M. Hilal and S. Peck Summary: Adiabatically stable magnets are used in applications such as magnetic resonance imaging and high energy physics. The maximum pressure induced during a quench is more severe for long magnets such as dipole magnets required in constructing the Superconducting Supercollider (SSC). Following an adiabatically stable magnet quench, joule heating is generated through the magnet windings causing helium heating and inducing flow both within the windings and along the magnet cooling channel. The helium trapped in the windings is expelled as it is heated, transferring energy to the helium coolant in the channel. The maximum pressure during a quench strongly depends on the magnet length and is higher for longer magnets. To determine the maximum pressure induced in the cooling channel, it is necessary to simultaneously solve the time-dependent continuity, momentum, and energy equations for the helium flow in the channel, the heat conduction equation in the windings, and the current decay equations. A quasi-steady state solution of the fluid flow equations is valid as long as the magnet length divided by the speed of sound ratio is much less than the quench time. This particular case can be analyzed using General Dynamics code MAGPRES (1) and will not be discussed in this paper. The analytical approach, including the model developed to determine the mass and energy transfer associated with the helium flow from the windings, is presented in this paper. Quench pressure results employing a simplified model of an adiabatically stable magnet are also presented for some special cases to test the newly developed General Dynamics computer code QMAG. Also included are results of one computer run for SSC dipole magnets for the case of uniform quenching. The computer code will be used for more detailed analysis of SSC magnets; the results will be published as they become available.         Heater induced quenches in SSC model dipoles    W. Hassenzahl Summary: A 1-m long SSC dipole constructed at the Lawrence Berkeley Laboratory was subjected to a series of heater induced quenches to determine: axial quench propagation velocities, transverse quench propagation, and conductor temperature rise. Quenches were produced by 3 heaters at different locations in the magnet and at several currents. The results of these studies are described and are compared to previously published theoretical studies of quenches on the SSC dipoles. These results are shown to be in agreement with the calculations of the program "QUENCH", which includes an increase of the quench velocity during the first few milliseconds of the quench.         Quench propagation across the copper wedges in SSC dipoles    A. Ghosh, K. Robins and W. Sampson Summary: The effect of copper wedges on quench propagation in SSC windings, has been studied. The results indicate that the turn-to-turn quench transit time for conductors separated by an insulated copper wedge can be predicted with reasonable accuracy from the bulk quench properties and the mean wedge thickness.         Argon bubbles in sputtered amorphous Nb/sub 3/Ge films, studied by collective fluxpinning and transmission electron microscopy    A. Pruymboom, P. Berghuis, P. Kes and L. de Schepper Summary: We studied the effect of argon bubbles on flux-pinning in bias sputtered amorphous Nb/sub 3/Ge films. TEM was used for the determination of the bubble density distribution. A comparison is made with current theories on the elementary pinning force of a void.         Spin-polarized tunneling study of thin superconducting films in contact with magnetic insulators    J. Tkaczyk and P. Tedrow Summary: Spin-polarized tunneling on thin aluminum films in contact with the oxides of several rare earth oxides is used to measure the Zeeman splitting of the superconducting density of states. The splitting is found to be 2/spl mu/(B+B*) where B is the magnetic field applied parallel to the film surface and B* is of the order of /spl mu/M, the magnetization of the rare earth oxide. A possible explanation for the enhancement B* involves a coupling to either the magnetization or exchange field of the magnetic insulators via tunneling of quasiparticles into the insulator from the Al film. The magnitude of B* increases approximately inversely proportional to the film thickness of the Al-supporting such a proximity effect type model. The critical field of the bilayer is compared to that of a bare Al film as a function of the angle between the magnetic field and film surface.         Critical fields and spin polarized tunneling measurements of very thin V/sub 3/Ga films    J. Tkaczyk and P. Tedrow Summary: The critical fields of V/sub 3/Ga thin films have been measured with the field applied both perpendicular and parallel to the film surface. A transition from three to two dimensional behavior is noted as a function of thickness. Spin polarized tunneling measurements are presented for junctions fabricated with Al/sub 2/O/sub 3/barriers and Fe counter electrodes onto 10 nm thick films of V/sub 3/Ga. Unexpectedly low values for the spin-orbit scattering rate and effective g-factor are inferred from the tunneling measurements. This result is consistent with critical field measurements.         Nb/sub 3/Al and Nb/sub 3/(Al,Ge) composite tapes fabricated by CO/sub 2/laser beam irradiation    H. Kumakura, K. Togano, K. Tachikawa, Y. Yamada, S. Murase, M. Sasaki and E. Nakamura Summary: Nb/sub 3/Al and Nb/sub 3/(Al,Ge) tapes with excellent superconducting properties were fabricated by the laser beam irradiation method. Nb-25 at %Al and Nb-20 at % Al-5 at % Ge tapes were prepared by the powder metallurgy process. Continuous CO/sub 2/laser beam irradiation was carried out on the tape surface in an argon gas atmosphere at 1-13m/min, velocities. Beam power was 0.3-4kW and beam diameter at the tape surface was 0.5-3mm. As the power density was high and irradiation time was short, the tape could be heated and cooled much faster than a tape that was heat treated by the conventional method. The results were fine grain structure and large J/sub c/values at high magnetic fields. T/sub c/for an as-irradiated tape was 16-18K. This T/sub c/increased by /spl sim/2K by the subsequent annealings at 700/spl deg/C for 100 hours. The maximum T/sub c/(onset) values obtained were 18.6K for the Nb/sub 3/Al tape and 20.1K for the Nb/sub 3/(Al,Ge) tape, which indicated that stoichiometric compounds could be formed by laser beam irradiation. Annealed tapes, after the irradiation, showed excellent J/sub c/values, especially at high magnetic fields. J/sub c/values over 2x10/sub 4/A/cm/sup 2/at 23 Tesla were obtained for both Nb/sub 3/Al and Nb/sub 3/(Al,Ge) tapes. These values are much larger than those obtained by conventional heat treatment. J/sub c/values of as-irradiated tapes at high fields were smaller than those for annealed tapes, due to the lower T/sub c/and, hence, lower H/sub c2/. The large J/sub c/values, as well as easy scale-up procedure, indicate that the laser irradiation method is promising for the fabrication of advanced superconductors, e.g. Nb/sub 3/Al and Nb/sub 3/(Al,Ge) capable of generating fields over 20 Tesla.         Nb/sub 3/Al and its ternary A15 compound conductors prepared by a continuous liquid quenching technique    T. Takeuchi, K. Togano and K. Tachikawa Summary: The Nb/sub 3/Al, Nb/sub 3/(Al,Ge) and Nb/sub 3/(Al,Si) tapes have been successfully fabricated by a continuous liquid quenching using a high-speed moving copper, Cu, substrate tape heated at a proper temperature. A small amount of silicon, Si, and/or germanium, Ge, substituted for alminum, Al, improves the fluidity of molten alloy and facilitates the formation of the quenched alloy tape. The Nb/sub 3/Al alloy with small contents of Si(Ge) showed a supersaturated bcc phase as quenched state. This bcc alloy was then transformed into a metastable stoichiometric A15 phase, which had an extremely small grain size of a few hundred angstroms. The increase in Si(Ge) contents in the alloy led to the direct formation of A15 phase from the molten state, whose grain size was about 1 /spl mu/m. J/sub c/of the sample transformed from the bcc phase is much larger than that of the A15 phase directly formed from the molten state because of the finer grains in the transformed A15 phase. The highest J/sub c/at 20 T and 4.2 K of about 10/sup 5/A/cm/sup 2/was obtained for Nb-25 at % Al-2 at %Si alloy annealed at 820/spl deg/C for 3 h.         Preparation of high field Nb/sub 3/Al and Nb/sub 3/(Al,Ge) superconducting tapes by an electron beam annealing    K. Togano, H. Kumakura and K. Tachikawa Summary: Nb/sub 3/Al and Nb/sub 3/(Al,Ge) tape superconductors with excellent high-field properties have been successfully prepared by an electron beam annealing. The electron beam irradiation was performed on Nb-25at.%Al and Nb- 20at.%Al-5at.%Ge composite tapes moved at a velocity of 6m/min.. The accelerate voltage, current and diameter of the electron beam were 20kv, 5-20mA and 0.5-3mm, respectively. During the irradiation, the Al fibers reacted at a high temperature with surrounding Nb matrix to form A15 phase with stoichiometric composition. T/sub c/'s above 17K have been easily obtained after the electron beam irradiation, which can be increased by 1-2K by the following low temperature annealing at 700-800/spl deg/C. Maximum T/sub c/'s attained for Nb-Al and Nb-Al-Ge tapes are 18.4K and 19.8K(midpoint), respectively. The J/sub c/-H curves show no degradation in high magnetic fields up to 23T, exceeding 10/sup 4/A/cm/sup 2/. The highest overall J/sub c/(for irradiated area) at 23T and 4.2K is 3x10/sub 4/A/cm/sup 2/obtained for the Nb-Al-Ge tape. A new continuous irradiation system has been developed to fabricate longer tape of 10-100m.         Ti added Nb/sub 3/Sn wires by new fabrication processes    O. Kohno, Y. Ikeno, N. Sadakata, M. Sugimoto, K. Agatsuma and K. Kaiho Summary: The new fabrication processes for Ti addition to Nb/sub 3/Sn have been developed. Using the pure Ti around Nb cores and sufficient Sn by internal plating, we have been able to get the good workability during drawing to a final diameter and the high critical current density at a higher field than 14 T. Several characteristics of both Ti foil and Ti rod processes have been discussed about the effect of Ti addition to Nb/sub 3/Sn.         Liquid phase sintering and the use of Nb-H powder for preparing Cu-Nb/sub 3/Sn wires    O. de Lima and A. de Razende Summary: Cu-Nb/sub 3/Sn wires were prepared by the liquid phase sintering method. A Nb-H powder was used instead of the conventional and more expensive pure Nb powder. The pressed ingot of Cu-30wt%(Nb-H)-0.3wt%Al was degassed and heat treated under vacuum in the region of Cu liquid phase (T = 1200/spl deg/C). The hydrogen released during the process acts as a reducing atmosphere, and also as an activation agent promoting the wetting between liquid copper and niobium, leading to soft, highly dense Cu-Nb sintered samples. Tin diffusion and reaction were made by external and internal processes. In the latter case cores of tin rich alloy were used, and the occurrence of hard /spl eta/-phase precipitates was identified. The critical temperature is in the range of 16.0 /spl sim/ 16.8K, and the critical current density is around 10/sup 5/A/cm/sup 2/at H = 7T.         Effects of irradiation and strain in a bronze processed multifilamentary Nb/sub 3/Sn superconducting composite    T. Okada, M. Fukumoto, K. Katagirl, K. Saito, H. Kodaka and H. Yoshida Summary: The influence of fast neutron irradiation on critical current I/sub c/, mechanical properties and the strain dependence of I/sub c/for a bronze processed fine multifilamentary Nb/sub 3/Sn superconducting composite has been investigated. The neutron irradiation has been performed in a fission reactor at the reactor ambient temperature (<355 K) up to a neutron fluence of 3.6x10/sup 19/n/cm/sup 2/(E/sub n/>0.1 MeV). The effect of annealing after irradiation has also been investigated. It has been found that the composite grows harder and more brittle with irradiation. The strain which gives the maximum I/sub c/in I/sub c/vs. strain relation is increased with irradiation. The reversibility of strain induced change in I/sub c/is degraded by irradiation. Annealing at 723 K and 973 K (2 hr) after 3.6x10/sup 19/n/cm/sup 2/irradiation recovered successively the mechanical properties and strain dependence of I/sub c/up to the levels before irradiation.         Changes in superconducting properties by room temperature neutron irradiation for binary and alloyed Nb/sub 3/Sn multifilamentary wires    F. Weiss, R. Flukiger, W. Maurer, P. Hahn and M. Guinan Summary: The critical parameters T/sub c/, J/sub c/and B*/sub c2/of binary and Ta, Ti, Ni+Zn alloyed multifilamentary Nb/sub 3/Sn wires have been determined after room temperature irradiation at the 14 MeV neutron source in Livermore. J/sub c/measurements were made in transverse magnetic fields up to 20 T. In all the investigated cases, neutron irradiation caused an initial enhancement of J/sub c/, followed by a decrease at higher doses. In the alloyed wires the enhancement in J/sub c/occurs at much Lower doses with respect to binary wires (between 1.5 and 3x10/sup 17/n/cm/sup 2/depending on the alloying element. In the high fluence region (above 10/sup 18/n/cm/sup 2/) for alloyed wires J/sub c/is considerably reduced below the initial J/sub co/value measured in unirradiated samples, while for binary wires the J/sub co/values at 3x10/sup 18/n/cm/sup 2/are still higher than J/sub co/. In binary wires, B*/sub c2/is increased by about 10% at J/sub cmax/, in contrast to alloyed wires, where this initial increase is considerably reduced. Changes in the electrical resistivity /spl sigma//sub o/are used to explain the trends observed in the different samples.         Effect of atomic ordering and composition changes on the electrical resistivity of Nb/sub 3/Al, Nb/sub 3/Sn, Nb/sub 3/Ge, Nb/sub 3/Ir, V/sub 3/Si and V/sub 3/Ga    R. Flukiger, H. Kupfer, J. Jorda and J. Muller Summary: The electrical resistivity /spl sigma//sub o/has been measured on a Nb/sub 3/Ir sample, on a series of V/sub 3/Si single crystals with compositions between 20 and 25.5 at.% Si and on two Nb/sub 3/Al samples with the compositions /spl beta/ = 0.236 and 0.245. For Nb/sub .755/Al/sub .245/, /spl sigma//sub o/= 48.2x10/sup -8//spl Omega/m was measured after quenching from 1940/spl deg/C, a subsequent prolonged anneal at 750/spl deg/C leading to a reduction of /spl sigma//sub o/to 32.8x10/sup -8//spl Omega/m. It is found that /spl sigma//sub o/is more adequate than T/sub c/in describing high T/sub c/A15 superconductors at near-stoichiometric compositions. A comparison of the behavior of /spl sigma//sub o/vs. /spl beta/ shows almost identical dependence for Nb/sub 3/Ge and the two perfectly ordered systems Nb/sub 3/Sn and V/sub 3/Si thus suggesting perfect ordering for Nb/sub 3/Ge, too. The systems Nb/sub 3/Al and V/sub 3/Ga are found to exhibit substantially higher /spl sigma//sub o/values, reflecting deviations from perfect ordering, S/sub a/= 0.97 and S = 0.98, respectively. Consequences for the behavior of B/sub c2/in high field A15 multifilamentary wires are drawn.         High field properties of multifilamentary (Nb-4at%Ta)/sub 3/Sn    S. Foner, E. McNiff Jr., G. Ozeryansky and R. Schwall Summary: A series of multifilamentary (Nb-4at%Ta)/sub 3/Sn wires with varying Sn content was examined inorder to optimize the high field performance. Various Sn thicknesses were plated onto sections of 0.15 mm (.006") o.d. multifilamentary wire for external bronze processing. Long heat treatments achieved almost complete conversion of the filaments to A15. A systematic increase in B/sub c2/, J/sub c/and T/sub c/was measured for these wires with increasing Sn content. The highest measured values were B/sub c2/(4.2K)=27.8T (resistive mid-point),J/sub c/(4.2K)=1.5x10/sup 4/A/cm/sup 2/(overall) at 20T, and T/sub c/=17.8K. These values appear to be the highest reported for multifilamentary, bronze processed, ternary (Nb-X)/sub 3/Sn. The narrow (<1T) B/sub c2/transition suggests a uniform homogeneous A15. When the precompression due to the bronze matrix was removed, the values of J/sub c/(4.2K) increased by 40 to 50% in fields of 18 to 22T, but only a slight increase (<0.5T) in B/sub c2/(4.2K) was detected. J/sub c/increases by a factor of about 3 as temperature is reduced from 4.2 to 1.5K.         Hot extrusion and fabrication of powder metallurgy processed superconductors    S. Pourrahimi, C. Thieme and S. Foner Summary: In order to demonstrate the potential of powder metallurgy (P/M) process for fabrication of high field superconductors, intermediate scale (5 cm o.d. 15 cm long) billets were fabricated and processed industrially by hot extrusion. Precompacted powder composites of Cu-45wt%Nb and Cu-45wt%(Nb-1.2wt%Ti), each weighing more than 2kg, were extruded as solid or tubular bars. Sections of the extruded Cu-Nb and Cu-Nb(Ti) bars were successfully processed to 0.25 mm o.d. wires. Internal Sn sources were used to produce multifilamentary Nb/sub 3/Sn and Nb/sub 3/Sn(Ti). The high field critical current density was comparable to that obtained from small scale cold hydrostatic extrusion processing. The results suggest that large scale extrusion processing should produce high performance P/M processed superconductors.         High field NbN superconductor on a fiber basis    M. Dietrich, D. May, V. Windte, W. Schauer, F. Schmaderer and G. Wahl Summary: Thin films of niobium nitride with superconducting transition temperatures of 16 K have been deposited on commercial carbon fibers, sapphire, glass, and molybdenum without intentional heating by dc reactive magnetron sputtering. Two fiber transport chambers enable continuous coating of technical substrates. The effects of deposition conditions on the NbN formation, microstructure, resitivity, superconducting properties and on homogenenous coating of complex substrates have been studied with X-ray analysis, SEM, RBS and TEM. Small test coils have been fabricated.         High field properties of NbN conductors on practical substrates    R. Kampwirth, D. Capone II, K. Gray, H. Ho and S. Chumbley Summary: A new UHV, oil free, two gun magnetron sputtering system has been developed to allow continuous production of NbN conductors. A scaling rule relating film properties to preparation conditions was successfully used to predict the preparation conditions necessary to achieve the best NbN film properties in the two gun system. Comparison of high field J/sub c/results between the new two gun system and a diffusion pumped one gun system show similar results for NbN on sapphire substrates, suggesting no effect from oil backstreaming. Short sections of double side coated Ti tapes 25 /spl mu/m thick with /spl ap/5 /spl mu//m of NbN have J/sub c/=1x10/sup 4/A/cm/sup 2/at 18 T with H/sub c2/(4.2K) of 22.5 - 23 T. Ta wires made under the same conditions with /spl ap/2.7 /spl mu/m of NbN had J/sub c/(18 T) a factor of two lower. An 11 turn coil with a 2.5 cm bending radius has been made by coating one side of a moving tape 1.3 m long with /spl ap/3 /spl mu//m of NbN. The best section had a J/sub c/=1x10/sup 4/A/cm/sup 2/at 18 T and J/sub c/=4x10/sup 3/A/cm/sup 2/at 20 T.         Metal organic chemical vapor deposition of the Niobium-Nitrogen-Carbon system    E. Cukauskas, R. Holm, A. Berry, R. Kaplan and M. Green Summary: Niobium carbonitride films have been deposited by the pyrolytic decomposition of bis-tolueneniobium and hydrazine onto directly heated, 1-10 /spl Omega/-cm, (100) silicon substrates for several growth conditions. Deposition rates as high as one micrometer per minute were achieved. X-ray diffraction studies indicated many films were multiphase NbCN with a grain size estimated to be approximately 2-34 nm. Auger analysis indicated that film composition ranged from near stoichiometric NbN to NbCN with oxygen contamination up to 7%. The superconducting transition temperature ranged from 2 to 11K and the transition width was less than 80 mK in some of these materials. Films grown with no hydrazine had transition temperatures below 4K. X-ray diffraction studies of these nitrogen-free materials indicated an fcc structure with a lattice parameter of 4.47/spl Aring/, comparable to that of NbC. Resistivity ratios ranged from 0.5 to 0.9 for those films measured.         Upper critical field measurement and penetration depth determination for superconducting NbCN films    J. Moodera, T. Francavilla and S. Wolf Summary: High T/sub c/, low resistivity NbCN films were prepared by rf sputtering in a reactive gas mixture of Ar, N/sub 2/and cyanogen. Upper critical field for parallel and perpendicular orientation of the films to the applied field were measured systematically from T/sub c/down to 1.5 K. The critical field anisotropy is anomalous i.e.,H\min{c2}\max{\perp} > H\min{c2}\max{\parallel}for films sputtered at lower substrate temperature, whereas it shows normal behavior for films deposited at T/sub s//spl sim/ 1100/spl deg/C. This behavior is similar to that in sputtered NbN. The measured critical current in the presence of an applied magnetic field is lower than that in NbN of comparable properties. The penetration depth, /spl lambda/(0), was determined by measuring the self inductance of these NbCN films using it as an inductor in an LC oscillator circuit driven by a tunnel diode. It appears that NbCN films have lower /spl lambda/(0) than sputtered NbN films. The fact that NbCN films have higher T/sub c/, lower /spl rho/ and lower /spl lambda/(0) makes this a somewhat better superconductor for superconducting electronics applications.         Characterization of NbC/sub x/N/sub 1-x/films reactively sputtered in (Ar, N/sub 2/, C/sub 2/H/sub 4/) mixtures    M. Tonouchi, T. Kobayashi, Y. Nakato and H. Tsubomura Summary: Niobium-Carbon-Nitrogen ternary system was prepared by reactive sputtering in a mixture of argon, nitrogen, and ethylene. ESCA study made it clear that carbon co-exists in the prepared films, combining chemically with niobium, and mol-fraction of the carbon in the films can be controlled by the intermixture amount of ethylene. Co-sputtering with ethylene brought about many effects in the properties: very slight addition of ethylene (0.1-0.2%) was sufficient to provide the films with the higher transition temperature, 15.9K, the much higher density of the electron number density, and the lower resistivity as compared with the NbN films. Chemical analyses for the surface oxidation mechanism were closely done, showing that the NbCN and NbN films have no or much thinner NbO layer than the Nb film. The decrease of the electron number density as well as the mobility with lowering temperature in the NbN and NbCN films were observed by the Hall measurement, which explains the observed negative temperature coefficient of the resistivity.         Synthesis of MoN and RuN by active nitrogen sputtering    H. Ihara, N. Terada, K. Senzaki, M. Hirabayashi, Y. Kimura, R. Uzuka, F. Kawashima, M. Akimoto and H. Kezuka Summary: MoN films with B1 and hexagonal phases were prepared by active nitrogen sputtering with the aid of activated nitrogen species. High-Tc MoN films (above 14 K) were synthesized by NO sputtering gas which is favorable to produce active nitrogen atoms. Tc of B1 and hexagonal mixed-phase films was higher than that of each single phase film. RuN/sub x/films which consist of B1-like RuN and hexagonal Ru had T/sub c/of 9.1 K. High-pressure-annealed film attained the highest Tc of 16.4 K among the Mo-N system for a B1 and hexagonal mixed-phase. Ru-N films (high-pressure-annealed) had Tc of 10.1 K.         Formation, properties, and ion irradiation effects of hexagonal structure MoN thin films    D. Christen, S. Sekula, J. Ellis, J. Lewis and J. Williams Summary: Thin films (100-120 nm) of hexagonal structure MoN have been fabricated by reaction of Mo films in an NH/sub 3/atmosphere. The as-formed films possessed superconducting transition temperatures T/sub c//spl sime/ 13 K, with resistance ratios r = R(296K)/R(T/sub c/) in the range 5 to 10, low-temperature normal state resistivities /spl rho//sub o/= 4 to 10 /spl mu/ /spl Omega/-cm, and extrapolated upper critical fields H/sub c2/(0) = 4.0 to 5.0 T. Thin film X-ray diffraction patterns revealed no visible second phase, with measured lattice parameters close to literature values. The effects of lattice disorder on the superconducting and electronic properties were investigated by irradiation with nitrogen ions of energy 45 and 340 keV, resulting in a nearly uniform damage profile without the introduction of any new chemical species. The results indicate that ordered hexagonal MoN shows some of the unusual properties characteristic of moderate-to-high T/sub c/transition metal compounds, but is relatively insensitive to degradation of the superconducting properties by lattice disorder. For ion fluences /spl Phi/ up to 2x10/sup 16/N-ions/cm/sup 2/, T/sub c/is found to decrease monotonically and saturate at 9.5 K, almost 3/4 the initial value, while H/sub c2/(0) undergoes a gradual increase to 11T.         High field performance of PbMo/sub 6/S/sub 8/superconductors    K. Hamasaki, K. Watanabe, T. Saito, T. Yamashita, T. Komata and K. Noto Summary: Critical currents in Chevrel-phase lead molybdenum sulphide have been measured at two temperatures as a function of applied magnetic field up to 30 T. Improved critical current densities J/sub c/'s were achieved with electroplating and diffusion processed PbMo/sub 6/S/sub 8/short-tapes. Increased J/sub c/values were obtained for a short heat-treatment at 1050/spl deg/C. We find a J/sub c/of /spl sim/ 5/spl times/10/sup 3/A/cm/sup 2/at 20 T and 4.2 K, and /spl sim/1 /spl times/ 10/sup 4/ A/cm/sup 2/at 20 T and 1.6 K. The dependence of J/sub c/on grain size was also measured, and the correlation between flux pinning force and average grain size is discussed. The critical current density in the field range of < 27 T was strongly dependent on the grain size, and the critical currents at 14 T and 4.2 K can be scaled by the inverse grain size.         Superconducting beryllium films deposited by ion-beam-sputtering    Y. Maeda, K. Takei, M. Okamoto, K. Nakamura and M. Igarashi Summary: The properties of beryllium thin films deposited by ion-beam-sputtering (IBS-Be) are investigated, IBS-Be films with high superconducting transition temperatures (T/sub c/'S = 6-7 K) have an amorphous-like structure. T/sub c/'s show thermal stabitlity up to 480 K. IBS-Be/BeO/Pb junctions with low leakage conductance indicate IBS-Be base electrodes do not deteriorate and that the Be-oxidized layers function as good tunnel barriers, The deduced value of the electron density of states at the Fermi level remains as low as that for bulk beryllium. IBS-Be films are considered to be advantageous for applications to tunneling and Abrikosov vortex devices.         Development of manufacturing techniques to prepare V/sub 2/(Hf-Zr) Laves phase (C15) superconductor    D. Hazelton Summary: Superconducting material based upon the V/sub 2/(HF-Zr) Laves Phase system has been prepared utilizing Commercially scaleable processing techniques. This paper covers the examination of several processing methods by which a V (Hf-Zr) Laves Phase superconductor could be fabricated. These methods include hot extrusion of billets containing V, Hf, and Zr components in either powder or foil form incorporated with stabilizing Cu protected by a Nb diffusion barrier. Cold processed billets of similar composition were also investigated. These materials were then drawn with intermediate anneals to wire (1.626mm to 0.305mm dia) with varying degrees of difficulty. Wire samples were then heat treated from 900-950 deg C to form the Laves phase material via interdiffusion of the V, Hf, and Zr components. Scanning electron microscope (SEM) examinations were conducted on the various samples and critical current densities measured.         Proximity coupling of surface acoustic waves to a superconducting Al/sub x/O/sub 1-x/film    A. Schenstrom and M. Levy Summary: We present the first preliminary results on proximity coupling of surface acoustic waves (SAW) to a superconducting Al/sub x/O/sub 1-x/film. The aluminum film was evaporated onto a glass substrate in a partial pressure of oxygen. The glass was then placed, with the film face down, between a pair of SAW transducers on a piezoelectric LiNbO/sub 3/substrate. Mechanical coupling between film and SAW was very weak and any attenuation of the SAW by electron-phonon interaction could be neglected. The SAW was attenuated by the coupling to the film of the piezoelectric field that the SAW produced. We found a large decrease in attenuation when superconductivity starts to appear in the film.         A possible technique for determining the average grain size in thin granular superconducting films    J. Schmidt and M. Levy Summary: A new technique is proposed by which it may be possible to determine the average grain size of a thin superconducting film from measurements of the electrical resistance and the surface acoustic wave (SAW) attenuation. This technique is based on a percolation model for the SAW attenuation and resistance in a granular superconducting film. In essence, the model claims that as the grain size becomes comparable to the SAW wavelength, one should observe differences between the measured SAW attenuation and the attenuation predicted by acoustoelectric coupling of the SAW to the film. By measuring the SAW attenuation and comparing it the theoretically predicted value for the acoustoelectric attenuation (which is proportional to the normal state resistance of the film), one can determine the average grain size of the film. This technique would have two main advantages over conventional techniques used to measure grain size. First, the technique would not alter or destroy the sample. Secondly, the technique could be adapted to make in-situ measurements of the grain size of the film. In this paper we will review the underlying theory and present experimental data which gives qualitative support for the use of this method.         Capability of a MM-wave mixer with Nb/Al-AlO/sub x//Nb SIS junction    T. Kasuga, M. Tsuboi, J. Inatani, H. Iwashita and A. Sakamoto Summary: Characteristics of a millimeter-wave mixer with Nb/Al-AlOx/Nb SIS junction were calculated along the 3-port mixer treatment. Signal and intermediate frequency dependences are obtained. The results show that the mixer has conversion gain between signal frequencies of 30 and 250 GHz. Intermediate frequency up to 10 GHz can be used in the USB mode.         An analytical method for stationary oscillations in superconducting circuits    K. Katori, M. Otake and M. Morisue Summary: This paper describes an analytical method of making a study of stationary oscillations produced in a superconducting circuit such as a Josephson oscillator or Josephson mixer. The principle of the method is based on solving simultaneous polynomial equations obtained from the harmonic balance method. The theory of the analysis is described and some examples of applying this method to a Josephson oscillator are illustrated. It is shown that the numerical results given by this method are in good agreement with those of computer simulations.         Oscillation modes in the tunnel type and the weak-link type Josephson junctions    K. Araki, M. Morisue, H. Kasahara and S. Yamamoto Summary: The present paper discusses in detail the oscillation modes and these dependency on system parameters in the tunnel type and weak-link type Josephson junctions driven by dc and rf current sources.         Phase-locking in distributed arrays of Josephson oscillators    J. Sauvageau, A. Jain, J. Lukens and R. Ono Summary: Arrays of Josephson junctions can be used as voltage tunable oscillators at millimeter and submillimeter wavelengths. However proper circuit design is required to achieve the phase-locking of the junctions required for coherent radiation. The design of arrays of Josephson junctions distributed over many wavelengths is discussed and data are presented on the strength of the phase-locking in these systems. With proper design and optimization substantial power at frequencies above 100 GHz is predicted.         Experimental study of mutual phase locking in Josephson tunnel junctions    L. Kuzmin, K. Likharev and E. Soldatov Summary: Strong mutual phase locking of Josephson oscillations in unshunted tunnel junctions in-coporated into a special common millimeter-wave resonance structure has been observed and studied. The observed locking range was especially wide (up to /spl plusmn/10%) when the both junctions were dc biased at the current steps corresponding to the common resonance modes (frequencies from 25 to 200 GHz). Main features of the junction interaction have been found to be in a qualitative agreement with our earlier theory developed for lumped junctions. For larger junctions (S = 30 X 30 /spl mu/m/sup 2/), quantitative deviations from the theoretical predictions have been observed and identified as resulting from interaction of the (external) common resonance mode with the (internal) Fiske modes of the junctions.         Quantum noise in the quantum theory of mixing    M. Feldman Summary: The minimum noise temperature obtainable in the quantum theory of mixing, allowing arbitrary terminations at all considered frequencies, is shown to be h/spl omega//2k, the same result as for other high-gain linear amplifiers. The conditions for attaining this absolute minimum noise appear to be fulfilled in only two cases, approximated by the super-Schottky mixer with large LO, and by the SIS mixer with small LO. For the ideal SIS mixer, the minimum noise requires one particular value of source impedance, regardless of the image termination. The origin of the quantum noise is discussed.         A study of applied microwaves and quasiparticle injection on the dynamically enhanced supercurrent of a microbridge    H. Smith, M. Dion and R. Escudero Summary: We have measured the influence of external excitations on the dynamically enhanced critical current of a superconducting microbridge. In one experiment microwaves were applied to a microbridge and the dynamically enhanced critical current was monitored. In a second experiment, two superconducting microbridges were fabricated closer together than a coherence length. The dynamically enhanced critical current of one microbridge was measured as a function of the current through the second microbridge. In each experiment the dynamically enhanced critical current was found to be changed. A qualitative explanation of this effect is discussed.         Period three generation on microwave-induced constant-voltage steps of Josephson tunnel junctions    J. Mygind, J.B. Hansen, J. Clarke, G. Ovsyannikov and H. Svensmark Summary: We report the observation of one-third harmonic generation in small Josephson tunnel junctions driven with a microwave signal in the frequency range 8 to 18 GHz. This phenomenon was observed both with the junction biased in the zero voltage state and on microwave-induced constant-voltage steps in the current-voltage characteristic. With high levels of applied microwave power the period-tripled signal was detected on steps up to order 120.         DC SQUIDS made of NbN/a-Si/NbN tunnel junctions    S. Kuriki, M. Matsuda and A. Noya Summary: We have fabricated planar dc-SQUIDs using all hard metal NbN/a-Si/NbN tunnel junctions. The a-Si barrier is oxidized to block pinholes in an rf plasma. The SQUIDs have a square-washer coil with an inductance of 0.2-0.3 nH; two 4 /spl mu/m X 4 /spl mu/m junctions are shunted by resistors of a-Nb/sub 3/Ge films. An Auger analysis has shown that the a-Si is fully oxidized by the plasma oxidation, but the barrier in the junction is a mixture of Si and Si oxide, indicating a reaction between oxygen of the barrier and Nb of the counter NbN film. We have operated the SQUIDs in a flux-locked loop at a modulation frequency of 92 kHz. The power spectrum of the flux noise has a strong 1/f component which agrees with calculation assuming the temperature fluctuation of the critical current as a main source. At high frequencies the noise spectrum is white at 10/sup -10//spl phi//sub 0//sup 2//Hz including an electronics system noise.         Transient and continuous responses of neuromagnetic fields evoked by peripheral nerve stimulation    S. Kuriki, Y. Mizutani and Y. Isobe Summary: We measured neuromagnetic fields evoked by stimulation of the ulnar nerve using an rf SQUID with a second-derivative gradiometer. Responses to transient stimulus obtained at various positions of the lateral head were used to calculate location and strength of an equivalent current-dipole source by least-squares fit. The dipole location corresponded to the primary somatosensory area. We also measured continuous responses to repeated stimuli, where lag of phase of a component synchronous to the stimuli was detected. The phase lag was linear to the frequency of the stimuli in a limited frequency range. The slope of the linear variation gave latent time of the synchronous component, which agreed with the time of main peaks in the transient response.         Perfect modulation of critical currents of DC-SQUIDs with short weak links    H. Ohta Summary: In a small-loop-inductance limit, the crititcal currents of dc-SQUIDs of short weak links vanish periodically by increasing applied magnetic field monotonically. This means that the current-phase relations of our short weak links ( Quasi-Planar Junctions ) are almost sinusoidal and that the critical current of one short weak link is almost equal to that of the other short weak link in the dc-SQUID. It has been experimentally proved that these observations do not depend on weak link materials. These dc-SQUIDs are suitable for a switch of out fluxoid-type logic circuits as well as a sensitive magetometer.         Anomalous RF-characteristics of highly hysteretic point-contact SQUIDS    C. Gough, M. Keene and A. Rae Summary: Anomalies in the rf characteristics of Nb point-contact SQUIDS incorporating strong junctions have been investigated over a wide temperature range and are explained in terms of a model based on metastable multiple flux jumping loops.         Integrated microwave SQUID    A. Smith, R. Simon, J. Burch, R. Sandell and A. Silver Summary: We describe the properties of the single junction SQUID operated at microwave frequencies. The low inductance SQUID is fabricated in a thin film format and tightly coupled to an integrated superconducting transmission line and transformer. We discuss new modes of operation and opportunities for improved device and circuit performance.         Influence of the signal coil on DC-SQUID dynamics    H. Seppa and T. Ryhanen Summary: The dynamics of the dc-SQUID in the presence of a signal coil was studied. The signal coil creates an additive parasitic capacitance between the junctions and its self-resonance imports new features to the SQUID dynamics. Our results suggest that if a SQUID with smooth characteristics and low noise properties is desired, all the resonances present in the SQUID ring or in the flux coupling circuit should be damped properly. Low attenuation yields a system with high gain but with higher excess noise. On the other hand, heavy damping of the device yields low gain and a high noise level and thus a compromise is necessary.         DC-SQUIDs fabricated by electron beam direct writing    P. Carelli, V. Foglietti and R. Leoni Summary: An Electron Beam MicroFabricator (EBMF) has been used to write directly on a silicon wafer to obtain many equal chips containing dc-SQUIDs and superconducting test circuitry. We developed a complete lift-off technique on an electronic resist for all the seven needed layers of the process. The first layer, consisting of Au-Pd alloy, is used as resistor and for patterning the markers required to align the various layers. The calibration on such markers avoid the stitching problem due to the large chip dimensions (6.30 X 6.30 mm) as compared with the maximum range of the electron beam deflection. The direct writing permits alignment between the various layers better than 1um in any chip. The first test on the developed devices shows high reliability and flexibility of the overall process.         Intrinsic Johnson noise in a rf-SQUID: A numerical analysis    M. Cerdonio, M. Mazzer, A. Miotello and S. Vitale Summary: A numerical method able to account for the intrinsic thermal noise in a rf-SQUID is described. Indicative numerical results are illustrated.         Johnson noise from normal metal near a superconducting SQUID gradiometer circuit    J. Clem Summary: The effect of Johnson noise generated by normal metal in an otherwise superconducting SQUID gradiometer circuit is investigated theoretically. The generalized Nyquist theorem is applied to develop a simple method for computing the noise at frequencies less than the inverse of the normal metal's magnetic flux diffusion time. For gradiometers prepared using printed-circuit-board technology (superconducting lines deposited on copper substrate lines) the Johnson noise is predicted to generate white current noise at low frequencies. Since the power spectrum is proportional to the cube of the normal-metal thickness, the current noise can be of nearly the same order of magnitude as that which would be generated by the bare normal metal when the normal metal is sufficiently thick. The method also can be used to compute the Johnson noise generated by normal metal at solder joints, as well as by any normal metal in the vicinity of the SQUID input circuit, whether in electrical contact or not. The theoretical results indicate that, to limit the amount of Johnson noise generated by a SQUID gradiometer, one should avoid placing excessive quantities of normal metal close by.         The temperature dependence of magnetic fields trapped axially inside superconducting solenoids    T. Clem Summary: Experimentation on the thermal and magnetic properties of superconducting solenoids in magnetic fields much less than critical fields is reported. Specifically, this includes measurements on the temperature dependence of the intensity of axial magnetic fields trapped in the center bore of the solenoids. Solenoids wound of niobium, niobium titanium and niobium zirconium have been investigated. The evidence supports the conclusion that the major contribution to the temperature dependence of field intensity is attributed to penetration-depth changes in combination with a flux pinning effect. As was the case for the superconducting tubes reported in reference 2, anamolously large values of penetration depth have been determined for the wire samples. However, wider deviations from the Gorter-Casimir temperature dependence have been observed for the solenoids than for the tubes. It is believed that these deviations arise from material inhomogeneities and flux pinning. Wire diameter appears to be a critical parameter with the temperature dependence increasing as the diameter decreases. By means of a thermal switch, the effect of flux pinning has been quantified. Both reversible and irreversible flux pinning effects have been observed.         Phase shift effects of the I-V characteristics of zero-field current spikes in long Josephson junctions    A. Ferrigno, U. Gambardella and S. Pace Summary: In this paper we analyse the length dependence of the zero-field current spikes (Z.F.S.) which appear in the I-V current voltage characteristics of long Josephson tunnel junctions. ZFS are described in terms of travelling fluxons. The presence of the bias current, losses and in particular of the boundary conditions is discussed: in the absence of magnetic fields fluxons are reflected either at the junction edges or for antifluxon collisions. The generated phase shift effects are dominant with respect to the variations of the power balance condition. Taking into account the phase shift and the limit of the Lorentz fluxon contraction, we derive an analytical approximate expression of the mean velocity in one-dimensional, intermediate length, overlap junctions. A rather good agreement is obtained comparing our theoretical analysis with several experimental ZFS I-V characteristics.         Integrated gradiometer with large /spl Beta/ SQUID    K. Yoshida, S. Kohjiro, K. Enpuku and K. Yamafuji Summary: An integrated thin-film dc SQUID gradiometer utilizing large /spl beta/ SQUIDs is designed. A damping resistance in shunt with a SQUID inductance is introduced in order to improve the performance of large /spl beta/ SQUIDs. Usefulness of the damping resistance is verified both theoretically and experimentally, so that we can use large /spl beta/ SQUIDs without significant degradation of performance. Large /spl beta/ SQUIDs simplify a configuration of the coupling section between an input coil and the SQUID, and will be a useful method to realize both an efficient magnetic coupling and a high balance of the gradiometer.         SQUID-based rock magnetometer with open-ended horizontal room-temperature access    H. ter Brake, P.d. la Court, A. Lenferink, J. Ulfman and J. Flokstra Summary: We constructed a 3-channel SQUID-based rock magnetometer with an open-ended horizontal room-temperature access having an inner diameter of 38 mm. A refrigerator is incorporated for cooling two radiation shields so that an operating time can be realized of about 10 weeks with a reservoir volume of 26.7 litres. The temperature variation along the access is about 9 K. The rock magnetometer is equipped with a special sensing-coil set of which the signal uniformity with respect to magnetic dipoles is about a factor of two better than that of conventional vertical-access systems. The intrinsic noise level of the system is 10/sup -11/Am/sup 2///spl radic/Hz.         Analytical and numerical results for a long Josephson junction with surface losses    S. Pagano, N. Pedersen, S. Sakai and A. Davidson Summary: In this paper we show several analytical approaches to study the effect of dissipation on fluxon motion; our attention is mainly devoted to the surface impedance term which is the main quantity responsible for qualitative dynamical changes in the junction.         Measurements of the high frequency loss near the plasma resonance in Josephson tunnel junctions    J.B. Hansen, H. Svensmark, J. Mygind, S. Sakai and M. Samuelsen Summary: We here present measurements of the microwave loss near the plasma frequency (at 9 GHz) in two 30 X 30 /spl mu/m/sup 2/Nb-Nbox-Pb Josephson tunnel junctions with critical current density, J/sub c/, in the range 10 to 70 A/cm/sup 2/. The temperature and amplitude dependence of the high frequency loss is investigated and compared with the differential resistance of the dc characteristic.         The superconducting transition in a million Josephson element snap array    M. Bhushan, R. Cantor, J. Gordon, A. Goldman and F. Yu Summary: Square arrays of one million Josephson junctions have been fabricated using the Selective Niobium Anodization Process (SNAP). The arrays consist of 2.5 micron square Josephson junctions on a square lattice with a spacing of 29 microns. Clear evidence of a Kosterlitz-Thouless transition has been found in measurements of current-voltage charcteristics and resistance as a function of temperature. Measurements of the resistance vs magnetic field exhibit minima at fields corresponding to both one and one-half of a flux quantum in a fundamental cell.         Dynamic conductance of two-dimensional arrays of Josephson junctions    Ph. Lerch, R. Theron, Ch. Leemann and P. Martinoli Summary: The ac sheet conductance of large two-dimensional arrays of proximity effect SNS Josephson junctions was measured as a function of temperature, frequency and applied perpendicular magnetic field. A quantitative analysis of the data shows that the normal to superconducting transition of unfrustrated arrays follows the predictions of the Kosterlitz-Thouless theory for phase transitions in two dimensions.         Quantization of dielectric flux in phase-quantum-tunnel junction    N. Yoshikawa, M. Tayama, T. Akeyoshi, M. Kojima and M. Sugahara Summary: The electrical properties of relatively long bridges made of very thin NbN film were investigated experimentally. When the bridge resistance R/sub b/ /spl cong/100/spl Omega/ the I-V characteristic showed the possibility of quantization of dielectric flux inside the bridge. On the other hand, highly resistive bridges (R/sub b/ /spl cong/10K/spl Omega/) revealed a step structure in the IV relation when irradiated by electromagnetic waves. Since the current interval of the steps is proportional to the frequency of the wave, these bridges are thought to behave as phase-quantum-tunnel devices with properties dual to those of Josephson junctions.         Report on the stanford octagonal magnetic monopole detector    M. Huber, B. Cabrera, M. Taber and R. Gardner Summary: After 1008 active (1150 elapsed) days of operation, the 476 cm/sup 2/three-axis monopole detector has been shut down without observing any candidate events. This sets an upper limit for a cosmic ray flux of magnetic monopoles of 4.4x10/sup -12/cm/sup -2/s/sup -1/sr/sup -1/at 90% confidence level. We have constructed a 1.5 m/sup 2/(averaged over 4/spl pi/ solid angle) superconducting monopole detector and are testing its performance. The sensing area includes only coincident events. The detector is an octagonal cross-section cylinder with an independent planar gradiometer loop (16.9 X 521.2 cm) on each side of the octagon. Originally constructed with copper traces covered by lead/tin solder, the loops have been converted to 2 mm wide X 50 /spl mu/m thick niobium-titanium (NbTi) ribbon because of excessive noise in early tests. We expect to obtain a signal to noise ratio of about 10 with the new loops.         New results of the theory of set and bloch oscillations in small tunnel junctions    D. Averin and K. Likharev Summary: Effect of various factors upon the recently predicted new coherent oscillations in small tunnel junctions is analyzed. The factors under analysis include thermal fluctuations at nonvanishing temperature T, metallic conductance R\min{e}\max{-1}of the external circuits, and Josephson coupling characterized by its energy amplitude E/sub J/. As a result of the calculations, quantitative conditions of experimental observation and practical applications of the SET and Bloch oscillations and the associated dynamic effects are formulated.         Single-electron transistors: Electrostatic analogs of the DC SQUIDS    K. Likharev Summary: Dynamics of two simple structures (Fig. 2) comprising twin pairs of small tunnel junctions is analyzed. If the single-electron conductancesR\min{1.2}\max{-1}and capacitances C/sub 1.2/of the junctions are small enough (Eq 1), the dynamics is influenced drastically by e-quantization of the electrical charge Q of the central electrode. As a result, the structures become close analogs of the dc SQUIDs within the framework of the well-known electro\leftrightarrowmagnetic duality (Q\leftrightarrow\Phi, etc.). In particular, the dc I-V curves of the structures can be controlled by the "gate" voltage U, so that the devices can be used as "Single-Electron Transistors" (SETs) with characteristics resembling those of the usual FETs, but at a new quantitative level. Analysis shows that the physics of the SETs allows much smaller dimensions, higher cutoff frequencies and much lower power consumption than for their semiconductor counterparts. New transistors can be apparently used to achieve extremely large integration scales, possibly opening a way to three-dimensional and molecular-level integration.         Design of high-order superconducting planar gradiometers with shaped asymmetric near-source response    R. Bain, A. Jones and G. Donaldson Summary: We describe the solution of the general problem of designing an N-th order planar gradiometer with m /spl ges/N crossovers, where the position of (m-N) of these crossovers is selected on near-source response criteria. The ability to pre-select certain crossover positions is valuable in many applications (e.g. biomedical, NDT) because it allows us to control specific properties of the near-source response such as (i) response peaking at specified locations (ii) zero-response at certain locations (iii) minimal coupling to near-sources, at each end of a gradiometer of arbitrary order. Examples are given for the important cases m = N+1 and m = N+2.         A novel modulation technique for 1/f noise reduction in dc SQUIDs    V. Foglietti, W. Gallagher and R. Koch Summary: We describe a novel modulation scheme for dc SQUIDs in flux locked loop applications that cancels the effects of Josephson junction critical current fluctuations. The scheme involves switching the SQUID between three states and detecting the output at the second harmonic of the modulation frequency. With this scheme we have achieved a ten fold reduction of the low frequency flux noise spectral density over that obtained with a conventional flux locked loop readout. A dc SQUID with a 20 pH inductance had a resultant noise spectral density of 10/sup -12/\Phi\min{0}\max{2}/Hz at 0.1 Hz, three times lower than the lowest flux noise previously reported for any SQUID system at this frequency.         Propagation and generation of Josephson radiation in superconductor/insulator superlattices alternately containing two different barriers    S. Song, P. Auvil and J. Ketterson Summary: The sine-Gordon equation for a Josephson coupled superconductor/insulator superlattice is derived using a Lagrangian formalism. This equation has essentially the same form as that given eariler by Kulik for a single Josephson junction but with different parameters. For the case of S/I superlattices alternately containing two different barrier thicknesses, the behavior of the propagation and generation of the Josephson radiation is governed by two coupled sine-Gordon equations, which results in two photon branches separated by a frequency gap. Some potential applications of these structures, involving increased outputs of the Josephson radiation and two hand filters, are discussed.         Macroscopic quantum coherence in a charge mode device    J. Gallop Summary: A possible test for macroscopic quantum coherence in weakly coupled superconductors is suggested. This involves measurement of the time evolution of a single excess pair charge, initially placed on one electrode of a weak-link.         Recent developments in flux pinning    P. Kes Summary: Considerable progress has recently been made regarding two fundamental aspects of flux pinning. A microscopic basis has been given for the elementary interaction potential of defects which are predominantly characterised by their electron scattering cross section. As a result new expressions have been derived for pinning by voids or bubbles, precipitates, and grain boundaries. Secondly, the puzzling threshold paradox for a system of weak, random pins has been resolved by the concept of collective pinning. The central issue of this concept is the positional disorder of the vortex lattice created by the interaction with the pinning centers. The relation between disorder, pin strength, pin density and bulk pinning force is better understood and may allow an estimate for the upper bounds of the critical current. These developments are briefly reviewed in this paper both regarding the theoretical background and their experimental verification.         Computer modeling of magnetic flux pinning by grain boundaries in high-field superconductors    D. Welch, V. Ghosh, O. Lazareth and R. Hatcher Summary: We report here some results for the critical current density of a high-field superconductor such as Nb/sub 3/Sn calculated with a simple two-dimensional model using computer simulation methods similar to those of Brandt[1] and utilizing an expression for the magnetic flux line-grain boundary interaction energy derived by Welch[2] based on the electron-scattering mechanism.         Is J/sub c/in Nb/sub 3/Sn limited by grain-boundary flux-shear?    D. Dew-Hughes Summary: It is postulated that flux-pinning by grain-boundaries may be avoided if flux can shear and flow down paths lying in grain-boundaries. The difference in flux-pinning behaviour between NbTi,F/sub p//spl alpha/ b(1-b), and solid state reacted Nb/sub 3/Sn,F/sub p//spl alpha/ b/sup 1/2/ (1-b/sup 2/, arises from the different morphologies of their grain-structures. The boundaries, drawn out parallel to filament axes and direction of current flow in NbTi act as effective barriers to flux motion. The boundaries of grain produced by reaction in Nb/sub 3/Sn provide paths along which flux can flow by grain-boundary shearing. An expression is developed for grain-boundary shearing which gives good agreement with experimental results.         Elementary pinning force for an isolated vortex    O. Hyun, J. Clem, L. Schwartzkopf and D. Finnemore Summary: The elementary pinning force for an isolated yortex has been measured, and procedures have been developed for systematically moving the vortex back and forth across a Josephson junction. Changes in the current-voltage curves for the Josephson junction as the vortex changes position provide an easy way to read out the location of the vortex.         Dependence of the shape of the resistive transition on composite inhomogeneity in multifilamentary wires    C. Plummer and J. Evetts Summary: The shape of the resistive critical current transition is an important factor in the specification of a multifilamentary superconducting composite. We have made a detailed analysis of the relation of the shape of the resistive transition to the scale and distribution of inhomogeneity within a composite. In particular we are able to show that the 'n-value' of a transition often has a simple inverse power law relation to the standard deviation of the spatial critical current distribution. The expression for the voltage at a particular current level depends on both the geometry of the composite and the detailed form of the critical current distribution. Two limits are discernable; the 'single filament' limit, applicable when a given filament conserves its transport current and the 'coupled filament' limit, applicable when current transfer between filaments dominates. The problem of deconvolution of an experimental transition to give the critical current distribution is discussed with specific reference to Nb/sub 3/Sn multifilaments. A method of analysis is outlined which combines data from both the resistive transition in a multifilament, and the resistive transition in single filaments extracted from the multifilament.         Determination of the average critical current from measurements of the extended resistive transition    W. Warnes and D. Larbalestier Summary: When stufying the correlation between the microstructral properties of a superconducting composite and its flux pinning characteristics, on typically uses the critical current as derived from a measurement of resistive transition to derermine the critical Korentz force.         Effect of filament diameter and spacing on J/sub c/of Nb/sub 3/Sn wires in the intermediate field range (10 - 12 T) and at high fields    W. Specking, F. Weiss and R. Flukiger Summary: Commercial binary and Ta alloyed Nb/sub 3/Sn wires (7.5 wt.% Ta) have been investigated in order to optimize J/sub c/in the intermediate field range (10 - 12 T) and at high fields, i.e. 16 T for the binary and 20 T for the Ta alloyed wire. For this purpose, the diameter of the as-received wires (0.86 mm) was further reduced to different sizes between 0.86 and 0.29 mm. For each diameter, the reaction conditions, i.e. temperature and time, were optimized. The results can be described as follows: a) The A15 layer growth in the Ta alloyed wire is slower than for the binary wire. b) In both wires, there is a cross-over of the J/sub c/vs. B curves at 14 T when reducing the diameter. The larger sizes have higher J/sub c/values above 14 T, while the thinner wires are better below 14 T. c) In both wires, an enhancement of the compressive strain, /spl epsiv/ up to 0.56%, as well as a substantial decrease of 8/sub c2/up to 3.3 T was observed after the reduction to 0.29 mm diameter. The drop in B/sub c2/and thus J/sub c/at high fields is correlated to an enhanced prestress in the thinner wires, attributed to reduced filament spacings (dispersion hardening). The reason for the enhancement of J/sub c/below 14 T for thinner wires is still a subject of investigation. The present work shows that the optimization of J/sub c/for binary and alloyed Nb/sub 3/Sn wires depends on the operational field range and leads to strongly different configuration requirements: For applications at fields B < 14 T, the filament diameter/ spacing ratio should exceed 8 /spl mu/m/1.5 /spl mu/m, while for fields below 14 T, the filament diameter- /spacing ratio should be of the order of 1 /spl mu/m/0.3 /spl mu/m. Both quantities, filament spacing and diameter, are correlated by the requirement of a maximum A15 content in the wire cross section.         Shape anisotropy in critical current densities of Nb/sub 3/Sn tapes produced by the bronze process    M. Suenaga, D. Welch and N. Higuchi Summary: A systematic study of the shape anisotropy in critical current densities of bronze processed Nb/sub 3/Sn tapes was made. [Critical current densities of the Nb/sub 3/Sn tapes are greater when applied magnetic field H is perpendicular, J/sub c/(/spl perp/), to the flat face of the tape than when it is parallel, J/sub c/(/spl par/), to the face while current is perpendicular to H in both cases.] In these tapes, the anisotropy is not only due to the shape (columnar or equiaxed) of the Nb/sub 3/Sn grains, but also in many cases, it is related to the similar anisotropy in the critical magnetic fields H/sub c2/. However, the origin of this shape anisotropy in H/sub c2/remains unknown.         Magnetic flux expulsion from superconducting shields    M. Fang, J. Clem and D. Finnemore Summary: A new type of magnetic shield has been Constructed for use with superconducting microelectronic circuits or other circuits requiring low ambient magnetic fields. Experimental verification of the basic flux sweeping action and flux expulsion is demonstrated for a wide range of conditions. The optimum temperature for flux sweeping is shown to be in a narrow window rather close to T/sub c/where the vortices are relatively mobile.         The superconducting super collider from a department of energy staff point of view    L. Temple Jr. Summary: The U.S. high energy physics community has given highest priority to the creation of a new forefront accelerator facility called the Superconducting Super Collider (SSC). A brief description of the proposed facility is presented. The scientific need for the SSC and the DOE mission it supports is described. Progress to date, through the Department of Energy (DOE) review and approval process, is reported. Near term and longer term possible actions are discussed.         Full length prototype SSC dipole test results    J. Strait, B. Brown, J. Carson, N. Engler, H. Fisk, R. Hanft, K. Koepke, M. Kuchnir, E. Larson, R. Lundy, P. Mantsch, P. Mazur, A. McInturff, T. Nicol, T. Ohmori, E. Schmidt, J. Theilacker, G. Tool, J. Cottingham, P. Dahl, M. Garber, A. Ghosh, C. Goodzeit, A. Greene, J. Herrara, S. Khan, E. Kelly, G. Morgan, A. Prodell, W. Sampson, W. Schneider, R. Shutt, P. Thompson, P. Wanderer, E. Willen, S. Caspi, W. Gilbert, W. Hassenzahl, R. Meuser, C. Peters, J. Rechen, R. Royer, R. Scanlan and C. Taylor Summary: Results are presented from tests of the first full length prototype SSC dipole magnet. The cryogenic behavior of the magnet during a slow cooldown to 4.5K and a slow warmup to room temperature has been measured. Magnetic field quality was measured at currents up to 2000 A. Averaged over the body field all harmonics with the exception of b/sub 2/and b/sub 8/are at or within the tolerances specified by the SSC Central Design Group. (The values of b/sub 2/and b/sub 8/result from known design and construction defects which will be corrected in later magnets.) Using an NMR probe the average body field strength is measured to be 10.283 G/A with point to point variations on the order of one part in 1000. Data are presented on quench behavior of the magnet up to 3500 A (approximately 55% of full field) including longitudinal and transverse velocities for the first 250 msec of the quench.         Construction of cold mass assembly for full-length dipoles for the SSC accelerator    P. Dahl, J. Cottingham, M. Garber, A. Ghosh, C. Goodzeit, A. Greene, J. Herrera, S. Kahn, E. Kelly, G. Morgan, A. Prodell, W. Sampson, W. Schneider, R. Shutt, P. Thompson, P. Wanderer and E. Willen Summary: Four of the initial six 17m long demonstration dipole magnets for the proposed Superconducting Super Collider have been constructed, and the first one is now being tested. This paper describes the magnet design and construction of the cold mass assembly. The magnets are cold iron (and cold bore) 1-in-1 dipoles, wound with partially keystoned current density-graded high homogeneity NbTi cable in a two-layer cos /spl theta/ coil of 40 mm inner diameter. The magnetic length is 16.6 m. The coil is prestressed by 15 mm wide stainless steel collars, and mounted in a circular, split iron yoke of 267 mm outer diameter, supported by a cylindrical yoke (and helium) containment vessel of stainless steel. The magnet bore tube assembly incorporates superconducting sextupole trim coils produced by an industrial, automatic process akin to printed circuit fabrication.         Development of a 40 mm bore magnet cross section with high field uniformity for the 6.6T SSC dipole    S. Caspi, W. Gilbert, M. Helm, L. Laslett and C. Taylor Summary: The SSC requires a very uniform dipole field. A 40 mm bore diameter winding cross section has been developed which has computed multipole coefficients less than 1x10/sup -6/of the dipole field at 10 mm radius for an operating field of 6.6T at 4.35 K. This cross section has 4 conductor blocks (3 wedges, 16 turns) per quadrant in the inner layer, and two blocks (1 wedge, 20 turns) in the outer layer. "Partially keystoned" cable is used; the inner cable has 23 strands of .0318 inch diameter wire; the outer cable has 30 strands of .0255 inch diameter wire. Model magnets have been constructed and the fields measured at room temperature and at liquid helium temperature up to fields exceeding 6.6T. Measured fields are compared to the predicted field. In addition, the as-built conductor positions in several magnets have been determined after cutting up the magnets. The predictions based on as-built configurations are computed and compared to measurements.         Design and testing of superferric magnets for accelerators    F. Huson Summary: The Texas Accelerator Center has designed, constructed and tested 26 accelerator magnets. The magnets are 3 tesla superferric magnets. Three currents are used to fix the dipole field and zero the sextupole and decapole. High quality magnets, which are simple and inexpensive, are obtained. Three 28 meter magnets have been constructed in industry as well as five 1 meter magnets.         1.8 K conditioning (non-quench training) of model SSC dipoles    W. Gilbert and W. Hassenzahl Summary: The accepted hypothesis is that training quenches are caused by heat generation when conductors move under Lorentz force. Afterwards no conductor motion will occur until a higher field and greater Lorentz force acts. If superior heat transfer and/or greater temperature margin is provided by operating at lower bath temperature, one might expect that the heat generated by conductor motion will not cause a runaway temperature increase, or quench. To test this hypothesis, the central dipole field in SSC model magnets was ramped at 1.8 K to 7.1 tesla without the magnets' quenching. The bath was then raised to 4.4 K and the magnets quenched at their short sample limits of 6.6 tesla or higher. Comparison with similar magnets trained in He I at 4.4 K is made and the significance of the nonquench training on system operation is discussed.         Cold yoke dipole magnets for HERA    K. Balewski, D. Degele, G. Horlitz, H. Kaiser, H. Lierl, K.-H. Mess, S. Wolff, C.-H. Dustmann, P. Schmuser and B. Wiik Summary: The proton storage ring of HERA will be equipped with a novel type of superconducting dipole magnet, combining an aluminum-collared coil with a cold iron yoke. The magnet features good field homogeneity, high quench currents, a low heat load on the cryogenic system and the possibility of a passive quench protection system. The magnet is described and test results are presented.         Excitation of a superconducting large thin solenoid magnet    M. Wake, M. Sakuda, T. Matsui, N. Ishihara, K. Maehata, Y. Doi, K. Ishibashi, T. Satow and H. Hirabayashi Summary: A superconducting large thin solenoid magnet was contructed for the VENUS detector in the TRISTAN 30 GeV e+ e- collider. The magnet has a 3.4 m warm bore diameter and a 5.24 m usable length with a material thickness of 0.52 radiation length. The first excitation was successfully performed up to 4000 A with no quench. Several forced quenches using a heater mounted on the coil were made to check the safety of operation. The quench propagation velocity was clearly measured in these quenches. The "quench back" phenomenon was observed about one second after the shut off of the power supply. The field quality of the magnet was found to be uniform within an accuracy of 0.3 per cent. The success of the first excitation was immediately followed by the assembly of the detector. VENUS was rolled into the TRISTAN collider storage ring and is now prepared for the first collision of e+ and e-.         ASTROMAG: A superconducting particle astrophysics magnet facility for the space station    M. Green, G. Smoot, R. Golden, M. Israel, R. Kephart, R. Niemann, R. Mewalt, J. Ormes, P. Spillantini and M. Wiedenbeck Summary: This paper describes a superconducting magnet system which is the heart of a particle astrophysics facility to be mounted on a portion of the proposed NASA space station. This facility will complete the studies done by the electromagnetic observatories now under development and construction by NASA. The paper outlines the selection process of the type of magnet to be used to analyze the energy and momentum of charged particles from deep space. The ASTROMAG superconducting magnet must meet all the criteria for a shuttle launch and landing, and it must meet safety standards for use in or near a manned environment such as the space station. The magnet facility must have a particle gathering aperture of at least 1 square meter steradian and the facility should be capable of resolving heavy nuclei with a total energy of 10 Tev or more.         A technique for epoxy free winding and assembly of COS /spl Theta/ coils for accelerator magnets    J. Carson and R. Bossert Summary: Traditional methods of magnet construction (wet winding) use molded coil subassemblies bonded together with epoxy impregnated fiberglass tape. This is a highly labor intensive process involving redundant operations for each of the four coils. The epoxy free winding technique (dry winding) eliminates the epoxy curing steps and also allows all four coils to be wound on a common winding mandrel, thereby reducing winding stations and handling. The tooling required for dry winding is a radical departure from existing technology imposing new mechanical problems. A number of 64 cm long 5 cm aperture SSC Design "B" magnets have been produced at Fermilab utilizing dry winding techniques. Discussed is the specialized tooling created to accomplish dry winding as well as new winding and assembly procedures required. Also discussed are mechanical problems encountered and their solutions. Based on experience gained, dry winding can be a viable, lower- cost alternative to traditional coil fabrication techniques.         Progress in the development of SIS quasiparticle mixers    P. Richards Summary: A summary is presented of recent SIS quasiparticle heterodyne mixer work done at Berkeley. Developments related to millimeter wavelength waveguide mixers include techniques for accurate measurements of noise and gain, integrated RF matching elements for large instantaneous bandwidths, large scaled modeling experiments, new W-band mixers with wide tuning bandwidth and only one mechanical adjustment, observation of very large coupled gain, systematic studies of the properties of array mixers, analysis of the effect of saturation on mixer measurements, very low noise in mixers with high quality junctions, and computer modeling to test the quantum theory of mixing. Developments related to planar lithographed mixers with quasi-optical antennas include construction of test apparatus, large scale modeling, and the design and evaluation of mixers which use RF matching structures integrated with bow tie antennas.         Saturation of the SIS direct detector and the SIS mixer    M. Feldman and L. D'Addario Summary: We review and discuss the theory of SIS direct detector saturation, and present experimental results which verify the theory, using N=2 and 4 SIS junctions in series. The measured responsivity is greater than the quantum limit e/Nh/spl omega/. This is not understood, We derive an explicit formula for the saturation of the SIS mixer and compare this to the direct detector.         SUBMM mixing experiments with planar Josephson junction devices    R. Panhuyzen, G.T. Horst, Th. De Graauw, H. Schaeffer, T. Klapwijk, J. Kortland and J. Mooij Summary: Planar Nb-Nb Josephson Junctions (JJ's) have been developed to be used in submillimeter heterodyne mixers. Experimental mixing results show a System Noise Temperature around 1000 K with a best result of 800 K at an operating temperature of 1.5 K. Preliminary results at 900 GHz are reported. A strong temperature dependence of the mixer noise temperature has been observed.         A 100 GHz SIS mixer of Nb/Al-AlO/sub x//Nb junctions    J. Inatani, T. Kasuga, A. Sakamoto, H. Iwashita and S. Kodaira Summary: We have made an all-refractory SIS mixer with four Nb/Al-AlO/sub x//Nb junctions connected in series. The mixer is designed to operate at 80-120 GHz. The area of each junction is 2.5 X 2.5 /spl mu/m/sup 2/. Both these SIS junctions and a mm-wave choke filter are fabricated on a crystalline quartz substrate. These Nb/Al-AlO/sub x//Nb junctions have shown ideal dc-characteristics and clear photon-assisted tunneling steps. RF measurements were made with a mixer mount which had two mechanical tuners. The conversion loss was less than 9 dB for 75-95 GHz. The minimum value was 8 dB. This value will be drastically improved by optimizing the normal resistance of the SIS junctions.         Chaos and bifurcation in Josephson voltage-controlled oscillators    A. Smith, R. Sandell, A. Silver and J. Burch Summary: We report the performance of a Josephson Voltage-controlled oscillator consisting of a tunnel junction shunted by a small inductor in series with a small bias resistor (a resistive SQUID circuit). The circuit displayed regions of stability, bifurcation, and chaos as a function of bias conditions and circuit parameters. We measured narrow band coupled power levels of 25 pW in the fundamental mode and 50 pW in the first subharmonic mode over a 10% frequency band at approximately 9 GHz. Linewidths were dominated by the thermal noise of the bias resistor. These results are in qualitative agreement with numerical simulations, which also show progressive bifurcations from fundamental to chaotic trajectories.         Coupled tunnel junction experiments at the gap frequency    R. Robertazzi, B. Hunt and R. Buhrman Summary: By using a capacitively coupled set of Josephson tunnel junctions we have performed experiments on the feasibility of using a Josephson junction as a local oscillator at frequencies up to and in excess of the gap sum of the junction. One junction was biased to serve as a local oscillator, whose AC power output could be monitored by observing the constant voltage Josephson steps on the current-voltage characteristic of the second junction. Using this coupling scheme we have coupled large oscillator signal levels (/spl sim/ 12.5nW) into the detector junction. For frequencies below the gap sum frequency our measurements are consistent with the Werthamer theory. For bias voltages above the gap sum we observe an anomalously fast roll off of the detected power from the oscillator junction.         A microwave operated fast superconducting switch    M. Muck, H. Rogalla and C. Heiden Summary: A superconducting switch was constructed and tested based on the microwave induced transition of a microbridge or long filament into the resistive flux-flow state. Resistance values of the order of 1 k/spl Omega/ were obtained by connecting in series several microbridges, made of thin films of refractory materials like Nb or Nb/sub 3/Ge. Due to low power consumption and a lack of electromagnetic interference when used with suitable filters, such switches appear to be well suited in connection with superconducting electronics, incorporating for instance SQUIDs. Results on switching speed, power consumption and crosstalk between the switch and other circuit components located on the same chip are investigated.         Experimental considerations in the quest for a thin-film superconducting field-effect transistor    A. Hebard, A. Fiory and R. Eick Summary: Trilayer structures, comprising a thin-film In/InO/sub x/superconductor separated from an Al gate electrode by an overgrown dielectric, have been studied to ascertain the feasibility of electric-field control of superconductivity for device applications, Modulation of the areal charge density of 50-/spl Aring/ thick In/InO/sub x/films has been found to cause more than a 350/spl Omega///spl square/change in the sheet resistance near the midpoint of the resistive transition in one film and the creation of ~10/spl Omega///spl square/of resistance from the superconducting state of a second film. We report on efforts to increase this modulation by decreasing the electron density of unperturbed films, improving the charge storage capabilities of the thin-film gate dielectrics, and improving the carrier mobility which has been found to be sensitive to interface preparation. Device implications, based on these results, are also discussed.         Millimeterwave emission from Josephson oscillator through thin film junction electrode    K. Yoshida, T. Nagatsuma, S. Kumataka and K. Enpuku Summary: An experiment on the coupling of the flux-flow type Josephson oscillator to SIS detectors by inductive coupling scheme has been carried out. Radiated powers from the Josephson oscillator were detected by an array of Josephson tunnel junctions fabricated on top of the upper electrode of the oscillator. The thickness of the common electrode was made thin enough to allow inductive coupling through the electrode. The maximum value of the obtained voltage amplitude of the emitted wave from the oscillator was 1.7mV, which is in reasonable agreement with the theoretical one. The present method can be an efficient coupling scheme between the Josephson oscillator and external circuits.         MRI-superconductivity in the marketplace    R. Schwall Summary: Magnets for medical Magnetic Resonance Imaging (MRI) represent the first large scale commercial application of superconductivity. These devices have been in production in the U.S., the U.K., and Europe for several years and the basic designs have stabilized. Since the magnets operate at relatively low fields (generally < 2 Tesla), they have not required advances in basic superconducting materials or magnet technology. Progress has come rather in the areas of cryogen consumption, field homogeneity, transportability, shielding, reliability, and the user interface. This paper reviews the currently available devices and the areas presently under development.         Superconducting magnets for magnetic resonance imaging applications    G. Morrow and C. Rosner Summary: Recent applications of one-meter bore Superconducting magnets to allow imaging of human brain tissue, the central nervous system, the spine and other internal organs by utilizing the phenomenon of nuclear magnetic resonance (NMR) have resulted in a revolutionary development in medical diagnostics and a unique application of superconductive technology in medicine. At present, S/C magnets are most frequently utilized in MRI systems because they can most effectively produce the highly uniform, stable, and powerful field required for the imaging process. Although it has been demonstrated that quite acceptable image quality can be obtained at virtually any magnetic field strength, from 0.3 Tesla through 2.0 Tesla, the question of optimum central field for MR Imaging and Spectroscopy is still open. Since S/C magnets offer the widest range of field strengths, they are helping to contribute to the collection of clinical data which will eventually clarify the question of optimum central field for Magnetic Resonance diagnostic applications. In addition, S/C magnets have contributed to the successful application of MRI in mobile, or truck-based systems, with operating data on S/C magnets showing high magnet system availability in actual clinical mobile use. This data will be reviewed as will the design considerations of the S/C MRI magnet cryostat and cryogen recondensers, particularly as they relate to reliability, uptime, and system level interactions with the imaging hardware and software.         A 4.7 tesla magnet for magnetic resonance imaging and spectroscopy    M. Green and J. Carolan Summary: This paper describes the design of a superconducting MRI magnet for imaging experimental animals. The magnet is designed to have an 0.5 m warm bore with a central induction of 4.7 tesla. The field uniformity will be good enough to do NMR spectroscopy on living animals as well as magnetic resonance imaging. The magnet is designed so that the field will be less than 0.1 tesla at the cryostat outside boundary and the 0.0001 tesla (1 gauss) line will be about 5 meters from the center of the magnet when the central magnetic induction is 4.7 tesla.         A 60 cm bore 2.0 tesla high homogeneity magnet for magnetic resonance imaging    E. Bobrov, R. Pillsbury, W. Punchard, R. Schwall, H. Segal, J. Williams and L. Neuringer Summary: A 60 cm warm bore imaging and spectroscopy magnet has been constructed and placed in operation at the Francis Bitter National Magnet Laboratory (FBNML). The magnet achieved its design central field of 2.0 T but is currently being operated at 1.5 T. It operates in the persistent mode with a measured decay rate of less than 0.03 ppm/hr. Employment of both 10 superconducting shims and small ferromagnetic shims located close to the warm bore has resulted in a homogencity of better than 3 ppm throughout the 25 cm diameter spherical volume (DSV). Room temperature shim coils have not been incorporated into the system. A novel form of compact shielded pulsed gradient coil system has been designed, constructed and tested. In such a system, appropriate configuration of an external shield coil results in cancellation of external flux without the introduction of impurity harmonics that degrade the linearity of the gradients. Six sets (X, Y, Z coils, and X, Y, Z shields) have been incorporated into a unit of 6 cm build. The all aluminum cryostat employs a 77 K nitrogen recondenser and a shield cooler operating at less than 20 K. Steady state helium consumption is about 50 ml/hour. The system is currently being used for both high resolution, in-vivo/sup 31/P-NMR spectroscopy and a variety of MRI experiments including/sup 23/Na imaging of eyes.         Considerations in the design of MRI magnets with reduced stray fields    D. Hawksworth, I. McDougall, J. Bird and D. Black Summary: One of the major considerations in siting choice for an MRI system within a hospital is its interactions with its environment. This interaction places restrictions on the proximity of equipment sensitive to magnetic field and limits areas of general public access. In addition special account must be taken of the possible impact of environmental iron on magnet homogeneity. To date, the approach adopted by the MRI system scanner manufacturers to these problems has been to employ either YOKE or MIRROR iron (PASSIVE) shielding frequently requiring significant structural modifications with associated costs. An alternative approach to the shielding problem has been investigated at OXFORD using a geometry utilising superconducting counter running coils alone and prototypes with Central fields of 0.5T, 1.0T and 1.5T have been tested.         Superconducting magnetometer system for detecting lung contaminants    D. Paulson, R. Toussaint, R. Fagaly and S. Robinson Summary: We describe a superconducting magnetometer system for the detection and measurement of ferrimagnetic contaminants or tracer materials in the lungs. This technique, known as magnetopneumography (MPG), offers a non-invasive, passive means to investigate lung clearance mechanisms using inhaled biologically inert magnetic tracers or to measure some potentially toxic air-borne particulates due to environmental or occupational sources. The MPG system consists of two principal components, a SQUID magnetometer and a superconducting magnet, each with its own liquid helium dewar. The response of the system is a function of both the magnetizing field and the field sensitivity of the SQUID detection coils. The SQUID magnetometer has a sensitivity of less than 700 fT (1 fT = 10/sup -15/Tesla). The equivalent system noise in terms of particulate contaminants is less than one microgram of total ferrimagnetic particulates dispersed uniformly throughout in the lungs. The MPG system described has an order of magnitude better sensitivity than any previously constructed system, and has the ability to detect relaxation phenomena with time constants as short as 10 seconds. This is expected to assist in the understanding of lung clearance mechanisms.         The positioning problem in biomagnetic measurements: A solution for arrays of superconducting sensors    S. Erne, L. Narici, V. Pizzella and G. Romani Summary: We propose a system to measure automatically the location of the subject's head in the reference frame identified by an array of superconducting biomagnetic sensors (the same procedure may be employed for Cardiac studies with little or no modification). The system consists of small reference coils (magnetic dipoles) to be properly positioned on the subject's head. The coils are driven by a known current signal. The generated magnetic fields are measured by the superconducting array and decoded by a suitable algorhythm which calculates the relative position of the coils with respect to the array itself. In this paper we present a schematic of the system. The results of a computer simulation, carried out for different types of superconducting detection coils are also illustrated.         Design advances in superconducting magnetic energy storage for electric utility load leveling    R. Loyd, S. Schoenung, T. Nakamura, W. Hassenzahl, J. Rogers, J. Purcell, D. Lieurance and M. Hilal Summary: Superconducting Magnetic Energy Storage (SMES) has been under study for electric utility energy storage application since the early 1970's. Major challenges have included structural design to accommodate large biaxial loads over a long lifetime, design of a conductor to carry high current, design of a reliable and passive coil protection system, design for conventional fabrication and construction methods, and system cost reduction. A SMES design concept, developed by the authors of this paper, includes technically feasible solutions to all the items listed above. Plans for full development and commercialization of this technology are being prepared.         Lightweight magnet for space applications    E. Leung, M. Hilal, J. Parmer and S. Peck Summary: The use of cryogenic and superconducting magnets in space is being investigated for pulsed power generation, power conditioning and energy storage and could play a major role in the Strategic Defense Initative (SDI) program. Potential space magnet applications, current technological limits and areas where additional development is required have been identified. A short history of superconducting magnets in space is included. Technology study results, including consideration of zero-gravity conditions for magnet cooling, space-based refrigerator/liquefiers, advanced composites to reduce magnet weight and structures that satisfy launch and space environmental requirements are presented. Computer programs have been developed to optimize spaceborne magnet system weight with respect to the power supply, magnet operating current density, cooling scenario, charge and discharge rates, load characteristics and magnet configuration. Ground-based magnets built to date have stored energy to mass ratios (specific energies) of less than 3 J/gm ; it is expected that space-based magnets with specific energies of more than 50 J/gm can be designed and built in the near future.         The experimental study of protection method of large superconducting coil systems    T. Shintomi, K. Otani, M. Masuda, G. Cha and Y. Kwon Summary: The present work is to obtain a useful method overcome such difficulties in a protection of the superconducting coil of SMES. The idea of the protection method is proposed and the technological difficulties in realization of such idea have been investigated by experiments using a 60 kJ superconducting coil.         Transient performances of the 20 kVA superconducting synchronous generator in power systems    T. Okada, T. Nitta and T. Shintani Summary: This paper describes the electrical transient performance of the experimental superconducting synchronous generator. The generator is connected to a regional power system through two artificial transmission lines in parallel. Several experiments to make clear the transient behavior of the SCG in the power system have been performed. The experiment items are as follows; (1) Steady state stability test by a quasi-stationary increase of the generator output. (2) Disconnecting and reclosing of either line of the transmission lines in parallel. (3) Three-phase grounding fault at the midpoint of the transmission line with reclosing after clearing the fault. (4) Transient stability test by three phase grounding fault with reclosing after clearing the fault. The variations of the terminal voltage, the armature current and the output power of the SCG for these tests have been measured and discussed. In order to understand the transient behavior of SCG's, the transient analysis by a computer simulation was carried out for the experiments. The simulation results are in good agreement with the experimental results. By use of the simulation results, we calculate the torque and the Joule heating of the cold and the warm dampers for the transient state.         Geometric considerations in the design and fabrication of multifilamentary superconducting composites    T. Kreilick, E. Gregory and J. Wong Summary: Design characteristics of the superconducting strand to be used in the manufacture of dipole magnets for the Superconducting Super-Collider (SSC) have not yet been fully established. Ideally, the configuration chosen will minimize field distortion at low fields where injection takes place. The paper presented here will discuss the advantages of the "single stack" method of wire manufacture for this application. Various techniques for assembling the large numbers of filaments required are discussed. The utilization of hexagonal and round sub-elements, as well as the introduction of a woven wire mesh, are highlighted. A discussion of the uniformity of filament arrays, filament spacing, and the role these play in the attainment of high current density material is included.         Characterization of vanadium diffusion barriers in Nb-Sn composite wires    D. Smathers, P. O'Laray, M. Shiddall, J. Peterson and Wm. McDonald Summary: Ductile vanadium has been explored for use as a diffusion barrier material in niobium-tin composite wires. Vanadium is found to co-process well, standing over 99.995% area reduction without anneal. Resistance ratios greater than 300 to 1 (0/spl deg/c to 20K) have been measured in reacted composite wire with noncopper current densities greater than 1700 A/mm/sup 2/at 10 Tesla, 4.2K. Vanadium forms an intermetallic compound on the tin side which should not be superconducting above 4.2K. The composite residual resistance ratio (RRR) is seen to be dependent on reaction conditions being higher as the reaction temperature is dropped. To determine the source of this effect a copper-vanadium composite was fabricated. Features similar to the superconducting wire were observed. There is a reasonable overlap of reaction conditions suitable for both the superconductor and the copper making high RRR possible for optimized conductors.         Prototype fabrication of ultrafine filament NbTi conductors for the SSC    C. King, K. Hemachalam, B. Zeitlin and R. Scanlan Summary: Production quantities of multifilamentary NbTi/Cu composite wire have been fabricated for SSC dipole magnet development. These composites contained 10,000 to 37,000 filaments having a diameter of 5.0 to 2.7 micrometers at final wire size. The large number of filaments in these composites has been achieved by employing a double extrusion process. The critical current density (Jc) has been optimized for the final wires as well as for samples taken from the first stage extrusion. Jc ranged from 2300 to 3400 A/mm/sup 2/at 5 tesla depending on filament size and process history. The Jc results obtained in this investigation along with resistive transition parameter "n" are reported.         Development of Nb/sub 3/Sn superconducting wires for AC use    K. Yamafuji, M. Iwakuma, Y. Tomita, K. Funaki, F. Sumiyoshi, T. Fukutsuka, R. Ogawa, T. Miyataka and K. Matsumoto Summary: We have fabricated the powder-metallurgy (P/M) processed Nb/sub 3/Sn superconducting wires as the first trial for the development of P/M processed Nb/sub 3/Sn wires for AC use. The Nb content was chosen as small as 22.5wt% so as to avoid the appearance of interfilamentary coupling inside the wire. Nevertheless, the smallest effective diameter d/sub eff/obtained in the present trial was 37/spl mu/m, while the average diameter of Nb/sub 3/Sn filaments was 1/spl mu/m. The Critical current density Jc of filamentary region was 1.7x10/sup 9/A/m/sup 2/at 4.2K at 1T. A test coil with the coil length of 160mm, inner diameter of 34mm and outer diameter of 146.5mm was wound by a (3X7)- strand cable of P/M processed Nb/sub 3/Sn wires in the wind and react method, and a pulse-mode operation was carried out. We have also fabricated the external diffusion (E/D) processed Nb/sub 3/Sn multifilamentary wires to seek for another possibility for the development of Nb/sub 3/Sn superconducting wires for AC uses. The wire diameter was 0.15mm, the filament diameter was 0.5/spl mu/m, the number of filaments was 17935, and the twist pitch was 1mm. The overall critical current density was 1.8x10/sup 9/A/m/sup 2/at 4.2K and 2T, which is about 3 times larger than that of the corresponding NbTi multifilamentary wires. A test coil with the coil length of 50mm, inner diameter of 20mm and outer diameter 30.4mm was also wound by 3-strand cable of E/D processed Nb/sub 3/Sn wires in the wind and react method, and 60Hz operation was carried out. The present trial indicates that the superior characteristics of Nb/sub 3/Sn wires such as high temperature margin and large amplitude availability compared with NbTi wires could be the additional advantageous characteristics of further developed Nb/sub 3/Sn wires for AC uses.         Development of a Nb/sub 3/Sn composite conductor with very fine filaments and basic studies on its power frequency applications    Y. Kubota and T. Ogasawara Summary: A Nb/sub 3/Sn composite conductor with about 10 thousands filaments has been manufactured by the external diffusion process. Fine filament size of 0.36 /spl mu/m (design value), a tight twist pitch of 0.61 mm for the wire diameter of 0.103 mm and bronze matrix resulted in a strongly reduced a.c. losses: the hysteresis loss and the coupling current loss were observed to be 500 kW/m/sup 3/and 30 kW/m/sup 3/respectively in the a.c. field of 50 Hz with an amplitude of 2.0 T. A triplex conductor was constructed by cabling three strands and a small Coil was wound from this cable. In the d.c. mode operation, the coil generated a field of 1.8 T at the critical current I/sub c/= 28 A. In 50 Hz operation the coil was able to be operated up to the static critical current I/sub c/. At this critical condition, the observed a.c. loss averaged over the windings was 450 kW/m/sup 3/.         Calorimetric measurement of AC loss in ICCS conductors subjected to pulsed magnetic fields    J. Minervini, M. Steeves and M. Hoenig Summary: A calorimetric apparatus was developed to measure the AC loss in internally-cooled cabled superconductors (ICCS) which were subjected to pulsed magnetic fields. The purpose of the measurement was to compare the losses of several superconducting wires being considered for use in ohmic heating coils for tokamak fusion devices. The apparatus consisted of a vacuum chamber containing two samples of ICCS, and a pulse coil set surrounded by a Bitter magnet which provided a steady background field. First, the composite enthalpies of the samples were determined, and then the response of each sample to pulsed fields was recorded. A plot of energy versus pulse rate was then constructed. Results are presented for several types of Nb/sub 3/Sn wires (bronze process, internal tin, and jelly roll) at a 10 tesla background field and for pulse rates up to 150 tesla/second.         Transport mechanisms in a microparticle conductor    M. Ashkin and M. Beasley Summary: Transport properties of the microparticle superconductor described in the companion paper are represented by a percolative network of Josephson-coupled particles. Microparticle composite wires that have the best critical currents have resistivity ratios >1, suggesting that metallic conduction dominates and coupling occurs via weak links. The experimental j/sub c/is proportional to 1//spl rho/eff, where 1//spl rho/eff is the effective normal resistivity, in a qualitative analogy to a published relation calculated for a 3D percolative superconductor. The upper limit to j/sub c/is estimated taking into account percolation and flux pinning. Using an approximate theory for a percolative network this upper limit is expected to be j/sub c/ /spl siml/ 0.05 J/sub max/, where j/sub max/ is the critical current density in a perfect lattice of dirty weak links.         Superconducting microparticle composite wire    A. Braginski and A. Male Summary: A novel concept of a ductile composite wire which incorporates filaments made of brittle superconductor powders was proposed and experimentally demonstrated. Unsintered, submicron NbC powders were encapsulated in copper tubes. These were fabricated down to single filament wires without sintering or high temperature annealing. Multifilamentary composites with up to 3000 filaments were then formed by successive rebundling of tubes into sealed billets and their mechanical reduction. Due to the fluid-like behavior of the unsintered powder core, the composites were ductile and resistant to filament fracture. The wire critical temperature was 10 to 11 K, the upper critical field was 2 /spl plusmn/ 0.2 tesla and the superconductor self-field critical current density attained 6x10/sup 8/amps/m/sup 2/. The critical current showed a remarkable tolerance of uniaxial and bending strains. While the NbC superconductor is not of great technical interest, it permitted one to prove the new concept. The subsequent use of NbCN powders confirmed that the observed wire behavior is also obtained in high magnetic fields, up to 15 tesla.         Study of layered and coevaporated V(Mo)N and (V/Si)N films    G. Gibson, J. Moodera, P. Tedrow and R. Meservey Summary: Layered and coevaporated V/Mo samples were nitrided and their T/sub c/'s and spin-orbit scattering rates were compared. This is of Interest because of the close lattice match of VN with the postulated high T/sub c/of cubic MoN. In no case was a T/sub c/higher than that of VN obtained. The spin-orbit scattering rate was found to be larger in the layered (V/Mo)N samples than in the coevaporated ones. We have compared (V/Mo)N and similarly made (V/Si)N multilayer films with theories for the critical field of such structures. Evidence for dimensional crossover was seen in the parallel critical field curve of (V/Mo)N films. Also, the T/sub c/of thin (V/Si)N multilayers was found to be dependent on the Si layer thickness.         Angle resolved XPS studies of oxides at Nb-, NbN-, NbC- and Nb/sub 3/Sn-surfaces    J. Halbritter and A. Darlinski Summary: Nb, NbN, NbC and Nb/sub 3/Sn are known to be chemically inert with passivating oxides only solvable in HF-acid. Despite Nb/sub 2/O/sub 2/as outermost oxide layer, the oxides of Nb compounds show large differences in thicknesses and in electronic properties. To quantify the differences, angle resolved XPS (ARXPS) measurements have been performed. The simultaneous fitting for different angles and preparations of the Nb, Sn, C, N and O XPS lines of the oxides yielded the following stoichiometries and distributions : a) Nb/sub 2/O/sub 2/is the outermost oxide layer on all Nb-compounds. In the case of Nb/sub 3/Sn the SnO/sub 2/is substituted throughout the Nb lattice ((Nb/sub 2/O/sub .5/)/sub 1.5/SnO/sub 2/), whereas for NbN the N substitutes O sites in Nb/sub 2/O/sub 2/(Nb/sub 2/N/sub 2-x/O/sub 3+x/,x /spl lsim/1) adjacent to NbN in air oxidation. b) For Nb and Nb/sub 3/Sn underneath Nb/sub 2/O/sub 2/the NbO matches to the metallic suboxides. c) NbX/sub 1-x/O/sub x/(x<0.5) as metallic suboxide forming lumps. The oxide growth a-c is not planar, instead the oxides serrate the metal surface on a nm scale. The serration is strongest for soft, defective Nb and smallest for the harder compounds NbN and NbC in Parallel to the oxidation rate which is slowest for NbC. This first identification of the oxinitrides of the metallic suboxides and of the reduced serration of NbN (NbC) explains the improved oxide quality and quality of tunnel junctions and rf cavities as compared to defective Nb single cristals. The first identification of NbX/sub 1-x/O/sub x/(x<0.5) compounds serrating the metals explains many deteriorations of superconductivity by oxidation. In granular NbN metallic and dielectric oxides have been identified between the grains.         Josephson junctions coupled by an ion-implanted vertical semiconductor membrane    X. Wu, D. Chin and T. Van Duzer Summary: Superconducting devices with two niobium electrodes separated by a vertical silicon membrane have been fabricated. The silicon membrane typically of 100-300 nm thickness, is degenerately doped by arsenic ion implantation and capped by a thin layer of silicon dioxide. The small dimensions of the membrane are achieved by photolithography and controlled isotropic wet etching followed by CBrF/sub 3/reactive ion etching. The electrodes of 200 nm thickness are formed by sputter deposition and photolithographic patterning. The metal film on top of the membrane is removed using a photoresist planarization technique, followed by CF/sub 4/reactive ion etching. A typical device with a 300 nm-thick barrier and with 50 /spl mu/m-wide electrodes displays Josephson junction characteristics with a critical current of about 8 /spl mu/A at 4.2 K. The observed product of critical current and normal resistance is in the range of 0.4-0.8 mV at 4.2 K among the devices tested.         PECVD SiO/sub 2/ film as a junction isolation for all refractory Josephson IC    S. Kosaka, A. Shoji, M. Aoyagi, Y. Sakamoto, F. Shinoki and H. Hayakawa Summary: Preparation of SiO/sub 2/films by using plasma-enhanced chemical vapor-deposition (PECVD) were investigated in order to obtain insulating layers which are applicable to large scale Josephson integrated circuits with high reliability and high production yield. Defect densities of the deposited films were estimated by measuring dielectric breakdown strength distribution of the films and found to be less than 0.5/cm/sup 2/in films of thickness 100-1000nm range, which is acceptable for the use to Josephson IC with LSI level complexity. The PECVD SiO/sub 2/films are successfully applied to an integration of all refractory Josephson IC.         Nature of coupling and dimensional crossover in superconducting multilayers    J. Locquet, W. Sevenhans, Y. Bruynseraede, H. Homma and I. Schuller Summary: A comparison of the temperature dependent upper critical fields in Josephson and proximity coupled multilayers is presented. The results are in good agreement with theoretical expectations which predict that the main determining factor is the spatial variation of the electronic density of states.         A laser quenched superconducting switch for pulsed power applications    T. Francavilla, D. Peebles, H. Nelson, J. Claassen, S. Wolf and D. Gubser Summary: We have prepared micron thick films of NSN and NbCN by rf reactive sputtering. Sputtering conditions were varied in order to maximize the critical current density and the normal state resistivity. Both of these quantities are important for a normally closed switch in parallel with a load. The product of these two quantities is a figure of merit used to compare films prepared under different conditions. By varying substrate temperature, argon pressure and adding small amounts of oxygen to the reactive gas mixture, we have achieved a value of 900 V/cm. In addition we have fabricated some of these films into a laser activated switch which opens and recovers in times on the order of nanoseconds.         Optimal design of high current superconducting switches and the feasibility of their testing    M. Rizkalla and S. Mahil Summary: We have designed a superconducting switch for optimum heat transfer from a high current carrying superconducting thin film to the substrate. This design is based upon the acoustical matching of the different layers of the compound substrate. The switch-recovery time is considered to be of the order of 1 /spl mu/sec. The design of a magnetic triggering circuit that generate high current field (of approximately 1500 A/cm) pulses of 1 /spl mu/sec duration has also been demonstrated. A simple LC circuit is employed to generate high current oscillations of 0.25 MHZ frequency. The optimum parameters of this circuit have been computed.         RF surface resistance of Nb/sub 3/Sn, NbZr, and NbN thin films    L. Allen, M. Beasley, R. Hammond and J. Turneaure Summary: The surface resistance of Nb/sub 3/Sn films prepared by electron-beam co-deposition and magnetron sputtering has been measured at 8.6 GHz and from 1.5 K through T/sub c/. We find that carefully controlled deposition temperatures of /spl ap/900 C are necessary to obtain the lowest-loss materials. In both evaporated and sputtered samples with stoichiometric composition (T/sub c/= 17.8 K), we see sharp transitions. In off-stoichiometric samples, however, the transition is lower and wider, yielding excessive losses. The residual losses, normal-state surface resistance, and the reduced gap values we obtain for our Nb/sub 3/Sn samples are also discussed. The surface resistance of a NbZr alloy film and a NbN sample obtained from Hypres, Inc. are also reported.         Energy loss, anisotropy, magnetoresistivity and recovery in aluminum strained at 4.2 K    K. Hartwig and G. Yuan Summary: High purity aluminum is often considered and sometimes used as the stabilizing material for practical composite superconductors. Such material has a residual resistivity ratio (RRR = \partial273K/\partial4.2K) in the range 1000 - 5000 when fully annealed. An understanding of how the RRR will change during conductor use is necessary for optimum system design. We have investigated the effects of cyclic plastic strain at 4.2K and annealing to room temperature on the RRR and magnetoresistance of aluminum covering a wide purity range. Measurements of mechanical hysteresis energy loss, anisotropic resistivity and strain induced magnetoresistance are reported. We describe selected experiments and discuss the implications of results on conductor operation.         A superconducting modulator for extremely sensitive voltage measurements across multifilamentary superconducting wires    F. van Overbeeke, H. ten Kate and L. van de Klundert Summary: In this paper we describe a superconducting chopper amplifier used as an instrument to measure the V(I) curve of multifilamentary superconductors. Experimental results are presented.         Investigation of the surface resistance of superconducting niobium using thermometry in superfluid helium    P. Kneisel, G. Muller and C. Reece Summary: For future application in high energy linear colliders superconducting accelerator structures must exhibit gradients of at least E/sub acc/= 30 MV/m at Q-values above 10/sup 10/. Even though Q-values as high as 10/sup 11/have been obtained in smaller assemblies, the Q-value of niobium accelerator structures is usually limited by temperature independent residual losses. The corresponding average residual resistance is typically a few orders of magnitude higher than the theoretical surface resistance at 1.5 K predicted by the BCS-theory. In order to systematically investigate the spatial distribution of the residual resistance and its dependence on surface conditions of the niobium cavity surface, we have built a TE/sub 011/- S-band cavity and a thermometry system, which allows the detection of losses as low as a few microwatt in superfluid helium using a lock-in technique. The thermometry system consists of 100 Allen-Bradley carbon resistors, which are pressed against the endplate of the cavity and which are well shielded against the surrounding helium bath. A computerized data acquisition system is used to measure the loss distribution on the endplate of the cavity. First measurements indicate the presence of three kinds of losses: joint losses caused by poor rf contact at the indium gasket between cavity body and endplate, large patches of moderate resistance and a few localized spots of enhanced losses. With the present system we have been able to measure at a bath temperature of 1.5 K surface resistances of about 50 nOhm at an rf magnetic field of about 20 Oersted, which in turn indicates that at some higher field levels the system will be capable of detecting loss distributions equivalent to Q-values above 10/sup 11/.         Contactless method for magnetoresistivity measurements    A. Ricca and S. Zannella Summary: A method is described to measure, at the liquid helium temperature, the resistivity and magnetoresisti vity of cylindrical metal bars by means of magnetization techniques used for superconductor ac loss measurements. The specimen is exposed to a variable ramp-like magnetic field in the axial direction. By means of two pick-up coils the magnetization hysteresis loop associated with eddy currents is recorded. Since the magnetization M of the bar is inversely proportional to resistivity /spl rho/, the positive branch of the hysteresis loop also represents the dependance of 1//spl rho/ on H. The results obtained for OFHC and 99.999% purity copper agree with those reported in the literature.         Welding and brazing the westinghouse fusion magnet coil    R. Fetzko and T. Hordubay Summary: The magnet assembly required high quality welded and brazed construction. The quality standards were achieved by developing and testing of production procedures, training and qualification of craftsmen per the procedures, and in process monitoring, control, and non-destructive testing. Modification of standard production equipment and development of unique and specialized tools was necessary in order to repeatably obtain high quality welds and brazes. These procedures resulted in conductor joints that had a resistance of only 10/sup -9/ohms tested at 20 KA and 3 Tesla. The two hundred plus tube welds and approximately five hundred header welds collectively passed the required helium leak test with no detectable leaks.         Superconducting properties of powder metallurgy processed Nb/sub 3/Al wires    K. Watanabe, K. Noto and Y. Muto Summary: Powder metallurgy processed Nb/sub 3/Al wires with low areal reduction ratios of R = 8x10/sup 3/to 1x10/sup 4/have been investigated on superconducting properties. We have done the optimization of high field J/sub c/values for Nb-8 wt.%Al with different areal reduction ratios. T/sub c/was 17.1 K for the sample with a two stage heat treatment such as 1200/spl deg/C for 15 sec followed by 750/spl deg/C for 3 days in contrast to the low T/sub c/values below 16 K for the samples with a single heat treatment at 800/spl deg/C. B/sub c2/for a two stage heat treated sample increased about 5 T at 4.2 K in comparison with a single heat treated sample. The measured B/sub c2/values were well fitted to the theoretical curve of the upper critical field. The overall J/sub c/values were measured up to 23 T at 4.2 K and J/sub c/= 10/sup 4/A/cm/sup 2/at 17.5 T was achieved.         Formation of Nb/sub 3/Al in Nb-Al superconductors by powder process    P. Johnson, Y. Im, L. McKnelly and J. Morris Jr. Summary: The critical current density of Nb-Al superconductors made by powder process is limited predominantly by the volume fraction and composition of the superconducting A15 phase (Nb/sub 3/Al). Reacted Nb-Al powder wires contain A15, sigma phase, and unreacted Nb. The Nb and Al particles in an unreacted wire draw down to thin sandwiched ribbons. The layers in the wire are not uniform. In some regions, Nb particles have agglomerated to form superlayers which limit the extent of A15 formation. In the reacted wire, continuous regions of A15 up to 1 /spl mu/m wide are seen in TEM. Other regions form layered arrangements of Nb/A15//spl sigma//A15/Nb. The presence and volume fraction of these phases can be understood in light of recent work on thin Nb/Al multilayers made by sputter deposition. To characterize the average Nb layer thickness in the unreacted wires, a Nb "drawing index" is defined as (Nb powder size)/(R)/sup 1/2/. The critical current density is found to scale well with this parameter for a wide range of wires. To decrease the agglomeration of Nb particles, a set of wires were made in which the loose Nb powders were precoated with Al by evaporation.         The properties of ZrN films and ZrN-based tunnel junctions    V. Pan, V. Komashko, E. Rudenko, Yu. Boguslavsky and R. Zelenkevich Summary: The results of investigation of the structure and physical properties of zirconium nitride films and tunnel junctions made of them are presented. Formation conditions of ZrN heteroepitaxial layers on sapphire substrates have been studied. Superconducting properties and resistivity of 23 to 240nm thickness films obtained on different substrates over deposition temperature range 450 to 1000/spl deg/C have been investigated. The energy gap in ZrN films has been determined from I-V characteristics of ZrN-I-Pb junctions taking into account the proximity effect.         Influence of pins on the dynamical mixed state in superconducting films    V. Pan, V. Prokhorov, G. Kaminsky and C. Tretiatchenko Summary: I-V dependences and their first-order derivatives have been investigated for inhomogenious Pb - 22 % Bi films. I-V curves of type II superconductors at dynamical mixed state are shown to have nonlinear behaviour due to the pinning. The theoretical description of the initial parts of I-V curves has been developed.         An aluminium stabilized conductor for the ALEPH solenoid    J. Le Bars, M. Humeau, A. Lameule, M. Locatelli, P. Nicolas and L. Sapin Summary: Continuous controls during the production and results of short sample tests are the subject of this report. The conductor, made of a Cu:Nb-Ti cable inside a pure aluminium matrix is obtained by a coextrusion process. A knowledge of the quality of bonding between these two parts was important an a set of controls using classical sample tests and new continuous controls has been developed at Saclay.         Construction and testing of the mirror fusion test facility magnets    T. Kozman, D. Shimer, J. VanSant and J. Zbasnik Summary: This paper describes the construction and testing of the Mirror Fusion Test Facility superconducting magnet set. Construction of the first Yin Yang magnet was started in 1978. And although this particular magnet was later modified, the final construction of these magnets was not completed until 1985. When completed these 42 magnets weighed over 1200 tonnes and had a maximum stored energy of approximately 1200 MJ at full field. Together with power supplies, controls and liquid nitrogen radiation shields the cost of the fabrication of this system was over $100M. General Dynamics/Convair Division was responsible for the system design and the fabrication of 20 of the magnets. This contract was the largest single procurement action at the Lawrence Livermore National Laboratory. During the PACE acceptance tests, the 26 major magnets were operated at full field for more than 24 hours while other MFTF subsystems were tested. From all of the data, the magnets operated to the performance specifications. For physics operation in the future, additional helium and nitrogen leak checking and repair will be necessary. In this report we will discuss the operation and testing of the MFTF Magnet System, the world's largest superconducting magnet set built to date. The topics covered include a schedule of the major events, summary of the fabrication work, summary of the installation work, summary of testing and test results, and lessons learned.         Temperature-dependent properties of niobium nitride Josephson tunnel junctions    A. Shoji, M. Aoyagi, S. Kosaka and F. Shinoki Summary: We report the electrical properties of all niobium nitride(NbN) Josephson tunnel junctions with magnesium oxide(MgO) films as barriers in the temperature range 4.2-15 K. NbN/MgO/NbN Josephson tunnel junctions have large gap voltages(V/sub g/=4.8-5.4 mV), large products of the maximum critical currents and the normal tunneling resistances(I/sub c/R/sub n/=3.15-3.35 mV), and small subgap leakage currents(V/sub m/=13-138 mV) at 4.2 K. The junction parameters decreased with increase in temperature, but reasonably large junction parameters(for example, V/sub g/=4.9 mV, I/sub c/R/sub n/=2.67 mV, and V/sub m/=22 mV) have been obtained even at 9 K. The magnetic penetration depth in NbN electrodes has been measured up to 15 K using two-junction interferometers which consist of NbN/MgO/NbN junctions, NbN ground planes, and NbN control lines.         Fabrication and characteristics of NbN-based Josephson junctions for logic LSI circuits    S. Yano, Y. Tarutani, H. Mori, H. Yamada, M. Hirano and U. Kawabe Summary: The characteristics of a 1.5 /spl mu/m square NbN-based Josephson junction were investigated and improved to make large scale application of these junctions to logic LSI circuits possible. An amorphous-like Si thin film was newly examined in order to define a junction area consistent with the pattern size of the resist mask. A Nb-oxide barrier was formed on a NbN base electrode by rf plasma cleaning and oxidation. The low leakage current (the characteristic voltage Vm, that corresponds to converting the leak into the maximum junction currents, being larger than 40 mV) and the small critical current variation were achieved by low rf-voltage plasma cleaning. By using Si-insulating layers and optimizing surface-cleaning conditions, the maximum critical current variation was reduced within /spl plusmn/12% for 850 junctions. The change in the normal tunneling resistance R/sub nn/due to heat-treating below 200/spl deg/C was kept within /spl plusmn/5%. To confirm the feasibility of applying the junctions to logic LSIs, a 3K-logic-gate array was fabricated using about 23,000 junctions and its operation was successfully demonstrated.         An all-niobium eight level process for small and medium scale applications    L. Yu, C. Berry, R. Drake, K. Li, R. Patt, M. Radparvar, S. Whiteley and S. Faris Summary: The eight mask-level circuit process described is based on reproducible, high quality, all-niobium Josephson junctions. The junctions are fabricated from in situ trilayer films of Nb/Al-AlO/sub x//Nb using the Selective Niobium Etching and Anodization Process (SNEAP). The quality of our junctions can be characterized by the figure of merit Vm, which is reproducibly greater than 40 mV at critical current densities of nearly 2 kA/cm/sup 2/. These junctions have been incorporated into an eight level process that has been used to fabricate a voltage standard, a time domain reflectometer (TDR), and other circuits. This paper will describe the eight level process, the junction characteristics, and the application of this process to circuit fabrication.         Fabrication and performance of all NbN Josephson junction circuits    M. Radparvar, M. Berry, R. Drake, S. Faris, S. Whiteley and L. Yu Summary: A novel process suitable for fabricating superconducting circuitry based on the all refractory material NbN is described. In this process, an in-situ trilayer film composed of NbN/MgO/NbN is used to fabricate Josephson tunnel junctions. Reactive ion etching processes are used to delineate devices and pattern insulators and metallizations. Fabricated junctions have yielded good tunneling characteristics with reasonable current density uniformity and reproducibility. Devices with gap voltages close to 5mV have been achieved for high quality junctions. In addition to the trilayer, there are two wiring layers, two resistor depositions, and two insulation layers, constituting a full NbN based fabrication technology. Using this process, we fabricated and successfully tested thin film DC SQUID and time domain reflectometer (TDR) circuits. Preliminary measurements suggest that the critical temperature of these circuits is well within the operating temperature of commercial two-stage closed cycle refrigerators.         Josephson integrated circuit process for scientific applications    R. Sandstrom, A. Kleinsasser, W. Gallagher and S. Raider Summary: We have developed and are regularly practicing a seven mask-level Josephson integrated circuit fabrication process tailored to dc SQUID requirements and intended for SQUID studies and other scientific applications of Josephson technology. The process incorporates low capacitance Nb/Nb/sub 2/O/sub 2//PbAuIn edge junctions, PdAu shunt resistors, and a wiring pitch of 5 /spl mu/m for the SQUID input coil level (which is PbAuIn). The junctions can be made as small as 2/spl mu/m by 0.3/spl mu/m, with a capacitance (including parasitics) of /spl sim/0.14 pF. This process yields stable and reliable junctions and integrated circuits.         High frequency properties of all-NbN nanobridges with gap structure in I-V curves    K. Hamasaki, T. Yakihara, Z. Wang, T. Yamashita and Y. Okabe Summary: All-NbN nanobridges with gap structure in I-V curves have been reproducibly constructed using RIE and lift-off techniques. The nanobridges had a width of 2 /spl mu/m, and a thickness of < 30 nm. The length or nanobridge was about of the order of 3 to 5 coherence length of epitaxial NbN films. The nanobridges had nearly ideal characteristics: sharply defined critical current, high resistance, well-defined gap structure at about 4 mV, large I/sub c/R/sub n/products of /spl sim/3 mV, and low excess current. Small-area dc SQUIDs were made using the nanobridges, and analyses of the response to magnetic flux were performed. The current-phase relationship of the nano-bridges was found to be close to sinusoidal. The maximum LC resonant voltage was about 1.2 mV, corresponding to a frequency of 580 GHz. The IF peak was obtained up to the bias voltage of about 4 mV in 101 GHz Josephson mixing.         Tunnel junctions with Nb/sub 3/Ge base electrode    M. Muck, H. Hedbabny and H. Rogalla Summary: For quasiparticle mixers for very high frequencies and ultrafast samplers, tunnel junctions with a large energy gap are needed. Large gap voltages should be possible with high-T/sub c/materials like Nb/sub 3/Sn or Nb/sub 3/Ge. We describe an in-situ preparation process for these junctions using Nb/sub 3/Ge as base electrode, and different superconductors as top electrode material. Because of poor results with native oxide layers, an artificial barrier was used. For this purpose, several oxides have been investigated. First results on these contacts, using several oxides and fluorides as barriers and Pb and NbN as top electrodes are presented.         A study of eddy-current effects in the structure of the westinghouse LCT coil    J. Luton, S. Shen, T. McManamy, C. Wilson, J. Ellis, L. Dresner and R. Wintenberg Summary: One of the six 2.5- X 3.5-m-bore 8-T superconducting magnets of the international Large Coil Task (LCT) was designed and fabricated by Westinghouse Electric Corporation with the oversight of Oak Ridge National Laboratory. This coil, designated WH, has a mechanical structure composed of a stack of aluminum plate segments held together with stainless throughbolts. When the magnetic flux through the coil is changed, voltage is induced in the structure, and to avoid excessive currents the design provided low-voltage insulation between plate segments. However, during construction it appeared that this anodizing layer may have been breached extensively. Electrical tests on delivery confirmed this, and supplemental instrumentation was added to the structure before the coil was installed in the test facility. The shorting raised concerns about increased refrigeration load, local overheating, and a change in dump characteristics. After installation, current ramps to 5 A showed magnetic diffusion time constants of 1.5 s at room temperature and 3.0 s at 20 K, an order of magnitude larger than for the other LCT coils. These latter coils have structural cases of stainless steel, which has an electrical resistivity 17 times that of the 2219-T87 aluminum used in the WH coil. In tests at operating currents, temporal values of voltage, current, temperature, and energy distribution during ramp and dump agree with those values calculated on the basis that the aluminum structure is solid, and are quite different from values calculated without considering shorting. On dump, the coil is partially self-protecting, but 23% of the initial stored energy is deposited in the structure at cryogenic temperature. The various effects of the shorting are apparently tolerable for testing in the International Fusion Superconducting Magnet Test Facility (IFSMTF). For other cases, the coil designer should carefully consider if and how the structure should be electrically segmented.         Advantages of the distributed structure concept of the Westinghouse LCP coil design-II    S. Singh, C. Heyne, D. Hackworth and P. Gaberson Summary: The forced flow Nb/sub 3/Sn magnet concept developed by Westinghouse in cooperation with the Oak Ridge National Laboratory offers the fusion program the option of a reactor size superconducting toroidal field coil which has the capability of achieving peak fields of 12 tesla. The Westinghouse LCP coil concept offers a number of advantages besides high field capability. The coil is fabricated by winding stainless-steel-jacketed conductors into machined slots in the structural plates. This configuration provides positive conductor support and prevents accumulation of magnetic loading on individual conductors. Another advantage of this concept is the distribution of the conductors which results in more uniform current density in the overall coil cross-section. This distributed winding approach also provides higher fields on the plasma axis for given peak fields on the conductor. The distributed structure uniformly distributes eddy current losses and has lower losses than lumped structure concepts when subjected to the pulsed poloidal fields. The higher current densities possible, due to more efficient utilization of space coupled with the use of materials with good radiation properties (materials used for the Westinghouse LCP coil), allows for reduction in reactor size, which can be a substantial cost advantage. The modular concept of the Westinghouse coil allows for parallel manufacturing operations. The maintainability and repairability aspects of the coil are also discussed.         Design and installation of instruments in the Westinghouse LCP coil    S. Singh and P. Gaberson Summary: The Westinghouse Electric Corporation completed the Nb/sub 3/Sn Superconducting toroidal field coil for the Large Coil Program (LCP) which is being managed by the Oak Ridge National Laboratory (ORNL). The coil design which features a force flow cooled conductor and a distributed aluminum plate structure has been described elsewhere [1,2,3,4]. A large number of instruments were installed in the coil because it is a first of its kind proof of concept device. This paper describes the installation of various sensors in the Westinghouse LCP coil.         Manufacture of the Westinghouse forced flow Nb/sub 3/Sn test coil for the large coil program    S. Singh, T. Hampton, T. Hordubay, P. Gaberson, R. Kibbe, W. Shipley and J. Young Summary: Manufacturing of the Westinghouse forced flow Nb/sub 3/Sn coil for the Oak Ridge National Laboratory Large Coil Program (LCP) is complete. The coil is installed in the Large Coil Test Facility (LCTF) at Oak Ridge National Laboratory and is being tested. The coil design concept is briefly presented to better understand the complexities of the manufacturing processes. This paper describes step-by-step procedures for the Westinghouse LCP coil manufacture. The facilities required and the training of the shop personnel are also discussed. The quality requirements and the quality procedures at each step of fabrication are described. Some of the serious problems which arose during manufacturing are pointed out along with the fixes to these problems. Some of the important development tasks needed for manufacture of this coil are listed. In every case, the completion of these tasks resulted in process modification prior to actual commitment to manufacture. This paper also highlights the major design and manufacturing advantages of the Westinghouse LCP coil. The goal of the Westinghouse LCP coil is to demonstrate the potential of Nb/sub 3/Sn for large scale applications to either high field or high current density magnets.         Experimental results of the 30-kA 70-cm-bore poloidal unit pancake    Y. Takahashi, H. Tsuji, K. Okuno, T. Ando, T. Hiyama, M. Nishi, E. Tada, K. Yoshida, K. Koizumi, H. Nakajima, T. Kato, M. Oshikiri, K. Kawano, Y. Ohgane, S. Kamiya, H. Mukai and S. Shimamoto Summary: A 30-kA, 70-cm-bore pulse coil was designed and fabricated. The charge-up test, the manual dump test and the heater test were carried out. The PUP was charged up to 30 kA at 5.8 T without any appearance of a normal zone. The manual dump from 30 kA at 9 T/s was carried out without any damage. In the heater test, the innermost one-turn normalcy at 30 kA and 5 T recovered spontaneously to the superconducting state in 10 s. These results indicate that the electromagnetic and the thermal performances are excellent.         Development of cryogenic electrical components for the demonstration poloidal coils    K. Yoshida, M. Nishi, E. Tada, K. Kawano, M. Oshikiri and S. Shimamoto Summary: Several cryogenic electrical components have been developed for the Demonstration Poloidal Coils (DPC) in Japan Atomic Energy Research Institute (JAERI). The test coils of the DPC were designed for high-voltage and forced-cooled conductors. The rated voltage of each coil is AC 6.9 kV. Maximum operating pressure is 20 atm. JAERI is developing and evaluating (1) insulation coupling, (2) instrumentation cable with new insulator, (3) a feedthrough for high voltage use, (4) a high-voltage isolation amplifier and (5) an amorphous silicon thermometer for use in high magnetic fields. The insulation coupling and feedthrough are designed on the specification of testing voltage AC 16 kV, testing pressure 30 atm and 1x10/sup -6/Acc/s helium leakage. The insulation coupling consists of glass-cloth-epoxy and stainless steel pipes. The feedthrough is made with ceramics. We usually use Teflon or polyimid (KAPTON) tape insulator for instrumentation cables at cryogenic temperatures. However, Teflon is not strong against irradiation and polyimid tape does not have a sufficient high voltage performance because of a withstanding corona. Therefore, poly-ether-imid (PEI) is selected because of its irradiation and corona withstanding. Amorphous silicon thin film has a good sensitivity in the range of 4 K - 30 K and exhibits few magnetic field influences. The stability of amorphous silicon may be high because amorphous silicon has good mechanical and chemical properties. This element can be applied to thermometers in a high magnetic field environment.         Structural behavior of winding and superconductor under mechanical loading    H. Nakajima, K. Yoshida, Y. Hattori, K. Koizumi, M. Oshikiri and S. Shimamoto Summary: This paper describes the structural behavior of pool-cooled windings for a pulsed coil under both mechanical and magnetic forces. Mechanical expansion and compressive loading were applied to a pool-cooled single pancake winding in order to evaluate equivalent Young's moduli of winding in the radial and axial directions, respectively. On the other hand, magnetic force was applied to a similar double pancake in the experiment of the Poloidal Unit Pancake (PUP). It was demonstrated that a winding rigidity test under mechanical loading was available to predict the structural behavior of superconducting coils.         Simulation of electric arc with hysteresis during discharge of a fusion superconducting magnet system    H. Kraus and J. Jones Summary: Simulation of an internal voltage induced arc strike and attendant voltage-current hysteresis characteristics in an FED/INTOR scale superconducting magnet and circuit protection system during discharge was performed. To begin, an analytical solution was used to investigate system response for an internally shorted magnet and simplified circuit protection system during magnet discharge. The short produced a current split within the magnet resulting in a transformer like mutual inductance effect. Thus, the coupling coefficient was introduced in the equations to be physically realistic and to prevent degeneration of the associated eigenvalue problem. The effects of varying short resistance, dump resistance, and number of coil turns shorted are presented. This led to simulation of an arc strike, including hysteresis effects, which is then compared to the usual constant resistance used to simulate magnet shorts. Tracking of arc characteristics was made possible through specially developed multiple tripping capabilities recently incorporated into MSCAP (Magnet Systems Circuitry Analysis Program) for safety and instrumentation control simulation.         A 12-T forced flow type superconducting magnet    M. Nishi, Y. Takahashi, T. Ando, S. Shimamoto, H. Takei and K. Ohkura Summary: As part of the development work for the high field superconducting toroidal field coil for a tokamak fusion reactor, a 12-T 4-kA forced-flow type superconducting coil was designed, fabricated, and tested. The objective of this coil is to verify that a coil wound by the Nb/sub 3/Sn cable-in-conduit type conductor can generate a magnetic field of 12 T. The test was carried out with a background field of around 8 T, and a total magnetic field of 12.0 T was achieved with the transport current of 4.0 kA. The average current density in the winding area was 60.5 A/mm/sup 2/at that time. These results demonstrate that high-field, large-current and high-current-density coils can be fabricated with a cable-in-conduit type conductor.         Stainless steel sheathed forced internally cooled Nb/sub 3/Sn superconductor and its coil test    K. Agatsuma, K. Kaiho, K. Komuro, M. Sugimoto, Y. Ikeno, M. Nakagawa and O. Kohno Summary: Forced cooled Nb/sub 3/Sn superconducting coil with the stainless steel sheathed conductor has been manufactured and tested in a High Field Test Facility (HFTF). Some properties of the sheath material and the conductor with stainless steel sheath have been investigated. A 316L stainless steel sheathed conductor (the outer dimension of 13 X 23 mm/sup 2/) was fabricated, and one coil was completed by the wind and react method using this conductor. The coil was connected with 8 pancake coils made of copper sheathed conductor. The forced cooled magnet of 9 double pancake coils was tested under 5.9 T of the back up field in HFTF and generated 8.8 T under 7.6 kA of transport current. Experimental results show that the Nb/sub 3/Sn strand in the copper sheathed conductor near the connector was degraded due to handling through reconnecting the conductor for several times.         Flow effect of supercritical helium on the stability of a hollow superconducting coil (SHETEM2a) with thermal load    N. Ohuchi, J. Yamamoto and Y. Murakami Summary: The influence of mass flow rate and thermodynamic state, and heating intensity on the stability of a hollow superconducting coil cooled by supercritical helium (SHE) was analyzed when the entire conductor was uniformly heated. The hollow conductor was 87 m long and had a 3.0-mm-ID cooling channel. It was found that the coil was fully safe when the thermal load which was given to the conductor for the transit time of SHE in the coil was smaller than the energy needed to increase the SHE temperature to the critical temperature of the coil.         Transient stability analysis of a forced cooled superconductor    K. Agatsuma Summary: A numerical analysis of stability and thermal performance of internally cooled superconductors has been investigated. An analysis of this system has been performed using one dimensional computer code developed by Arp based on a program for nonliner partially differential equations by Sinovec and slightly modified by the author. The effects of helium mass flow rate and also hydraulic perimeter upon the stability margin has been studied. The computer simulation results will be presented. These results of computer analyses indicate that the thermally induced pressure gradients and fluid velocity caused by rapid perturbations are responsible for the stability margin, and both of mass flow rate and hydraulic perimeter are quite significant for high stability margins. A composite cooling channeled forced cooled superconductor will be suggested from these results.         The initial filament strain state of cable-in-conduit superconductors and the relation of this strain to large-bore, high-field magnet design    J. Miller, M. Chaplin, L. Summers, M. Steeves and M. Hoenig Summary: Cable-in-conduit superconductors formed by enclosing a cable of MF-Nb/sub 3/Sn/Cu composites in a strong steel sheath are a useful element in magnet design and construction. However, an important feature of this type conductor, which must be understood and accounted for in magnet design, is the initial strain state of the superconducting filaments. This initial strain state results from the differential cooldown strains of the various components of the cable-in-conduit system as this system is brought from the Nb/sub 3/Sn formation temperature (/spl sim/1000 K) to the operation temperature (/spl sim/4 K). The resultant strain depends on the proportions and thermomechanical properties of the constituent materials. However, empirical data suggest that the initial strain state also depends on the void fraction in the cable. In this paper, we survey the literature to provide data for a simple model to describe the mechanical link between cable and sheath. We also report on new experiments devised to further clarify this link. In addition, we discuss using the initial superconductor strain state as a parameter in magnet design.         The development of superconductors for applications in high-field, high-current-density magnets for fusion research    L. Summers and J. Miller Summary: The development of large-bore, high-field magnets for fusion energy applications requires a system approach to both magnet and conductor design. At Lawrence Livermore National Laboratory (LLNL), the criteria used to choose superconductors include: strain tolerance, radiation tolerance, heat removal, stability, fabricability, and cost. We report on the performance of industrially produced, prototype, Ti-modified Nb/sub 3/Sn wires developed with LLNL support. Wire performance characteristics evaluated include critical current as a function of magnetic field, temperature, and applied strain. Tests were performed to determine how this performance translates to the performance of a cable-in-conduit conductor system using this wire. An alternative to Nb/sub 3/Sn superconductors is NbN, which is strain and radiation insensitive. We report preliminary efforts to produce multifilamentary NbN conductors by liquid-metal infiltration of NbN-coated, high-strength fibers. In addition, we discuss the fabrication of multifilamentary NbN conductors and their possible impact on magnet design.         Longitudinal propagation velocity of the normal zone in superconducting wires    H. ten Kate, H. Boschman and L. van de Klundert Summary: The longitudinal propagation of the normal zone in superconducting wires was experimentally investigated in order to evaluate existing analytical expressions which attempt to describe the propagation velocity in a more or less simple manner. The availability of a reliable expression is important for application in computer codes that calculate quench evolutions in superconducting magnets. We measured the propagation velocity as function of transport current and magnetic field in five different insulated NbTi superconductors having a copper, a copper-nickel or a mixed matrix. The comparison to calculated velocities using five existing models showed that large quantitative and qualitative differences exist.         Normal-zone propagations inside a layer and between layers in a superconducting coil    K. Funaki, K. Ikeda, M. Takeo, K. Yamafuji, J. Chikaba and F. Irie Summary: We have investigated the propagation of normal zones in an alternate layer structure of conductor and non-conductor parts. In order to evaluate average propagation velocity in the alternate layer structure, a heat balance equation was set up for a coarse-grained spatial unit composed of a pair of conductor and non-conductor layers. An analytical expression of the propagation velocity was obtained for the coarse-grained layer structure with uniform thermal properties. We measured the propagation velocity from turn to turn in a single-layer superconducting solenoid coil with a teflon spacer between turns. The velocity decreased in proportion to the 0.5-1 power of the thickness of the spacer. The experimental results were quantitatively explained by the present theory. We also discussed an anisotropy of the normal-zone propagation in both impregnated and unimpregnated superconducting coils on the basis of the present theoretical results.         Transient heat transport in superfluid helium in cylindrical geometry    J. Rogers and D. Brown Summary: Heat transport in cylindrical space from a round superconductor immersed in a finite bath of superfluid has bean analyzed both numerically and analytically. The computer and closed analytical results are essentially the same. Analytical equations are given for the temperature of the helium bath as a function of radius, time, and heat flux from the conductor and for the time to reach the superfluid to normal helium transition temperature at the conductor as a function of heat flux.         On mathematical modelling of transition processes of the composite superconductors into the normal state    V. Romanovskii Summary: The generalized mathematical models for thermal processes in current carrying elements of superconducting magnetic systems have been compared. The features of the dimensionless analysis of their operating conditions have been shown. They depend on choice of the characteristic linear dimension which is used for the dimensionless action of the initial dimensional model.         Quench detection of superconducting magnet by dual-core optical fiber    O. Tsukamoto, K. Kawai and Y. Kokubun Summary: We demonstrated that a temperature rise of 1.0 K was detectable at 4.2 K using a dual-core optical fiber. The fiber has two single-mode optical cores in one fiber. Using this technique, we detected a quench of a superconducting magnet by detecting temperature rise due to joule heating caused by normal transition. A quench detector using this optical method is immune from electromagnetic noise, free from troubles caused by break-down of electrical insulator, and has many advantages over a conventional quench detector measuring voltages of a magnet.         Cryostatic stability of miniaturized composite conductors    W. Feng and T. Frederking Summary: We have investigated the enhancement of the stability limits for miniaturized fine filament composites (NbTi-Cu) with type II diameters in the 1 /spl mu/m range and below. The overall current densities have been evaluated. They are affected by permeabilities of coolant flow through narrow passages of cable-in-conduit type configurations which tend to be laminarized by miniaturization.         AC losses in superconducting cables designed for generator field windings    H. Neumuller and L. Intichar Summary: In order to evaluate a conductor design suitable for a superconducting generator field winding, the loss behavior of different types of superconductors has been investigated. The cabled conductors tested have identical dimensions and nominal currents of 6000 A at 7 T but different matrix configurations, comprising pure Cu or Cu/CuNi matrices. Two different field variation modes were applied to the specimens: triangular and sinusoidal sweeps up to 6 Hz. From the experimental results the different loss components were separated according to theory. The maximum interstrand coupling loss amounts to a factor of less than two compared with filament coupling in the case of Cu matrix conductors. Since in a generator rotor the winding is additionally compressed by centrifugal forces, investigation of the loss behavior of sample coils under mechanical pressure was started in a modified apparatus.         Numerical solutions of the current distribution in superconducting cables    R. Hartmann, P. Rem and L. van de Klundert Summary: Superconducting cables are described by current sheets using the continuum model of W. Carr Jr. [1] and assuming an anisotropic conductivity. Two different situations are considered: a) finite length of cable in spatially independent magnetic field; b) infinitely long cable in a periodical magnetic field.         Effect of composite structure on AC loss of superconducting wire    Y. Tanaka, K. Matsumoto, M. Yamamoto, O. Tsukamoto and T. Ishigohka Summary: Investigations of quenching currents, stability and ac losses for two kinds of NbTi multifilamentary cable with very fine filaments are presented. Both of them comprise six strands of 0.1 mm diameter with many filaments of 0.5 /spl mu/m dia. and a stainless steel strand of 0.1 mm diameter for reinforcement. These cables are epoxy-impregnated for practical windings. Even these designs result in good stability and low ac losses. If these cables are used in ac magnets, generating a maximum field of ac around 1.0 T, economical benefits are expected at power frequencies, 50 Hz/60 Hz.         Characteristics of epoxy-impregnated AC superconducting winding    O. Tsukamoto, T. Ishigohka, M. Yamamoto, Y. Tanaka and H. Kobayashi Summary: AC superconducting composite wires for 50-60 Hz application are very susceptible to disturbances due to wire motions, because main matrices of the wires are highly resistive CuNi. Instability of the wires is one of the most serious problems to develop AC wires of large current capacity. An effective technique to reduce the wire motions is to impregnate the windings. We investigated characteristics of the epoxy-impregnated AC superconducting windings. It was demonstrated that the stability was much improved by the impregnation, and that the AC losses could be cooled by the heat conduction through the epoxy without significant wire-temperature rise, provided that the thickness of the epoxy-impregnated layer was less than about 2 mm.         Relation between radial stress and quench current for tightly wound dry solenoids    M. Urata and H. Maeda Summary: Premature quenches in superconducting solenoids, wound by Formvar coated NbTi conductors, has been studied. Radial compression between winding layers is supposed to be essential to suppress conductor motions; the relation between radial stress distribution in the winding and quench current is investigated by experiment for a model magnet. The result is discussed based on the stress calculation and frictional characteristics of the Formvar coated conductor.         Instabilities due to mechanical strain energy in superconducting magnets    J. Chikaba, F. Irie, K. Funaki, M. Takeo and K. Yamafuji Summary: In order to investigate fundamental mechanisms of winding motions during charging superconducting magnets, single layer, 2- layer and multilayer (10 turns, 29 turns) test magnets were used. The winding motion was detected as mechanical strains and acoustic emission (AE). Compressive strains which appeared in the axial direction of the magnet showed large hysteresis when it was charging and discharging. It was clarified that the hysteresis directly resulted in frictional losses and the AE signal. Microslips (0.36 /spl mu/m /spl sim/ 0.5 /spl mu/m) and dissipation energies were estimated by the hysteresis curves and were compared with the AE energy. It was also suggested that the magnet instability tends to increase in the vicinity of its ends, because the microslips are accumulated toward the center of the magnet.         Propagation of a normal zone along superconducting wires suspended in a liquid helium bath    J. Casas and L. Rinderer Summary: Experimental and theoretical normal zone velocities have been obtained for superconducting tin wires in a normal and superfluid helium bath. Published theoretical calculations assume a flat normal-superconductor (N-S) boundary. A shape of the N-S boundary that results from a radial destruction of superconductivity in the moving front is calculated. For the sample in superfluid helium, the calculations are in good agreement with the experimental data. In normal helium no agreement between experimental and theoretical data can be obtained without introducing a transient heat transfer coefficient between the wire and the bath.         Advances in production of high purity Nb for RF superconductivity    H. Padamsee, D. Smathers, R. Marsh and B. VanDoran Summary: In the last three years, the purity of commercially available Nb has improved a factor of 10 in response to the needs of rf superconductivity for application to electron-positron storage rings for high energy physics as well as to electron linacs for nuclear physics and free electron lasers. Yttrification of this premium quality Nb enhances the purity by yet another factor of 2-3. Superconducting cavities built with high purity Nb provide higher accelerating gradients, increasing roughly as the square root of the purity enhancement. Results are presented on analysis of the interstitial impurity content on the ingot and final sheet product as well as on the sheet properties of the final product that are important to cavity manufacturers, such as residual resistivity ratio, yield strength, grain size, etc. Prospects for further advances are discussed.         Influence of oxide layers on the microwave surface resistance of niobium    F. Palmer Summary: We have investigated the effects of oxide layers on the microwave surface resistance of 8.6 Ghz superconducting niobium cavities. Cavities were UHV fired to remove oxides and then tested before and after exposure to oxygen. Microwave measurements were made on oxide layers grown and maintained room temperature and on layers which had been heated to 300C. The contribution to residual resistance from oxide layers kept at or below room temperature is less than 2 or 3 n-ohm. Heated layers showed a 20% decrease in B.C.S. resistance, and a 40 n-ohm increase in residual resistance. Heating unoxidized cavities to 300C has no effect, demonstrating that these cavities were actually oxide free.         Comparative measurements of niobium sheet and sputter coated cavities    G. Arnolds-Meyer and W. Weingarten Summary: Comparative measurements of sheet metal and sputter coated Nb cavities were performed at 500 MHz. The sputter coated ones had a higher low field Q, a stronger decrease of Q with the accelerating field, and showed no static magnetic field dependence of the Q value. Throughout the layer, larger amounts of impurities were found, which may explain the experimental results.         Performance of a superconducting cavity stabilized ruby maser oscillator    D. Strayer, G. Dick and J. Mercereau Summary: We first described an all-cryogenic oscillator system at the 1982 Applied Superconductivity Conference in Knoxville. This oscillator consists of a ruby cavity maser stabilized by a high-Q superconductor-on-sapphire resonator. The maser provides gain with very low noise and small power dissipation, while the sapphire substrate's thermal coefficient of expansion is 100 times smaller than that of superconducting metals. Having tested the major components and proved them satisfactory to the design, we have now assembled the first such oscillator and tested its performance in several preliminary configurations. The results of stability tests in a more advanced configuration will be reported. We shall describe this oscillator and shall report on its performance as a high-stability frequency source.         Structure and superconducting property characterisation of MF Cu/Nb - 46.5 w% Ti superconductors    J. Somerkoski, D. Hampshire, H. Jones, R. Toivanen and V. Lindroos Summary: Optical microscope-, SEM-, TEM- and AES-facilities were used to comprehensively characterise metallurgical structures of composites comprising of 60 Nb-47.1 w% Ti filaments embedded in copper matrix and having various thermomechanical treatment histories. Superconducting properties were measured at temperatures of 4.24 K and 2.50 K at magnetic fields up to B/sub c2/. At 4.2 K, an optimum microstructure produces technically interesting high critical current carrying capacities at low, mid and high magnetic field regimes, and at 2.5 K the critical current densities suggest utility of nominal 46.5 w% Ti alloys at magnetic fields up to 11 T. The improvements in superconducting properties are associated with refinement of well defined sub-band boundaries to an optimum spacing of 20 nm, whereas extensive final cold working results in distorted microstructure having additional dislocation related diffuse boundaries and, consequently, an impaired superconducting performance at low and mid magnetic field regimes.         Relationships between critical current and stress IN NbTi    J. Ekin Summary: The effects of various types of stress on the critical current of a multifilamentary NbTi superconductor are reported. Degradation of critical current due to axial tension applied at 4 K, transverse compression applied at 4 K, and hairpin bending strain applied at room temperature has been measured. The degradation from axial tension is much greater than from transverse compression in many practical cases because the soft copper matrix limits the build-up of transverse compression. The degradation from typical levels of transverse compression is only about 4% at 8 T, for example. For axial tension, on the other hand, higher stresses can occur that will degrade the critical current by 24%, for example, at 7 T and 2.7% strain. Both the axial-tensile and the transverse-compressive stress effects are about 98% reversible; thus the degradation will be seen only when the conductor is under operational stress. The results indicate that a primary origin of the critical current degradation in NbTi is a stress-induced reversible decrease in the upper critical field.         Precipitation at low strains in Nb 46.5 wt% Ti    M. Buckett and D. Larbalestier Summary: The effects of a given heat treatment at 300 to 500 C in the 2 phase region in cold worked Nb 46.5 wt%Ti have been studied. Empirically it has been observed that the effect of such heat treatments on the critical current density are not predictable unless the treatments are delayed until a prior strain of 5 to 7 has been given. In this study, heat treatments at strains of 2 and 5 are discussed. It is shown that precipitation is strongly dependent on the heterogeneous nucleation site density. Precipitation is thus much more non-uniform at /spl epsiv/=2 than at /spl epsiv/=5. The /spl omega/ phase is seen after heat treatment at 375 C at a strain of 2 but only /spl alpha/ was seen on increasing the temperature or strain. Grain boundary film precipitation was only seen at a strain of 5.         Studies of NbTi strands extracted from coreless Rutherford cables    L. Goodrich, E. Pittman, J. Ekin and R. Scanlan Summary: The electromechanical properties of NbTi strands extracted from coreless Rutherford cables were studied to clarify the relative effects of strand location and field angle on current degradation that occurs in cables that have been compacted into a keystone shape. Detailed critical-current measurements were made on two samples which were fabricated under controlled conditions. These are prototype cables for high energy physics applications. Specific factors that are addressed are the nature, location, and amount of degradation. This information is intended to lead to methods for reducing the amount of critical-current degradation in cable manufacture.         Very high current density niobium Titanium composites    Li Chengren and D. Larbalestier Summary: The effects of increasing the heat treatment temperature in Nb 46.5 wt% Ti have been studied. The study has been confined to processes involving two or three heat treatments, since these are most compatible with an industrial scale process. Very high J/sub c/values have been obtained using process variables significantly different from those normally used. In particular, we find that increasing the heat treatment temperature and the final drawing strain are very helpful in raising J/sub c/. The maximum J/sub c/values (at a sensitivity of 10/sup -14//spl Omega/m) of 3680 A/mm/sup 2/(5 T, 4.2 K) and 1560 A/mm/sup 2/(8 T, 4.2 K) were obtained for heat treatments at 420/spl deg/C and for final drawing strains exceeding 5.         Integrated thin-film dc SQUID sensors    M. Ketchen Summary: This paper reviews the design of integrated thin-film dc SQUID sensors fabricated in planar technology. Included are both high performance devices with fully integrated input coils and more advanced devices that incorporate fully integrated pickup loop structures as well, such as gradiometers and miniature susceptometers and magnetometers. First the basic characterization of the dc SQUID is given. Operation and performance issues are discussed followed by a review of the status of planar coupling schemes. A brief discussion of packaging is given. Design considerations for planar gradiometers are presented. The configuration of a balanced coupled SQUID for gradiometer applications is detailed, and some key design concerns for gradiometer arrays are mentioned. The design and application of a miniature SQUID susceptometer is reviewed, and a brief description of several other miniature susceptometer and magnetometer designs is given.         Electron trap states and low frequency noise in tunnel junctions    C. Rogers, R. Buhrman, W. Gallagher, S. Raider, A. Kleinsasser and R. Sandstrom Summary: We present the results of measurements of the low frequency excess, or 1/f, noise in small area Nb/Nb/sub 2/O/sub 2//PbBi and Nb/Nb/sub 2/O/sub 2//PbAuIn tunnel junctions. Our study shows that the low frequency noise in all of these devices arises from fluctuations in the tunnel barrier transmission coefficient due to changes in the barrier shape. These time dependent barrier deformations appear to be due to charge capture and emission by electron traps in the tunnel barrier material. We find that Nb/sub 2/O/sub 2/barriers prepared either by Reactive Ion Beam Oxidation (RIBO) or by the Raider-Drake Plasma Oxidation process have one particular type of charge trap which dominates the noise spectrum. The density of these noise sources can be controlled in a variety of ways: Improved processing techniques result in higher quality Current-Voltage characteristics and a simultaneous decrease in the density of noise sources. Further, we find that ion implantation of the barrier with Boron results in a decrease in the density of noise sources. The detailed energy density of states for the noise sources also can be modified by thermal cycling and by application of large bias voltages. We will discuss the implications that our single tunnel junction measurements have for the production of extremely low noise SQUID magnetometers.         Excess noise in dc SQUIDs from 4.2K to 0.022K    F. Wellstood, C. Urbina and J. Clarke Summary: Four types of excess noise have been identified in dc SQUIDs operated in the temperature range 0.022 to 4.2 K. At temperatures between about 2 and 4 K, the spectral density of the low frequency flux noise of a wide variety of thin-film dc SQUIDs scales as 1/f/sup m/where m = 1.0 /spl plusmn/ 0.1. In SQUIDs with Nb loops the noise originates as an "apparent flux noise", whereas in those with Pb or PbIn loops the noise is substantially lower and originates in critical current fluctuations. When any of these devices is cooled to temperatures below about 0.5 K, the spectral density of the excess flux noise scales as 1/f/sup m/, with m = 0.66 /spl plusmn/ 0.08 in most cases, and the noise always originates as an apparent flux noise. At the lowest temperatures, the white noise saturates at an effective temperature of about 150 mK; this excess noise probably arises from self-heating in the resistance shunting each tunnel junction.         Subpicosecond optoelectronic study of superconducting transmission lines    C. Chi, W. Gallagher, I. Duling, D. Grischkowsky, N. Halas, M. Ketchen and A. Kleinsasser Summary: We have studied the propagation of subpicosecond electrical pulses on coplanar superconducting Nb transmission lines. Pulses with 0.6 ps full width at half maximum were generated by photoconductively shorting a /spl sim/10 /spl mu/m region between two charged 1 to 5 /spl mu/m lines separated by a 2 to 10 /spl mu/m gap. The propagating pulses were sampled by the delayed shorting of a fast phototconductive switch between a sampling probe and one of the transmission lines at variable distances away from the generation point. Silicon-on-sapphire wafers served as the transmission line substrate, with the 0.5 /spl mu/m thick Si layer heavily damaged by an oxygen implant to provide the subpicosecond carrier life time for the excitation and probe switches. Measurements and analyses of pulses propagated up to 8 mm distance at temperatures from 2 K to 10 K showed a threshold for strong attenuation and dispersion at a frequency reflecting the onset of pair breaking in the superconducting transmission lines. The results at least qualitatively confirm the superconducting microstrip transmission line calculations of Kautz based on Mattis and Bardeen's formulae for the complex conductivity of superconductors.         Current-voltage characteristics of nanoampere Josephson junctions    R. Ono, M. Cromar, R. Kautz, R. Soulen Jr., J. Colwell and W. Fogle Summary: We have studied the current-voltage characteristics of small area tunnel junctions at temperatures below 1 K. The junctions were made in an edge geometry with a Nb base electrode and had areas less than .05 /spl mu/m/sup 2/and critical currents in the nA range. Although the measured I-V characteristics resemble those of ordinary hysteretic junctions, the supposed zero-voltage portion of the curve proved to have a finite slope and to deviate from zero voltage. For these junctions it is apparently possible for occasional 2/spl pi/ phase slips to occur without switching to the usual voltage state. This behavior can be explained either by macroscopic quantum tunneling or by a model in which the effective shunt conductance of the junction is frequency dependent.         A novel hot-electron transistor employing superconductor base    M. Tonouchi, H. Sakai, T. Kobayashi and K. Fujisawa Summary: A design and preliminary experiments on a new monolithic hot-electron transistor employing superconductor-base (Super-HET) were demonstrated. A prepared device comprising n+-GaAs / Nb (200 /spl Aring/) / /spl alpha/-InSb / Au multiple-layer exhibited the common-base current amplification factor as high as 0.8 at the liquid helium temperature. The theoretical calculation and Monte Carlo simulation predicted a higher transfer efficiency (96%) as well as the ultra-fast (femto-second order) data rate processing of our Super-HETs. The NbN epitaxial growth on semiconductor was studied and successfully achieved by introducing 5/spl Aring/ MgO buffer layer at the interface.         First results of the full-array LCT coil tests    S. Shen, L. Baylor, J. Clinard, F. Cogswell, L. Dresner, J. Ellis, W. Fietz, W. Fletcher, P. Haubenreich, W. Herz, Y. Iwasa, B. Jakob, S. Kamiya, T. Kato, M. Lubell, J. Lue, J. Luton, T. McManamy, H. Mukai, K. Okuno, S. Schwenterly, L. Siewerdt, R. Stamps, A. Ulbricht, C. Wilson, R. Wintenberg, R. Wood, F. Wuechner and J. Zichy Summary: The international Large Coil Task (LCT) has designed, built, and is testing six different toroidal field coils. Each has a 2.5- X 3.5-m D-shaped bore, a current between 10 and 18 kA, and is designed for stable operation at 8 T. Three coils are bath-cooled; three are cooled by forced flow of helium at supercritical pressure. One uses Nb/sub 3/Sn; the others NbTi. The test coils are equipped with voltage, temperature, magnetic field, flow pressure, strain, displacement, and acoustic emission sensors sufficient for penetrating analysis of performance field. Shakedown operation of the test facility and preliminary tests of the first three coils were accomplished in 1984. Tests of the full six-coil toroidal array began early in 1986 and have progressed to the stage of design-current, design-field stability tests. Results to date have elucidated complex structural and electrical interactions in a multicoil array and provide gratifying assurance of coil performance.         Testing of the pool-boiling cooled Japanese LCT coil in the international fusion superconducting magnet test facility    K. Okuno, T. Kato, K. Koizumi, H. Tsuji, T. Hiyama, S. Shimamoto, Y. Hattori, S. Kamiya, H. Mukai and F. Iida Summary: The Japanese LCT coil has successfully achieved the design field of 8 T in the toroidal array of the six LCT coils. In March, 1986, tests of the LCT coils were started following the cooldown of the whole facility. In the single-coil test and design-point test, in which the maximum field was 6.4 T and 8.1 T, respectively, the coil was charged, discharged, and dumped under different conditions. A recovery test and a simulated nuclear heating test were performed to investigate the stability of the coil. Measurements of displacement under the several conditions of electromagnetic load were analyzed to explain the mechanical behavior of the coil. Results obtained in the tests are reported in this paper.         Preliminary results of the U.S. pool-boiling coils from the IFSMTF full-array tests    J. Lue, L. Dresner, M. Lubell, J. Luton, T. McManamy and S. Shen Summary: The Large Coil Task to develop superconducting magnets for fusion reactors, is now in the midst of full-array tests in the International Fusion Superconducting Magnet Test Facility at Oak Ridge National Laboratory. Included in the test array are two pool-boiling coils designed and fabricated by U.S. manufacturers, General Dynamics/Convair Division and General Electric/Union Carbide Corporation. So far, both coils have been energized to full design currents in the single-coil tests, and the General Dynamics coil has reached the design point in the first Standard-I full-array test. Both coils performed well in the charging experiments. Extensive heating tests and the heavy instrumentation of these coils have, however, revealed some generic limitations of large pool-boiling superconducting coils. Details of these results and their analyses are reported.         Testing of the Euratom LCT-coil, a forced-flow cooled NbTi coil, in the international fusion superconducting magnet test facility (IFSMTF)    W. Herz, H. Katheder, P. Komarek, W. Maurer, G. Nother, S. Shen, L. Siewerdt, M. Susser, A. Ulbricht, F. Wuchner and G. Zahn Summary: The Euratom-LCT-coil was tested as a single coil in the TOSKA facility at KfK Karlsruhe and in IFSMTF at ORNL Oak Ridge. Different mechanical boundary conditions and other operation parameters (mass flow, current) in the IFSMTF led to new set of results which broaden the knowledge about the coil. During cooldown the coil showed excellent heat transfer properties. The design current 11.4 kA with a max. field of 6.63 T could be reached with a ramp rate of 4 A/S without visible instabilities and thermal losses. The coil had at rated current a Stekly parameter /spl alpha/ = 2.3 and could safely operated outside the cryogenic stability regime. The coil was 7 times dumped from currents higher than 4 kA with a peak voltage of 2.5 kV. Pressure increase was investigated under different boundary conditions and remained moderate. Dump losses measured were about 2 % of the stored energy. The coil was two times quenched during investigation of the operation limits. The quench detection system specially developed for this coil could be successfully tested with a level setting of 50 mV. For the first time the operation limits of such a coil were determined by current sharing measurement with heated helium slugs. The results are in fair agreement with those extrapolated from single strand measurements.         Preliminary test results of the Swiss LCT-coil    G. Vecsey, I. Horvath, B. Jakob, P. Weymuth and J. Zichy Summary: The Swiss (CH) LCT-coil is the contribution of Switzerland to the international Large Coil Task (LCT) at Oak Ridge National Laboratory (ORNL) in Tennessee, USA. After delivery in February 1984, the CH coil was tested only cryogenically during the Partial-Array Test in the summer of the same year. The first opportunity to energize the CH coil arose during the on-going Six-Coil Test. The cooldown started on January 18, and all coils became superconducting on February 18, 1986. Checking the sensors of the CH coil and remeasuring of its cryogenic parameters began on March 25. Subsequently, the coil was energized up to its full nominal current of 13 kA, creating thereby a self-field of 6.4 T on the conductor. This test period ended on April 16 with experiments simulating the nuclear heating present in a fusion reactor as additional load on the winding. This paper presents the data taken during the cooldown and the successful single-coil test. The cooldown data and the cryogenic parameters of the coil are compared to the results of the Partial-Array Test. The interpretation of the data taken while the coil was energized as a single coil is preliminary and will be further investigated.         First tests of the westinghouse coil in the international fusion superconducting magnet test facility (IFSMTF)    L. Dresner, D. Fehling, M. Lubell, J. Lue, J. Luton, T. McManamy and S. Shen Summary: The Westinghouse coil is one of the three forced-flow coils in the six-coil toroidal array at the IFSMTF at Oak Ridge National Laboratory. It is wound with a 17-KA, Nb/sub 3/Sn/Cu, cable-in-conduit superconductor supported structurally by aluminum plates and cooled by 4-K, 15-atm supercritical helium. The coil is instrumented to permit measurement of helium temperature, pressure, and flow rate; structure temperature, strain, and displacement; field; and normal zone voltage. A resistive heater has been installed to simulate nuclear heating, and inductive heaters have been installed to facilitate stability testing. The coil became superconducting on February 13, 1986, and has been tested as a single coil. The tests covered charging to design current and current-sharing tests using the resistive heater. Future tests will include operation in the full six-coil array, stability tests using pulsed inductive heaters, exposure to a pulsed magnetic field, extended operation above 100% of design current, and extended operation at design current at temperatures above 4.2 K.         Construction and operation of the 12-T superconducting coils for the mirror fusion test facility    J. Zbasnik, T. Kozman, D. Shimer and D. Hathaway Summary: We have successfully constructed and tested a pair of high-field coils that is part of the magnet set of the Mirror Fusion Test Facility (MFTF-B) at the Lawrence Livermore National Laboratory. Each coil consists of a multifilamentary Nb/sub 3/Sn magnet nested inside a multifilamentary NbTi magnet. During our test, these coils produced a central field of 12 T, with a peak conductor field of 12.5 T. The dimensions of the Nb/sub 3/Sn insert coil are: 0.36-m bore, 1.32-m outer diameter, and 1.14-m overall length. These coils were designed to be fully cryogenically stabilized and cooled by pool-boiling liquid helium. The operating current density of the Nb/sub 3/Sn coils is 2000 A/cm/sup 2/and 2400 A/cm/sup 2/for the NbTi magnet. In this paper, we present design considerations and details, construction techniques, and operational results of these coils.         Liquid helium cooling of the MFTF superconducting magnets    J. VanSant and J. Zbasnik Summary: During acceptance testing of the Mirror Fusion Test Facility (MFTF), we measured these tests: liquid helium heat loads and flow rates in selected magnets. We used the data from these tests to estimate helium vapor quality in the magnets so that we could determine if adequate conductor cooling conditions had occurred. We compared the measured quality and flow with estimates from a theoretical model developed for the MFTF magnets. The comparison is reasonably good, considering influences that can greatly affect these values. This paper describes the methods employed in making the measurements and developing the theoretical estimates. It also describes the helium system that maintained the magnets at required operating conditions.         System design of the demonstration poloidal coils and the test facility    E. Tada, S. Shimamoto, T. Ando, T. Hiyama, H. Tsuji, Y. Takahashi, M. Nishi, K. Yoshida, K. Okuno, K. Koizumi, T. Kato, H. Nakajima, K. Kawano, M. Oshikiri, M. Hoshino, Y. Ohgane, E. Yaguchi and P. Phelan Summary: A program of large pulse coils for investigation of superconducting pulse-coil technology required for the Fusion Experimental Reactor (FER) has been conducted. In this program, the pulse coils are separated into three coils (DPC-U1, U2 and EX) with forced-flow superconductor cooled by supercritical helium at 350 g/s under conditions of 10 bar and below 4 K. For this purpose, a new cryogenic pump system, which is composed of a circulation pump and a cold compressor, is developed and installed in the existing Superconducting Engineering Test Facility in order to produce and circulate supercritical helium at 500 g/s in the maximum. A newly developed vapor-cooled current lead with a cable-in conduit shape has been selected for the current leads and its rated current and insulation testing voltage are specified to be 30 kA and AC 16 kV, respectively. In addition, for pulse operation of the coil system, the JT-60 power supply system, which has a maximum capacity of /spl plusmn/ 92 kA and /spl plusmn/ 2.5 kV, is connected to charge the coils. The latest design and development status of this facility are described in this paper.         Evaluation of various fabrication techniques for fabrication of fine filament NbTi superconductors    R. Scanlan, J. Royet and R. Hannaford Summary: The successful fabrication of a fine filament high current density NbTi superconductor can have a significant impact on the cost of the Superconducting Supercollider. Consequently, we have been exploring various approaches for fabricating this type of superconductor, in collaboration with several superconductor wire manufacturers. The techniques investigated include double conventional hot extrusion, large single stack conventional hot extrusion, and warm hydrostatic extrusion. The important conductor properties (critical current density, piece length, yield, and cost) will be compared for the various approaches. Finally, the feasibility of manufacturing production quantities of a fine filament conductor will be assessed.         Anomalous low field magnetization in fine filament NbTi conductors    A. Ghosh, W. Sampson, E. Gregory and T. Kreilick Summary: The first cable conductors for SSC were made with NbTi filaments whose diameters were in the 18-23 micron range. In an effort to reduce the magnetization effects in accelerator dipoles resulting from these large filaments, second generation conductors are now being manufactured with much smaller filaments. As part of this development a series of NbTi conductors were made with filament diameters ranging from 8.0 to 2.8 /spl mu/m and having an average interfilament spacing of approximately 12% of filament diameter. Measurements at 4.3 K show that as the filament spacing decreases below a certain critical value the low field magnetization increases rapidly. This increase is seen to be strong function of interfilament distance, magnetic field and temperature. Details of these measurements and its implication for practical high current SSC wire design are discussed.         Superconducting properties of Cu-NbTi composite wires with fine filaments    K. Yasohama, K. Morita and T. Ogasawara Summary: Copper matrix NbTi wires with ultrafine filaments were fabricated by the multiple stacking technique, and the NbTi-filament diameter dependences of the critical temperature, the upper critical magnetic field and the critical current density were measured. The filament diameter ranged down to 0.008 /spl mu/m. As the diameter was reduced, the critical temperature began to decrease at a diameter of /spl sim/0.1 /spl mu/m. This depression was attributed to the proximity effect of the copper matrix on the NbTi filaments. The critical field measurement was carried out at 4.2 K under external magnetic fields applied both transverse and parallel to the wire axis. These critical fields were also lowered by the critical temperature depression due to the proximity effect. Furthermore, it was observed that the parallel critical fields were larger than the transverse ones. The critical current density at 4.2 K under the transverse magnetic field increased with decreasing filament diameter. This behavior was ascribed to the surface pinning at the boundary between the filaments and the matrix.         Calculation of AC losses in ultra fine filamentary NbTi wires    J. Cave, A. Fevrier, Hoang Ky and Y. Laumond Summary: The advent of Low loss Filamentary NbTi wires with very Fine Filaments, First developed hy Alsthom and the Laboratoires de Marcoussis, has led to the possibility of using superconductors in many AC 50/60 Hz applications. A computer program, based on the Bean Model, for any spacetime variation of the magnetic induction predicts losses successfully for filaments of diameter greater than /spl sim/1 /spl mu/m. However, for filaments of diameter less than /spl sim/1 /spl mu/m the theoretical calculation underestimates the losses dramatically. This is because the filament dimensions become comparable to /spl xi/, the coherence length, /spl lambda/ the magnetic penetration depth, a/sub 0/the flux line spacing and /spl lambda/, the pinning penetration depth leading to electromagnetic coupling effects between filaments. In this paper these effects on loss calculations are investigated with a view to obtaining an improved prediction of the loss behaviour in these materials. The results are consistent with a model of flux penetration, whereby, due to proximity effects, the matrix is essentially behaving as a type II superconductor. The main effect of this is to strongly couple flux lines in the first compaction bundles so that hysteretic losses in A.C. fields are greater than those predicted by the Bean Model.         AC losses in ultra-fine filament NbTi superconductors    A. Roovers, P. Fornerod, W. Heida and L. van de Klundert Summary: Loss measurements are presented on an ultrafine filament composite and on a regular AC conductor, having "thick" filaments. The wires have been subjected to an alternating transverse magnetic field. An AC as well as a DC transport current have been fed through the wires. The magnetic field and the AC transport current have been sinusoidal functions in phase. The magnetization losses and the transport current losses have been measured separately. The critical current - according to the 10/sup -14//spl Omega/m criterium - and the quality factor n - according to V = V/sub 0/(I/I/sub c/)/sup n/- have been determined.         Thermally induced pre-stress and critical current density of PbMo/sub 6/S/sub 8/wires    B. Seeber, W. Glaetzle, D. Cattani, R. Baillif and O. Fischer Summary: Powder-metallurgical processed PbMo/sub 6/S/sub 8/monofilamentary wires with a molybdenum-matrix suffer under a tensile pre-stress on the superconducting core which is due to a difference in the thermal expansion coefficient of the constituents. In this case the observed critical current densities may be up to two orders of magnitude smaller compared to bulk samples. We have now improved considerably the critical current density of PbMo/sub 6/S/sub 8/monofilamentary wires by a compressive pre-stress on the superconductor. This was achieved by developing a new hot extrusion and drawing technology based on a molybdenum stainless-steel matrix. J/sub c/is now in the range of 1x10/sup 8/A/m/sup 2/at 14 T and 4.2 K, which corresponds approximately to the value observed in PbMo/sub 6/S/sub 8/bulk samples. Lengths of up to 1 km of these wires have already been manufactured.         Fabrication, metallurgical characterization and superconducting properties of Pb- and SnMo/sub 6/S/sub 8/tapes    N. Sadakata, T. Kuroda, M. Suenaga and R. Sabatini Summary: Chevrel phase superconducting Pb- and SnMo/sub 6/S/sub 8/tapes were produced by a solid (Mo)-vapor (Pb or Sn and S) reaction process. The superconducting critical temperatures T/sub c/for the compounds, which were formed by this process, were 14.8 and 14.7 K with the transition width of 0.2 K for PbMo/sub 6/S/sub 8/and 0.5 K for SnMo/sub 6/S/sub 8/, respectively. The best superconducting critical current densities for the PbMo/sub 6/S/sub 8/tapes were 1.5x10/sup 8/A/m/sup 2/and 6x10/sup 7/A/m/sup 2/at 10 and 19 T, respectively. The dependence of T/sub c/on the processing conditions and the results of metallurgical characterization of these compounds are discussed.         Critical current densities and critical fields of AgMo/sub 6/S/sub 8/thin films    G. Hertel, T. Orlando and J. Tarascon Summary: Critical currents and upper critical fields were measured on reactively sputtered AgMo/sub 6/S/sub 8/films with critical temperatures of up to 9.2K. X-ray measurements on these films, which were grown on sapphire substrates held at temperatures between 800/spl deg/C and 1000/spl deg/C, show a preferential orientation of the grains with the 001 direction parallel to the surface of the substrate. The critical field in the perpendicular direction is about 11 tesla when extrapolated to zero temperature. Critical current densities 1x10/sup 8/A/m/sup 2/were obtained at 6 tesla and 1.2K. Polycrystalline AgMo/sub 6/S/sub 8/, prepared by annealing Ag/Mo multilayers in sealed quartz tubes which contain MoS/sub 2/powder, are used as a comparison to investigate the influence of crystalline order on the critical currents and critical fields of Chevrel phases. We find that although the critical field is larger for the polycrystalline sample, the critical currents are much larger for the preferentially oriented samples.         High field properties of SnMo/sub 6/S/sub 8/and PbMo/sub 6/S/sub 8/ribbons prepared using a vapor transport technique    D. Capone II, D. Hinks and D. Brewe Summary: Superconducting ribbons of SnMo/sub 6/S/sub 8/and PbMo/sub 6/S/sub 8/have been produced using a one step vapor transport technique. In this process Sn or Pb vapor and H/sub 2/S gas react at the surface of a Mo substrate at elevated temperatures to form a uniform coating of Chevrel phase. SEM micrographs show the film on the ribbons to be composed of small (/spl lsim/0.5 /spl mu/m) single-crystal rhombohedra of Chevrel phase. Critical currents for the SnMo/sub 6/S/sub 8/ribbons are similar to that achieved in PbMo/sub 6/S/sub 8/by other techniques (/spl sim/1 /spl times/ 10/sup 4/A/cm/sup 2/at 19 T and 4.2 K). The performance of our PbMo/sub 6/S/sub 8/is severely degraded. An explanation for this is based on larger intrinsic strain effects in the PbMo/sub 6/S/sub 8/.         Superconducting properties of Chevrel phase PbMo/sub 6/S/sub 8/wires produced by the powder process    H. Yamasaki and Y. Kimura Summary: We have fabricated Chevrel phase PbMo/sub 6/S/sub 8/wires by the powder process and observed a very high critical current density. SUS-Mo sheathed wires were made through hot-swaging and hot-drawing operations, and the PbMo/sub 6/S/sub 8/compound was formed from PbS, Mo and MoS/sub 2/mixed powders. We measured the critical current for a 27 cm long wire wound around a cylindrical specimen holder, and observed a very high J/sub c/value - 5.5x10/sup 4/A/cm/sup 2/at 8 T, calculated for the segment of the PbMo/sub 6/S/sub 8/compound. We have also investigated the influence of the preparation conditions upon the T/sub c/and -(dB/sub c2//dT) values of bulk samples, in order to know the appropriate synthesis conditions to obtain high T/sub c/and high B/sub c2/PbMo/sub 6/S/sub 8/compound in the wire.         Author Index (1986)    No author information available Summary: Not available

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