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1984     Front Cover (1984)    No author information available Summary: Not available         Table of Contents (1984)    No author information available Summary: Not available         Conference Information (1984)    No author information available Summary: Not available         Editorial (1984)    M. Green Summary: Not available         In memoriam (1984)    M. Lubell Summary: Not available         Highlights (1984)    No author information available Summary: Not available         Magnetic monopoles    D. Fryberger Summary: In this talk on magnetic monopoles, first I will briefly review some historical background; then, I will describe what several different types of monopoles might look like; and finally I will discuss the experimental situation.         An integration of all refractory Josephson logic LSI circuit    S. Kosaka, A. Shoji, M. Aoyagi, F. Shinoki, S. Tahara, H. Ohigashi, H. Nakagawa, S. Takada and H. Hayakawa Summary: An integration process for the fabrication of an all refractory Josephson LSI logic circuit is described. In this process, niobium nitride and niobium double-layered Josephson junctions were integrated using a reactive ion etching with a 2.5 /spl mu/m minimum feature. A highly selective and anisotropic RIE process and a planarizing technology have been developed for intagrating a circuit with LSI complexity. For evaluating the process capability, test vehicle circuits with MSI/LSI level complexity have been designed and fabricated using this process. An 8 bit ripple carry adder and a 4X4 bit parallel multiplier have been integrated with Josephson four junction logic ( 4JL ) gates, the largest of which contains more than 2800 Josephson junctions. Both functionality and high-speed performance testings have been successfully performed with these test circuits.         Josephson tunnel junctions with refractory electrodes    S. Raider Summary: Fabrication of high quality Josephson tunnel junctions with refractory electrodes is made difficult by the electrode's short coherence lengths and the sensitivity of the their superconducting properties to tunnel barrier processing. Several innovative procedures have been developed to address this problem. In this review, we describe these tunnel barrier processes and the junction characteristics that were obtained using them. In particular, attention is focused on the junction's subgap conductance and the reproducibility of the maximum Josephson current because of their importance as device design parameters for integrated circuits.         The role of Ar+, CH+/sub 4/, O+/sub 2/and backscattered Pb+ ions during Nb/Oxide/PbAuIn edge junction fabrication    P. Brosious Summary: A study has been made of the correlation between energetic positive plasma ions and the resulting Josephson tunnel barriers fabricated in an RF plasma. Typical edge junction current densities of 4000 Amp/cm/sup 2/and Vm's of 25 mV were achieved. An in-situ mass spectrometer system was designed to extract, energy analyze, and identify the positive ion species incident on the RF cathode/sample surface. The argon positive ion measurements are correlated to Nb sputter rates and back scattered Pb and Nb rates - required for a clean Nb interface. The CH/sub 4/positive ions are correlated to the growth of niobium carbide which reduces sub-oxide formation while optimizing junction quality. Finally the niobium oxide growth is correlated to the O/sub 2/positive ion measurements. A simple model for oxide growth consisting of a time dependent O+/sub 2/ion induced term and a time independent or very fast initial state term accounts for the known junction tunnel current dependencies on the RF plasma parameters of pressure, voltage, frequency, time, and ion to substrate angle.         Thermal cycling stability of lead-alloy Josephson junctions with double layer base electrodes    T. Imamura, S. Hasuo and T. Yamaoka Summary: In this paper, Josephson junctions with double layer base electrodes are proposed, and their thermal cycling stability is reported. The double layer base electrode has been made of a thick Nb lower film and a thin Pb-In-Au upper film prepared at 77K. The thermal cycling experiment has been carried out for 11780 junctions, and their excellent cycling stability has been observed.         Discrete lorentzian structure in low frequency voltage noise spectra of very small area Josephson tunnel junctions    C. Rogers and R. Buhrman Summary: We report the results of low frequency voltage noise measurements on very small area (A = 0.05 to 1 /spl mu/m/sup 2/) Nb-Nb/sub 2/O/sub 2/-PbBi tunnel junctions as a function of tunnel junction quality and over a wide range of voltage and temperature. We find that the noise spectrum S/sub v/in our bandwidth (1Hz to 25.6kHz) is largely composed of a small number (2-3) of distinct Lorentzian components each of which can be characterized by its own voltage and temperature dependent magnitude and mean rate. These lorentzian components provide a powerful means to probe the actual microscopic fluctuation events which lead to 1/f noise in larger devices. The ensemble average spectrum of our devices trends about a 1/f frequency dependence and has a magnitude proportional to (IR/sub J/)/sup 2/and 1/A. We have used our results to establish the intrinsic low frequency energy sensitivity of d.c. SQUIDs made with shunted tunnel junctions.         Influence of beam energy, flux, and composition on junction parameters in ion beam tunnel barrier processing    A. Kleinsasser Summary: An ion beam process was used to fabricate planar and edge-defined niobium-lead alloy Josephson junctions. Critical current density was found to be determined primarily by the dose of oxygen ions delivered during tunnel barrier growth. Comparison of spatial distributions of critical currents with ion flux profiles indicated that both preclean and oxidation were important in determining the magnitude of the on-wafer spatial variations. Uniformity of angle of incidence of the ion beam was very important in fabrication of edge junctions. The first ion beam experiments involving intentional additions of carbon-containing ions to the beam, to facilitate controlled growth of a carbide interfacial layer which is important in high quality devices, are also reported.         High field RF superconductivity: To pulse or not to pulse?    I. Campisi Summary: Experimental data on the behavior of superconductors under the application of RF fields of amplitude comparable to their critical fields are sporadic and not always consistent. In many cases the field level at which breakdown in superconducting RF cavities should be expected has not been clearly established. Tests conducted with very short (/spl sim//spl mu/s) RF pulses indicate that in this mode of operation fields close to the critical values can be consistently reached in superconducting cavities without breakdown. The advantages and disadvantages of the pulsed method are discussed compared to those of the more standard continuous wave (cw) systems.         High Q sapphire loaded superconducting cavities and application to ultrastable clocks    D. Blair and S. Jones Summary: This paper describes the microwave properties of a sapphire loaded super conducting cavity resonator. We report measurements of energy confinement, evanescent field scale lengths, and radiation losses. We report high quality factors, in excess of 10/sup 9/at cryogenic temperatures, for a resonator based on a sapphire element mounted inside a superconducting cavity. Resonators of this type have potentially valuable applications as ultrahigh stability oscillators, high Q filters and as low phase noise frequency sources.         Development of superconducting niobium accelerating structures for heavy ions    K. Shepard, S. Takeuchi and G. Zinkann Summary: Results of tests of two new designs for superconducting niobium resonant cavities are presented. Both types resonate at 145.5 MHz and accelerate most efficiently for particle velocities /spl beta/= v/c = 0.16. One resonator is of the split-ring type, but of a simpler design than a previously reported /spl beta/=.16 unit. Although the surface fields are higher, the performance is somewhat better than for the earlier design: an accelerating field E/sub a/= 4.3 MV/m has been obtained at 4.2K with 4w of rf input, where E/sub a/is defined as the energy gain per unit charge for a synchronous particle averaged over the interior resonator length. The other resonator is an 8-inch OD tapered coaxial quarter-wave line terminated with a drift tube of 1.50 inch aperture. At 4.2K, this resonator exhibits a low-level Q of 2x10/sup 9/, and has achieved E/sub a/= 4.7 MV/m with 2.8w of rf input.         Influence of thermal conductivity on the breakdown field of niobium cavities    H. Padamsee Summary: To experimentally check the predictions of the thermal model for the influence of thermal conductivity on breakdown field levels in Nb cavities, eight elliptical cavities at 8600 MHz have been built from material with RRRs of 25, 50 and 100 (RRR /spl alpha/ thermal conductivity). After several rf tests on each cavity, the RRRs were increased by outgassing at -2000 C in a vacuum of         Superconducting 500 MHz accelerating copper cavities sputter-coated with niobium films    C. Benvenuti, N. Circelli, M. Hauer and W. Weingarten Summary: Thermal breakdown induced either by electron loading or by local defects of enhanced RF losses limits the accelerating field of superconducting niobium cavities. Replacing niobium with a material of higher thermal conductivity would be highly desirable to increase the maximum field. Therefore, cavities made of OFHC copper were coated by D.C. bias sputtering with a thin niobium film (1.5 to 5 /spl mu/m). Accelerating fields up to 8.6 MVm/sup -1/were obtained without observing any field breakdown, the limitation being due to the available rf power. The Q values achieved at 4.2 K and low field were similar to those of niobium sheet cavities (i.e./spl sim/2 /spl times/ 10/sup 9/), but a fast initial decrease of Q to about 10/sup 9/was reproducibly experienced. Subsequent inspection of regions of enhanced rf losses revealed defects the origin of which is under study. The apparatus used for coating the cavities and the results obtained are presented and discussed.         Development of 12 T-10 Al-stabilized Nb/sub 3/Sn conductor for TMC-II    Y. Takahashi, T. Ando, T. Hiyama, H. Tsuji, E. Tada, M. Nishi, K. Yoshida, K. Okuno, K. Koizumi, H. Nakajima, T. Kato, K. Kawano, M. Oshikiri, Y. Hattori, R. Takahahi, S. Kamiya, Y. Ohgane and S. Shimamoto Summary: The Al-stabilized Nb/sub 3/Sn strand has been successfully fabricated and J/sub c/value of 400 A/mm/sup 2/at 12 T is obtained on condition that Nb/sub 3/Sn is reacted at 625/spl deg/C for 200 hr. Overall residual resistivity of this strand is lowered to 77 % of that of the Cu-stabilized Nb/sub 3/Sn strand (TMC-I)/sup 1,2/at 12 T by Al-stabilizer. The 12 T-10 kA cable-in-conduit conductor, fabricated by this strands, is charged up to 20 kA at 8.7 T without appearance of normal zone. From these experimental results, this conductor satisfies almost the specification of the present target conductor (TMC-II)/sup 3/.         The effects of low temperature fatigue on the RRR and strength of pure aluminum    K. Hartwig, G. Yuan and P. Lehmann Summary: Low temperature fatigue effects on residual resistivity ratio (RRR = /spl rho//sub 273 K/ / /spl rho//sub 4.2K/) and strength of 300 and 1000 RRR aluminum are reported. The objective of this investigation is to select the best initial purity for the stabilizer aluminum used in energy storage magnets. Monolythic centimeter diameter specimens were fatigued at 4.2 K to strains (/spl epsiv/) reaching 0.3 percent. The resistivity ratio rapidly decreases during the first 100 cycles and approaches saturation (RRR/sub f/) after about 1000 cycles for all strains tested. The RRR/sub f/values are different for different initial resistivity ratio (RRR/sub i/) values, but all tend to come together at 0.3% strain independent of RRR/sub i/. The maximum specimen stress (/spl sigma//sub max/) is reached after about 1000 cycles also, and approaches a common value (/spl sigma/ sub max/ = /spl epsiv/E/2, where /spl epsiv/ is the strain range and E the elastic modulus) independent of RRR/sub i/. Thus high purity aluminum becomes "fully hard" at equilibrium and behaves elastically. The impact of fatigue damage on conductor design and choice of stabilizer purity is considered.         Effect of the thermal barrier on the stability of cable-in-conduit conductors    T. Ando, Y. Takahashi, M. Nishi, E. Tada, K. Okuno and S. Shimamoto Summary: As the enhancement of stability margin of cable-in-conduit conductors, the effect of thermal barrier provided inside the surface of strand has been investigated. Firstly, by a simple model calculation, it is shown that the energy needed to raise the temperature of a strand as the simulation of the disturbance due to surface friction, depends strongly on the pulse duration and thermal conductivity of surface material. Next, as based on this consideration, strands with the thermal barrier inside its surface have been made and the stability test has been carried out. From the result, it was shown that the stability margin of a cable-in-conduit conductor consisting of strands with the thermal barrier can be calculated with the enthalpy of whole helium whithin the conduit even near the critical current.         Effect of a transport current on the losses of a superconducting composite under fast changing magnetic field    D. Ciazynski Summary: The behaviour of a superconducting composite carrying a transport current and subjected to a transverse fast changing magnetic field has been simulated with an equivalent electrical network. The problem of the current distribution inside the composite under steady-state conditions has been solved with a computer code which leads to the exact solution of Maxwell's equations. The total loss power inside the composite has been calculated and the loss power provided by the d.c. power-supply has been separated from the loss power provided by the magnetic field. These different losses can be easily compared with experimental data as they correspond to the different measured losses.         A.C. loss contributions of the transport current and transverse field caused by combined action in a multifilamentary wire    J. de Reuver, G. Mulder, P. Rem and L. van de Klundert Summary: A.c. losses caused by an a.c. transport current and a transverse a.c. magnetic field during simultaneous action were measured. The loss contributions have been obtained separately. The measurements were performed on a NbTi multifilamentary wire having a CuNi matrix of low conductivity in order to prevent eddy currents. The test configuration is presented and measurement results as well as theoretical confirmation are dealt with.         NbTi wires with ultra-fine filaments for 50 - 60 Hz use: Influence of the filament diameter upon losses    P. Dubots, A. Fevrier, J. Renard, J. Tavergnier, J. Goyer and Hoang Gia Ky Summary: For eighteen months, we have manufactured long lengths of multifilamentary superconducting wires, which comprise from several ten thousand to several hundred thousand 0.08 to 1 micron-diameter NbTi filaments. In these wires, the matrix between the filaments is made of pure CuNi and their structure provides a good magnetic stability and leads to strongly reduced 50 Hertz losses. Obtained results open very new prospects for applications of superconductivity in fast pulsed magnets and in A.C. current devices. In this paper we present results of 50 Hz loss measurements in these wires and we discuss the influence of the filament diameter upon these losses.         Signal processing: Opportunities for superconductive circuits    R. Ralston Summary: Prime motivators in the evolution of increasingly sophisticated communication and detection systems are the needs for handling ever wider signal bandwidths and higher data processing speeds. These same needs drive the development of electronic device technology. Until recently the superconductive community has been tightly focused on digital devices for high speed computers. The purpose of this paper is to describe opportunities and challenges which exist for both analog and digital devices in a less familiar area, that of wideband signal processing. The function and purpose of analog signal-processing components, including matched filters, correlators and Fourier transformers, will be described and examples of superconductive implementations given. A canonic signal-processing system is then configured using these components in combination with analog/digital converters and digital output circuits to highlight the important issues of dynamic range, accuracy and equivalent computation rate. Superconductive circuits hold promise for processing signals of 10-GHz bandwidth. Signal processing systems, however, can be properly designed and implemented only through a synergistic combination of the talents of device physicists, circuit designers, algorithm architects and system engineers. An immediate challenge to the applied superconductivity community is to begin sharing ideas with these other researchers.         Superconductive delay-line technology and applications    R. Withers, A. Anderson, J. Green and S. Reible Summary: Microwave analog signal-processing filters have been realized in the form of coupled niobium striplines on silicon dielectric substrates. Device responses with /spl plusmn/ 2-dB amplitude accuracy and 9/spl deg/-rms phase error have been achieved in amplitude-weighted filters with 37.5 ns of dispersion and 2.3-GHz bandwidths. Relative side-lobe levels of -26 dB and less are currently obtained. The achievable dispersion for stripline circuits on a single pair of 5-cm-diameter, 125-/spl mu/m-thick wafers is limited to about 40 ns by the electro-magnetic coupling between neighboring lines. To achieve greater dispersion two approaches are under development: (1) Stripline circuits are being fabricated on multiple wafer pairs which are physically stacked and electrically concatenated to produce dispersive delay lines with 4-GHz bandwidth and 75-ns dispersion time. Phenolic resin is used as an adhesive to ensure the mechanical integrity of the stacked structure. (2) A technique to fabricate dense stripline circuits on very thin (15-/spl mu/m) single-crystal silicon superstrates supported by thicker substrates has been demonstrated and preliminary results will be described. A chirp-transform system capable of real-time spectral analysis has been constructed using a pair of the superconductive delay-line filters. A resolution of 43 MHz over an unprecedented 2400-MHz bandwidth with amplitude uniformity of /spl plusmn/1 dB and side-lobe levels of -18 dB was demonstrated.         Superconductive convolver with junction ring mixers    S. Reible Summary: A superconductive convolver with tunnel-junction ring mixers has been developed and demonstrated as a programmable matched filter for near 1-GHz-bandwidth chirped waveforms. A low-loss, 14-ns-long superconductive stripline circuit provides temporary storage and relative shifting of signal and reference waveforms. These waveforms are sampled by 25 proximity tap pairs and local multiplication is performed by 25 junction ring mixers. Two short transmission lines coherently sum the local products and deliver the convolution output. The output power level of the convolver has been increased 18 dB by the incorporation of ring mixers and other output circuit improvements. These mixers employ series arrays of niobium/niobium oxide/lead junctions driven by delay-line taps in a quasi-balanced manner. The ring mixer provides higher output power levels (to -58 dBm), improved suppression of undesired mixing products and higher rf impedances than did the single-junction mixers used in the previous device. Convolvers can provide the essential programmable matched-filter component for extremely wide-bandwidth spectral analysis or spread-spectrum communication systems. The current device has a 2-GHz design bandwidth and a time-bandwidth (TB) product of 28. It produced compressed pulses with -7 dB peak-to-side-lobe levels. Design improvements to be discussed include increasing the TB product to 100 and reducing spurious side-lobe levels.         Superconducting A/D converter using latching comparators    C. Hamilton, F. Lloyd and R. Kautz Summary: This paper describes the design and performance of a six-bit A/D converter using fast edge latching comparators. Simulations predicting conversion times of 100 ps and 100 MHz signal bandwidth are verified experimentally. The addition of a superconducting track/hold circuit in front of the A/D converter is expected to substantially improve the signal bandwidth.         A high-speed analog-to-digital converter using Josephson self-gating-AND comparators    D. Petersen, H. Ko, R. Jewett, K. Nakajima, V. Nandakumar, J. Spargo and T. Van Duzer Summary: A Josephson Analog-to-Digital (A/D) converter which employs Self-Gating-AND (SGA) circuits as comparators has been designed and experimentally investigated. A functional description of the SGA is presented and the design of a four-bit A/D converter is described. High-speed measurements demonstrate four-bit quantization of 280 MHz sinusiodal inputs, and three-bit quantization of 499 MHz inputs at a 1.0 GHz conversion rate.         High speed non-latching SQUID binary ripple counter    A. Silver, R. Phillips and R. Sandell Summary: High speed, single flux quantum (SFQ) binary scalers are important components in superconducting analog-to-digital converters (ADC). This paper reviews the concept for a SQUID ADC and the design of an SFQ binary ripple counter, and reports the simulation of key components, and fabrication and performance of non-latching SQUID scalers and SFQ binary ripple counters. The SQUIDs were fabricated with Nb/Nb/sub 2/O/sub 2//PbIn junctions and interconnected by monolithic-superconducting transmission lines and isolation resistors. Each SQUID functioned as a bistable flip-flop with the input connected to the center of the device and the output across one junction. All junctions were critically damped to optimize the pulse response. Operation was verified by observing the do I-V curves of successive SQUIDs driven by a cw pulse train generated on the same chip. Each SQUID exhibited constant-voltage current steps at 1/2 the voltage of the preceding device as expected from the Josephson voltage-to-frequency relation. Steps were observed only for the same voltage polarity of successive devices and for proper phase bias of the SQUID. Binary frequency division was recorded up to 40GHz for devices designed to operate to 28GHz.         A general numerical analysis of the superconducting quasiparticle mixer    R. Hicks, M. Feldman and A. Kerr Summary: Virtually all analyses of the superconductor-insulator-superconductor (SIS) quasiparticle mixer have employed the quantum theory of mixing in its three-frequency approximate form. This approximation is valid only in the limit of very large junction capacitance. For finite capacitance, these analyses may be seriously in error. To remedy this, a computer program has been developed which uses the quantum theory of mixing in its most general form, treating the large-signal properties of the mixer in the time domain. The terminating impedances at the harmonics of the local oscillator frequency and their sidebands can be arbitrary. Using this analysis, the effect of finite junction capacitance on one SIS mixer's performance is described. This gives an insight into the range of validity of the three-frequency model.         Accurate noise measurements of superconducting quasiparticle array mixers    W. McGrath, A. Raisanen, P. Richards, R. Harris and F. Lloyd Summary: We have constructed a 30-40 GHz test apparatus which allows us to measure the noise temperatures of SIS mixers with an accuracy of better than /spl plusmn/1K. This is a factor of six improvement over earlier measurements. The most accurate measurement made thus far of a mixer which uses a single Pb-alloy junction yielded T/sub m/= 9.2 /spl plusmn/ 0.9 K; and mixer gain: G/sub m/= 0.240 /spl plusmn/ 0.005. In addition, SIS mixers employing arrays of N = 1, 5, 10, 25, and 50 tunnel junctions in series have been tested. The input power required to saturate the array mixers was found to increase as N/sup 2/and the gain and noise temperature of the array mixers were independent of N.         A planar antenna-coupled superconductor-insulator-superconductor detector    K. Irwin, T. Van Duzer and S. Schwarz Summary: In order to avoid the difficulties associated with waveguide and point contacts at frequencies above 100 GHz, a planar integrated circuit combining SIS junctions and a receiving antenna has been developed. The antenna pattern and a study of the quasi-optical coupling using an f/1 TPX lens are presented. Measurements of the direct detection performance of this device at 88 GHz agree well with quantum theory. The measured noise of the device gives an NEP of 5.6x10/sup -14/W//spl radic/Hz. The antenna can readily be scaled to higher frequencies where quasi-optical coupling is essential. Being planar, this device can be replicated into a multi-detector array for imaging.         Response of Nb-aSi-Nb junctions to 604 GHz radiation    W. Danchi, J. Free, F. Habbal, M. Tinkham and L. Smith Summary: We have measured the response of Nb-aSi-Nb junctions to 604 GHz radiation from an optically pumped far-infrared (FIR) laser source. These rugged and thermally cyclable junctions situated at the midpoint of 180 /spl mu/m long dipole antennas, were fabricated on oxidized silicon wafers using the Selective Niobium Anodization Process (SNAP). Josephson current densities were /spl sim/9,000 A/cm/sup 2/, the McCumber parameters /spl beta//sub c/were /spl sim/3.5, and the Josephson plasma frequencies /spl omega//sub J/ /spl sim/2.5/spl times/10/sup 12/. On a junction with a normal state resistance of /spl sim/7/spl Omega/, we observed three Josephson steps and one photon-assisted tunneling step. The widths of the Josephson steps were studied as a function of the laser power. An RSJ model computer simulation with a nonlinear quasiparticle conductance and an rf current bias (assumed because of the low junction resistance) is able to account reasonably well for the laser-power dependence of the critical current (zeroth step) and the second step. However, the temperature dependence is more complex, and a discrepancy still exists between the RSJ model calculation and the data for the hysteretic first step.         Fabrication and properties of high T/sub c/SNS microbridge series arrays    W. Anklam, A. de Lozanne and M. Beasley Summary: The fabrication and electrical Characteristics of series connected arrays of high critical-temperature SNS Josephson microbridges are described, the initial purpose of the investigation being the development of voltage standards and ultrastable voltage references operational above 10K. Using Nb/sub 3/Sn/Cu step-edge microbridges, arrays containing 15 and 39 bridges have been fabricated which operate up to 16.5K. The arrays are irradiated by an antenna producing voltage steps in the array's I-V characteristics in which all the bridges are simultaneously locked to the first Step.         A Josephson sampler with 2.1 ps resolution    P. Wolf, B. Van Zeghbroeck and U. Deutsch Summary: A Josephson sampler with 2.1 ps resolution is reported. The sampler was made with Nb edge junctions, and consists of a sampling junction to which a Faris pulser is coupled directly. Two experiments are connected to the sampler: a two-junction interferometer and another Faris pulser. A new and simple electronic delay allows a flicker-free display on an oscilloscope of the waveform sampled. A current sensitivity of 0.8 /spl mu/A was achieved. It was possible to measure the switching transitions of the two-junction interferometer over its whole vortex boundary, including vortex-to-vortex transitions which occur at low bias currents. To our knowledge, this is the fastest Josephson sampler made to date.         An application of picosecond electro-optic sampling to superconducting electronics    D. Dykaar, T. Hsiang and G. Mourou Summary: A picosecond electro-optic sampling technique has been used to measure the switching threshold of a single tunnel junction in a coplanar transmission line geometry. The optical system used, a colliding-pulse mode-locked laser, generated two 120 fs FWHM at 100 MHz. One pulse was used, via a photoconductive switch, to generate an electrical signal of adjustable height and width. The second pulse was used to detect the electrical transient by probing the change in the birefringence of a lithium tantalate crystal induced by the electrical signal. This optical sampling scheme had intrinsic temporal and voltage resolutions of < 500 fs and < 1 mV. In actual experiments, the connection-limited time resolution was 55 ps or 16 ps, depending on whether the detector was placed in room or cryogenic environment. The measured response of the tunnel junction was found to be consistent with the RSJ model.         Experience highlights from the design and manufacture of U.S. LCT coils    R. Kibbe, C. Amonett, R. Benson, R. Hussung and W. Shipley Summary: The international Large Coil Task (LCT) is a major activity in the development of superconducting toroidal field (TF) coils for tokamak fusion reactors. The technical objective of this program is to design, build, and test six large TF coils, thereby producing information and data that can be used directly by program planners and designers of tokamak reactors. After an intensive competetive bidding cycle, contracts were awarded in 1977 to three U.S. industrial firms for the design and manufacture of test coils. Subsequently Japan, EURATOM, and Switzerland agreed to supply one coil each. External dimensions and minimum performance requirements are identical but freedom was allowed in the choice of internal design and manufacturing techniques. All six coils will be tested in a compact toroidal array in the Large Coil Test Facility (LCTF) in Oak Ridge, Tennessee. With the coil fabrication phase approaching completion, it is an appropriate time to review the major technical challenges and lessons from the design and manufacture of the three U.S. LCT coils.         Preliminary results of the partial-array LCT coil tests    J. Luton, F. Cogswell, L. Dresner, J. Ellis, W. Fietz, G. Friesinger, W. Gray, Y. Iwasa, K. Koizumi, M. Lubell, J. Lue, J. May, M. Nishi, S. Peck, S. Schwenterly, S. Shen, R. Stamps, R. Takahshi, P. Walstrom, C. Wilson, R. Wintenberg, K. Yoshida and J. Zichy Summary: The Large Coil Task (LCT) is a collaboration between the US, Euratom, Japan, and Switzerland for the production and testing of 2.5 X 3.5 m bore, superconducting 8-T magnets. The definitive tests in the design configuration, the six coils arrayed in a compact torus, will begin in 1985. Partial-array tests are being done in 1984. In January the initial cooldown of two coils was aborted because of helium-to-vacuum leaks that developed in certain seal welds when the coil temperatures were 170 to 180 K. In July three adjacent coils (designated JA, GD, CH) were cooled, and in August two were energized to the limits of the test facility. An overview of the results is presented, including facility, cooldown, energization, dump, recovery from intentional normal zones, strain, and displacement, for operation up to 100% of design current but below full field and stress. These initial results are highly encouraging.         The Swiss LCT-coil    G. Vecsey, I. Horvath, B. Jakob, K. Kwasnitza, C. Marinucci, P. Weymuth, J. Zellweger, J. Zichy, H. Benz, A. Koch, F. Konig, R. Maix, H. Marti, J. Rauch, Th. Roman and A. Segessemann Summary: With delivery of the coil to ORNL on February 4, 1984, the second phase of the Swiss Large Coil Program - design and construction - was terminated. Mainlines of the Swiss design concept are summarized and related to theoretical calculations, experimental results of the supporting program, fabricational experience and first successful test results. An attempt is made to draw preliminary conclusions with regard to the design of future toroidal systems such as NET.         Instrumentation and test of the Swiss LCT-coil    J. Zichy, G. Vecsey, I. Horvath, B. Jakob, C. Marinucci, P. Weymuth and J. Zellweger Summary: Just before Christmas 1983 the fabrication of the Swiss LCT-coil was finished. Tests at ambient temperature were performed on the factory site and after delivery in Oak Ridge. To avoid an undesirable delay of the rescheduled Partial-Array Test it was agreed to install The coil without its superconducting bus. In July 1984 the Swiss LCT-coil was successfully cooled down to LHe temperature together with the other two fully installed coils. Besides the cooling system, the instrumentation, measured parameters of the coil and some preliminary results obtained during the ongoing Partial-Array Test are presented.         Results of the test of the European LCT coil in the TOSKA facility    W. Herz, H. Katheder, H. Krauth, G. Nother, U. Padligur, K. Rietzschel, L. Siewerdt, M. Susser, A. Ulbricht, F. Wuchner and G. Zahn Summary: The forced flow cooled European LCT coil was tested successfully as a single coil in the Karlsruhe test facility TOSKA. Operation at design conditions (10 kA, 5.6 T at 4.8 K and 6 bar) was achieved without any problems. Cryogenic, mechanical and electrical performance was in agreement with predictions. Due to the high stability, the coil could be operated close to its critical parameters by heating the supercritical helium up to about 6 K. The coil stayed superconducting even after a fast dump (7 s) from full current. Good performance is also expected for operation in the 6 coil toroidal array of the LCTF.         Stability of the TESPE superconducting torus magnets    K. Jungst and L. Yan Summary: Our laboratory size superconducting compact torus TESPE was tested in a symmetrical 3-coil arrangement of 3.5 MJ stored energy. The magnet system applying a superconductor of Cu/NbTi < 2:1 reached its design current of 7 kA in the first run. From the experimental investigations performed we select here an extensive study of stability over the total range of operating currents corresponding to values of the normal state heat generation per unit cooled surface from 0 to as high as 13.5 W/cm/sup 2/applying two heaters of different length and position. When a 17 cm long heater was used three stability regions following one to each other with increasing current have been observed. The experimental results are compared with the three stability theories: Maddock's equal area theory, Wilson's MPZ/Cold-End theory and Iwasa's CCM theory. Our experimental results and their analysis have led us to a combination of the existing theories with the normal state heat generation as discriminating parameter giving a complete description of the stability behaviour of bath-cooled magnets.         Towards a microstructural description of the superconducting properties    D. Larbalestier Summary: A discussion is provided of the state of our microstructural knowledge about filamentary Nb-Ti and Nb/sub 3/Sn conductors. The situation is believed to be much clearer for Nb-Ti than for Nb/sub 3/Sn, due to recent successes in elucidating the microstructures of Nb-Ti composites by TEM. Considerable changes in some earlier ideas of flux pinning are proposed and some semi-quantitative measures of precipitate flux pinning in Nb-Ti alloys are described. The situation is less advanced for Nb/sub 3/Sn. The J/sub c/is controlled by a greater number of variables and it is in general not clear that individual microstructural measurements can be taken to be typical of the whole composite.         High critical current densities of multifilamentary Nb- 46.5w%Ti superconductors    J. Somerkoski, L. Laakso, V. Vanhatalo, R. Toivanen and V. Lindroos Summary: Multiple heat treatment, critical current measurements and transmission electron microscopy were employed in improving the critical current carrying capacity of multifilamentary Nb-46.5w%Ti superconductors. The critical current density measurements at 4.2 K exhibited the values of 2860 A/mm/sup 2/and 580 A/mm/sup 2/at magnetic fields of 5 T and 9 T, respectively. The high current carrying capacity of the 5 times heat treated superconductor has been attributed to the improved size distribution of the effective pinning sites.         High critical current densities in industrial scale composites made from high homogeneity Nb 46.5 Ti    D. Larbalestier, A. West, W. Starch, W. Warnes, P. Lee, W. McDonald, P. O'Larey, K. Hemachalam, B. Zeitlin, R. Scanlan and C. Taylor Summary: Recent work in our group on the fabrication microstructure super conducting properties of composites of Nb-Ti has produced much new information about the procepitate morphology an orgins of high critical current density (J/sub c/) in ther materials. Precipitation of Ti-rich phase is seen to commence as a frain boundry film 2-4nm thick, the film then developing into approximately equiaxed particales of a /spl alpha/-Ti at the boundary triple points.         Temperature and field dependence of critical currents in V/sub 3/Ga wire produced by the MJR technique    T. Francavilla, D. Gubser and C. Pande Summary: The temperature dependence of V/sub 3/Ga multifilamentary wire produced by the modified jelly roll technique is reported as a function of applied magnetic field in the range 10K - 14K and 0-13T. Parameters which relate J/sub c/to H at 4.2K were found to apply at these temperatures and fields. The form of the temperature dependence of the critical current density is compared with theory.         Manufacturing of titanium-bronze processed multifilamentary Nb/sub 3/Sn conductors    K. Kamata, H. Moriai, N. Tada, T. Fujinaga, K. Itoh and K. Tachikawa Summary: It has been revealed that small amount of titanium addition to the bronze matrix is most effective for improving the high-field current-carrying capacities of bronze-processed multifilamentary Nb/sub 3/Sn conductor. Multifilamentary Nb/Cu-7.5 at %Sn-0.4 at %Ti round wires with 4-5 /spl mu/m-diam 31X331-cores fabricated through drawing process only showed the overall critical current density J/sub c/(overall) over 3.5x10/sup 4/A/cm/sup 2/at 15 T after the heat treatment at 690/spl deg/c for 200 hr. It was also shown that the critical current anisotropy became larger with increasing aspect ratio of the rectangular shaped multifilamentary Nb/Cu-7. 5Sn-0.4Ti conductors. Rectangular shaped 5 /spl mu/m-diam 31 X 361-core Nb/Cu-7.5Sn- 0.45Ti conductors prepared through double extrusions showed about the same tendencies in the aspect ratio dependence of I/sub c/(H/sub parallel) as those prepared through drawing process only, after the heat treatment at 690/spl deg/C for 200 hr. 9.5 mm wide and 1.8 mm thick Nb/Cu-7.5Sn-0.4Ti conductors with 5 /spl mu/m-diam 349 X 361-cores have been successfully fabricated in full production scale through three steps hydrostatic extrusion process. These rectangular shaped practical multifilamentary Ti bronze Nb/sub 3/Sn conductors make feasible to generate a central magnetic field over 16 T in the 190 mm winding inner diameter intermediate coil of the 18 T superconducting magnet at NRIM.         Comparison of superconducting properties and residual resistivities of bronze processed Nb/sub 3/Sn wires with Ta, Ti and Ni+Zn additives    E. Drost, W. Specking and R. Flukiger Summary: Critical current densities up to 23 T measured on a series of 19 core Nb/sub 3/Sn wires with Ta, Ti and Ni+Zn additions, prepared by the bronze route under identical conditions, show very similar results in the whole field range. After optimization, J/sub c/in the A15 layer was determined to 6x10/sup 4/A/cm/sup 2/at 18 T, independent on the alloying element. Parallel to the increase of J/sub c/at high fields, an enhancement of B*/sub c2/up to 26 to 27 T as well as a reduced strain sensitivity of J/sub c/with respect to unalloyed Nb/sub 3/Sn wires were observed in all cases. On fully reacted filamentary tapes of a/spl ap/10 /spl mu/m thickness and /spl ap/100/spl mu/m width (obtained from the same starting material) an increase of the residual resistivity from /spl rho//sub o/ = 16 /spl mu//spl Omega/cm for binary Nb/sub 3/Sn to 35 - 40 /spl mu//spl Omega/ cm for Ta alloyed Nb/sub 3/Sn (4 at%) was found. The present data are the first direct indication for the increase of /spl rho//sub o/in alloyed multifilamentary wires prepared by the bronze route. They furnish a strong evidence for the correlation between /spl rho//sub o/and the enhancement of B/sub c2/in alloyed Nb/sub 3/Sn wires.         Controlled precompression in Nb/sub 3/Sn conductors by internal reinforcement with a nonmagnetic steel/molybdenum composite    R. Flukiger and A. Nyilas Summary: Searching for an adequate nonmagnetic material for the internal reinforcement of Nb/sub 3/Sn conductors submitted to large Lorentz forces, the combination Molybdenum + 316 LN steel (austenite stabilized by nitrogen) has been investigated as a model material. It was found that a reinforcement by Mo alone leads to a complete compensation of the precompression on the Nb/sub 3/Sn filaments exerted by the bronze, thus leading to higher I/sub c/values. The gradual substitution of Mo by 316 LN steel leads to a decrease of B*/sub c2/from 21 T to 16 T, thus reflecting the dominant influence of the reinforcing material (<10 Vol. %) on the precompression. By changing the Mo : steel ratio, the value of /spl epsiv//sub m/; of the conductor can be set at any design value between 0 and 0.9%. Due to the ductile-to-brittle transition at low temperatures, the application range of Mo is, however, limited. A possible alternative, austenitic Mn steels with low thermal expansion coefficient are proposed.         An in depth characterization of (NbTa)/sub 3/Sn filamentary superconductor    D. Hampshire, H. Jones and E. Mitchell Summary: Further to our programme of investigations of new, technical superconductive materials which are of interest to designers of practical devices, we present the results of a detailed study of the critical parameters of the ternary addition A.15 material (Nb7.Sw/oTa)/sub 3/Sn manufactured by Vacuumschmelze GMBH, Hanau F.R.G. The basis of the results we report is a comprehensive Jc(B, T) characterization within the range, O         An overview of the IGC Internal Tin Nb/sub 3/Sn conductor    B. Zeitlin, G. Ozeryansky and K. Hemachalam Summary: We discuss the current state of the art in the IGC Internal Tin Nb/sub 3/Sn process which routinely is delivering current densities greater than 1x10/sup 3/A/mm/sup 2/at 10 Tesla. We focus especially on the conductors suitability for high current density applications such as High Energy Physics and small magnets. Projections are also made as to its suitability for high field applications such as in Fusion. A discussion of the manufacturing process is given with comparisons made to other accepted Nb/sub 3/Sn processes and NbTi. Superconductor characteristics such as filament quality and Nb/sub 3/Sn phase uniformity are compared to those obtained in conventional bronze process.         The critical current density and microstructural state of an internal tin multifilamentary superconducting wire    D. Dietderich, J. Glazer, C. Lea, W. Hassenzahl and J. Morris Summary: The critical current density (J/sub c/) of internal tin wires is increased when low-temperature diffusion heat treatments are performed prior to a high temperature reaction. To determine the variation of J/sub c/with pre-reaction heat treatments a copper-stabilized IGC internal tin wire with an outside diameter of 0.267mm was studied. The wire has 2 to 2.5 /spl mu/m diameter filaments, and within the Ta barrier, the area ratio of the copper matrix and Sn core to Nb is about 2.2. Due to the character of the Cu-Sn phase diagram, heat treatments at a series of temperatures below the Nb/sub 3/Sn reaction temperature affect the local Sn concentration in the matrix about the Nb filaments. The variation in J/sub c/resulting from these heat treatments is a consequence of the microstructural state of the conductor and the morphology of the Nb/sub 3/Sn layer produced. The results of this work show that the internal tin and bronze-processed wires have different J/sub c/(H) characteristics. The two processes have comparable critical currents at high fields, suggesting the same H/sub c2/, while at low fields the internal tin wire is superior, suggesting a better grain morphology.         Improvements in critical current densities of internal tin diffusion process Nb/sub 3/Sn wires by additions of third elements    K. Yoshizaki, M. Wakata, S. Miyashita, F. Fujiwara, O. Taguchi, M. Imaizumi and Y. Hashimoto Summary: Improvements in critical current densities of internal tin diffusion process Nb/sub 3/Sn multifilamentary wires have been attempted by indium and titanium additions. The Nb/sub 3/Sn wires with the indium addition to the Sn core and the titanium addition to the Cu matrix have been fabricated. The indium addition increases critical current density (Jc) at each field compared with pure Nb/sub 3/Sn wire, and Jc at higher fields increases with increasing filament diameter. An overall Jc of 6.2x10/sup 4/A/cm/sup 2/at 12T and 4.2K is obtained for the 4.2 /spl mu/m-filament indium addition wire reacted at 750/spl deg/C-50h. The titanium addition increases the Nb/sub 3/Sn layer growth rate and Jc in fields over 13T. An overall Jc of 3.0x10/sup 4/A/cm/sup 2/at 15T and 4.2K is obtained for the 11.7 /spl mu/m-filament titanium addition wire. Moreover, the simultaneous indium addition to the titanium addition wire produces further improvement in Jc. The indium and titanium addition Nb/sub 3/Sn wires are the most favorable superconductors for generating magnetic field over 10T.         Properties of Ti alloyed multifilamentary Nb/sub 3/Sn wires by internal tin process    M. Suenaga, C. Klamut, N. Higuchi and T. Kuroda Summary: Influence of Ti addition to the Sn core on the critical current density J/sub c/of multlfilamentary Nb/sub 3/Sn wires fabricated by the internal tin process was studied. The addition ( /spl sim/1.5 wt% Ti) improved the values of J/sub c/at very high magnetic fields over those for the pure Nb/sub 3/Sn, e.g., J/sub c/ /spl sim/140 A/mm/sup 2/at 18 T. This is 3-4 times greater than a similarly processed pure Nb/sub 3/Sn wire and is within /spl sim/10 % of the highest critical current density measured for the Ti alloyed bronze processed Nb/sub 3/Sn wires.         A combination bronze-in situ process for preparation of superconducting wire    J. Verhoeven, E. Gibson, J. Ostenson and D. Finnemore Summary: Superconducting Nb/sub 3/Sn-Cu wire has been prepared by placing rods of Cu-60 wt.% Nb in situ material in a bronze matrix and reducing to wire. The J/sub c/values of the wire are lower than that of commercial bronze processed wire by a factor of 2, which is consistent with the fact that the Br/Nb ratio is higher then commercial wires by roughly a factor of 2. It is anticipated that these bronze-in situ wires may display smaller degradation of J/sub c/with mechanical strain than conventional bronze processed wire.         Fabrication and performance of in-situ processed Nb/sub 3/Sn tape and multistrand wire    H. Ohkubo, M. Kodera, T. Noguchi, T. Kumano, M. Ichihara, E. Suzuki, K. Yasohama, H. Okon, K. Yasukochi and H. Hirabayashi Summary: A tape conductor and a multistrand wire, each of which has two different types, have been fabricated in long lengths. Nb/sub 3/Sn filaments of one type of the tape conductor are twisted. A pancake magnet (46 mm inner and 80 mm outer winding diameter) has been made of those tape conductors and tested in backup field of 7.5 Tesla. The tests have revealed that the twist improves stability of the tape conductor. Total magnetic field of 9.8 T was achieved using the tape with twisted Nb/sub 3/Sn filaments for windings of end pancake modules. Both types of the tape were made by external tin diffusion method and have critical current capacities of 240 Amp at 10 Tesla. The multistrand wires were manufactured by tin cored internal diffusion method. One type containes single tin core, the other type seven tin cores. The single and seven tin-cored wires have been successfully drawn to diameters of 0.62 and 1.26 mm respectively. Critical current densites of those wires were found to be (1.4 /spl sim/ 2.0) /spl times/ 10/sup 4/Amp/cm/sup 2/at 11 Tesla.         Properties and performance of the multifilamentary Nb/sub 3/Sn with Ti addition processed by the Nb tube method    S. Murase, H. Shiraki, M. Tanaka, M. Koizumi, H. Maeda, I. Takano, N. Aoki, M. Ichihara, E. Suzuki, K. Noto, K. Watanabe and Y. Muto Summary: MF Nb/sub 3/Sn conductors made by titanium added niobium tube process have been developed for use in high fields. Composites, consisting of Nb-1. Owt.%Ti tube with a copper sheathed tin core inside and a high conductivity copper tube outside, were stacked together up to 264 filaments, then drawn to the final sizes without any intermediate annealings. As workability was further improved by the titanium addition, it was possible to decrease the Cu/SC ratio for the conductor down to 0.67 and to increase the tin concentration up to 30 wt.% in Cu-Sn inside the filament. An enhanced layer growth rate and a slightly increased grain size of Nb/sub 3/Sn were observed in the titanium added conductors. compared with those made by use of pure Nb tube. The critical current density at high fields, which was more sensitive for heat-treatment condition, was superior to that of the other conventional processed conductors. Especially, the conductors with 30 % tin content have high critical current density for Nb/sub 3/Sn layer and an excellent field dependence of critical current density without copper: 1550 A/mm/sup 2/at 10 T, 600 A/mm/sup 2/at 15 T and 350 A/mm/sup 2/at 17 T. The critical current was also measured in the temperature range 1.88 - 4.2 K. A coil, aiming at 14 T, was fabricated using the conductor with .25 % tin to assure high level performance in practical situations.         Multilayer Nb/sub 3/Sn superconducting shields    D. Gubser, S. Wolf, T. Francavilla, J. Claassen and B. Das Summary: Multilayer Nb/sub 3/Sn shields have been designed, fabricated, and tested for use in low field, e.g. superconducting electronics, applications. Magnetic field profiles, shielding factors, and thermal effects are reported for these shields. The quality of the shields depends strongly on the reaction temperature used to form the Nb/sub 3/Sn layers with lower reaction temperatures forming better quality shields. Nearly ideal behavior was observed with a reaction temperature of 750/spl deg/C.         The manufacture of corrugated copper tubes with a Nb/sub 3/Sn layer    G. Meshchanov, I. Peshkov, G. Svalov, P. Rohner and G. Ziemek Summary: Based on prior experience gained with superconducting materials, further research work was jointly carried out by our organizations. The purpose of this effort was the establishment of a production process for the manufacture of corrugated, high-purity copper tubes incorporating the thickest possible layers of superconducting Nb/sub 3/Sn. The goal of the production process was to develop a corrugated, bendable superconductor as the core of a cryogenic envelope capable of withstanding reeling and unreeling on reels with barrel diameters up to 3 m, without damaging the brittle Nb/sub 3/Sn layer. The manufacturing process is described in detail. The latest results show a superconductor with a critical temperature of 15.5 K, having a 10 micrometer layer of pure Nb/sub 3/Sn, While not completely homogeneous, the sample is capable of carrying currents up to 125 - 140 A on a 10 mm sample width and in a magnetic field of 5 T. The corrugated tube acts at the same time as a self-compensating helium circuit and as the copper-stabilized current-carrying superconductor of a three-phase cable in a flexible cryogenic envelope. The envelope consists of four concentric corrugated tubes with an intermediate nitrogen shield. The resulting losses into the helium circuit are less than 0.2 Wm/sup -1/. The experiments have been conducted, until now, on tube lengths up to 40 m. All steps were carried out on conventional, commercially available equipment.         Magnetization measurements on multifilamentary Nb/sub 3/Sn and NbTi conductors    A. Ghosh, K. Robins and W. Sampson Summary: The effective filament size has been determined for a number of high current Nb/sub 3/Sn multifilamentary composites. In most cases it is much larger than the nominal filament size. For the smallest filaments (/spl sim/ 1 micron) the effective size can be as much as a factor of forty times the nominal size. Samples made by the "internal tin", "bronze route", and "jelly roll" methods have been examined with filaments in the range one to ten microns. Rate dependent magnetization and "flux jumping" have been observed in some cases. NbTi composites ranging in filament size from nine to two hundred microns and with copper to superconductor ratios between 1.6:1 and 7:1 have been examined in the same apparatus. Low field "flux jumping" was only observed in conductors with very large filaments and relatively little stabilizing copper.         Magnetic hysteresis and complex susceptibility as measures of ac losses in a multifilamentary NbTi superconductor    R. Goldfarb and A. Clark Summary: Magnetization and ac susceptibility of a standard NbTi superconductor were measured as a function of longitudinal dc magnetic field. The ac-field-amplitude and frequency dependences of the complex susceptibility are examined. The magnetization is related to the susceptibility by means of a theoretical derivation based on the field dependence of the critical current density. Hysteresis losses, obtained directly from dc hysteresis loops and derived theoretically from ac susceptibility and critical current density, were in reasonable agreement.         Critical current anisotropy in NbTi cables    M. Garber and W. Sampson Summary: The short sample critical current of multifilamentary NbTi cables is usually measured in a magnetic field which is oriented perpendicular to the broad face of the cable. This is the same orientation that occurs at the equatorial turns of a cos /spl theta/ type dipole magnet an is, therefore, usually specified in quality control short sample tests.         Experimental determination of stability margin in a 27 strand bronze matrix, Nb/sub 3/Sn cable-in-conduit conductor    J. Minervini, M. Steeves and M. Hoenig Summary: A small coil of internally cooled cabled superconductor was fabricated for experimental determination of the stability margin. The conductor is 27 strands of Nb/sub 3/Sn in a bronze matrix. The sheath material is JBK-75 superalloy. The bifilar coil was potted in epoxy in the annulus of a pulse coll set. Experimental results are presented defining critical pulse energy as a function of normalized operating current and background field. The relationships between dB/dt, pulse energy and stability margin are derived by calculation and confirmed by experimental calibration.         Comparison of long and short sample critical currents in Incoloy 903 Nb/sub 3/Sn cable-in-conduit conductors    M. Steeves, M. Hoenig and C. Cyders Summary: Measurements of critical currents on 330 cm long, 27 strand Nb/sub 3/Sn ICCS conductors indicate that compaction to 32% helium fraction in Incoloy 903 conduits does not degrade critical current. Short and long sample critical currents at 4.2 K and 1.5 /spl mu/V/cm for fields from 8 to 12 T were taken to determine how well short samples predict long sample performance. Samples were made from two separate untested 27 strand cables of Oxford Airco bronze matrix Nb/sub 3/Sn wire encapsulated in Incoloy 903 conduits; the cables were assumed to be identical. Voltage taps were spaced at approximately 2 cm for short samples and 330 cm for long samples. It was found that all samples were at the same state of strain. In two out of three cases, the critical currents of short samples matched those of long samples within 10%. In one case, mechanical damage to a long sample reduced its critical current relative to short samples from the same cable. Samples from the two otherwise identical cables did not yield identical critical currents, a result found to be due to different degrees of cable prereaction. Short samples are concluded to be good predictors of long sample performance as long as both have the same state of strain, the same state of prereaction, and are free of significant mechanical damage.         Transient heat transfer from a cable in conduit configuration in subcooled He I and He II    Z. Chen and S. Van Sciver Summary: Experimental investigations of liquid helium heat transfer from a model of a cable in conduit conductor are reported. The model consists of a 19 element stainless steel tubing bundle contained within a rectangular cross section conduit. The experiment involves resistively heating the bundle with a constant amplitude heat pulse, while recording the time variation of the temperature within the conductors and helium. Three test sections were studied each having a different spacing between the elements, /spl delta/. Results reported here are for bath temperatures 4.2, 2.5 and 1.8 K with applied pressure p : 100 kPa (1 atm).         High critical current density with low current sharing in a multifilament Nb55w/oTi superconductor    P. Bach and A. van Wees Summary: The Ti-rich NbTi-multifilament superconductor with a high current density at low fields and low current sharing properties is particularly well suited for application in NMR-magnets. In order to improve the performance of this kind of superconductors a number of Cu-billets with 54 filaments Nb55w/oTi have been extruded in a 1.4 GPa hydrostatic extrusion press. By subsequent cold area reduction and final precipitation heat treatment high critical current densities at low fields are obtained with very low current sharing (J/sub c/= 5.8 * 10/sup 9/A/m/sup 2/at 2T). TEM-investigations reveal a high density of small disc-like /spl omega/-Ti precipitates (Ptt. Density /spl sime/2/spl times/10/sup 22/m/sup -3/). The /spl omega/-Ti precipitates with a special orientation relationship relative to the /spl beta/-matrix are situated on specific crystallographic planes inside the subbands. This is different from the /spl alpha/-Ti precipitation in subband walls observed by other investigators in conventionally extruded and optimized NbTi-superconductors.         Surface currents in fine superconducting filaments    W. Carr Jr. Summary: Measurements were made of the magnetic moment observed in a fine filament NbTi superconductor upon cooling through the transition temperature in a magnetic field large compared with H/sub c1/. A partial Meissner effect was observed and this effect is interpreted in terms of surface current, body current and the magnetic moment of the flux lines. The interpretation is used to study the surface current behavior.         Behaviour of a NbTi very fine filament composite with current feed in the technical range    M. Asdente, V. Ottoboni, G. Ripamonti and S. Zannella Summary: Self-field losses have been measured on a NbTi multifilamentary wire with very fine filaments suitable for use in ac superconducting equipment working at industrial frequency. The loss trends as functions of current intensity and frequency as well as the comparison of the losses in a coil show that they are essentially of hysteretic nature.         Critical current and stability effects between 0 and 6 tesla in mono and multifilamentary NbTi conductors having a CuNi matrix    H. ten Kate, A. Roovers and L. van de Klundert Summary: We investigated the current carrying capacities of ten NbTi superconductors having a CuNi matrix with diameters between 50 and 300 /spl mu/m as function of an applied magnetic field of 0 to 6 tesla. The effects of the method of wire fixation and the electrical connections were studied. The results are compared to those obtained with two common conductors with Cu matrix. We observed large differences of a factor 2 between the critical current densities of the various CuNi matrix conductors. Furthermore, it is remarkable that the best CuNi matrix conductors have critical current densities which are much higher than those in Cu matrix conductors.         Experimental investigation of the loss characteristics of superconductors for AC power applications    F. van Overbeeke, K. Oordt and L. van de Klundert Summary: Recent studies confirm the economical feasibility of the application of superconductors in AC power apparatus. The low-loss conductor which has been proposed still only exists in theory. Simple calculations show that the economic criterion described by Ogasawara and Hlasnik is inaccurate because of an oversimplified hysteresis loss formula. A necessary modification shows that stricter demands will have to be made. As production of ultrafine filaments is a big technological problem, final diameter reduction by rolling instead of drawing is proposed. The expected better performance of a rolled composite has been verified experimentally in test coils as well as in transformer geometry. Experimental set-up and results are presented.         Stability of high-current-density composite superconductor subject to pulsive and local disturbance    O. Tsukamoto and M. Nakada Summary: The stability of high-current-density composite superconductors subject to pulsive and local disturbances are analyzed for various values of super to normal metal ratioes and overall conductor current densities. The stability of high-current-density superconductors subject to pulsive disturbances greatly depends on the heat transfer characteristics in the transient nucleate boiling region. In the analysis, we used the transient heat transfer data which we measured by using a brass foil heater with a Au-Fe vs. Cr thermocouple for measuring the temperature of the heater. It is shown that the most effective way to improve the stability of high-current-density composite conductors is to increase the current margin.         Destruction of superconductivity in current carrying NbTi fibers by strain energy    L. Wright, H. Wiederick and T. Hutchison Summary: Individual thin fibers of NbTi (46.5 wt % Ti) have been driven from the superconducting to the normal state by tensile force while immersed in liquid helium and carrying subcritical currents. The additional force for successive excursions from the superconducting to the normal state has been measured and found to saturate. This "mechanical training" can be reduced to the starting state for a fiber while at zero load by exceeding the critical current. Estimates are made of the mechanical energy to initiate quenching and since the tensile machine is "hard" estimates have also been made of the rise in temperature while subjected to short bursts of current greater than critical. There would appear to be structural changes which are stress level dependent and of a "shape memory" nature.         Epoxy cracking in the epoxy-impregnated superconducting winding: Nonuniform dissipation of stress energy in a wire-epoxy matrix model    O. Tsukamoto and Y. Iwasa Summary: We present the epoxy-crack-induced temperature data of copper wires imbedded in wire-epoxy resin composite model at 4.2 K. The experimental results show that the epoxy-crack-induced temperature rise is higher in the copper wires than in the epoxy matrix, indicating that in stress-induced wire-epoxy failure, stress energy stored in the wire-epoxy matrix is preferrentially dissipated in the wire. A plausible mechanism of the nonuniform dissipation is presented.         The training in epoxy-impregnated superconducting coils    H. Fujita, T. Takaghi, E. Bobrov, O. Tsukamoto and Y. Iwasa Summary: We have investigated the training of epoxy-impregnated superconducting coils. It has been observed that the boundary conditions at the coil ends have a crucial effect on shear-stress-induced epoxy cracks in the winding and consequently on the coil training. The results were quatified using acoustic emission data.         Frictional behavior in superconducting coil    T. Nishiura, S. Owaki, K. Katagiri and T. Okada Summary: Experiments were made to obtain information on the role of friction in instability of superconducting coil. We constructed a pin slide type device for friction test which works at cryogenic temperature. The pin slides on the inner most part of the coil wound by Nb-Ti-Zr-Ta conductor. The effect of load and sliding velocity on the friction behavior was examined. The minimum friction energy rate for quenching of the superconducting coils was estimated as a function of friction and magnet operation conditions.         Study of disturbances in superconducting magnets by acoustic emission method    S. Nishijima, H. Iwasaki and T. Okada Summary: Acoustic emission (AE) from superconducting magnets has been analysed in terms of various AE parameters. From the analysis of irreversible and repeatable AE behavior it was confirmed that the flux motion is minor as the AE sources in the magnet. The mechanical disturbances caused by magnet quench were monitored by the use of coincidence method. Effectiveness of AE techniques for the AE location was also confirmed.         Quench energies of potted magnets    L. Dresner Summary: The quench energy of potted magnets has been studied for the following two extreme models of the winding: (1) treating it as an anisotropic three-dimensional continuum and (2) ignoring heat conduction in the epoxy and treating it as a one-dimensional continuum. For each model, we have obtained a formula for the point-source quench energy, complete up to a single undetermined constant, by applying a combination of dimensional and group-theoretic arguments to the heat balance equation. The undetermined constant has been estimated by solving the heat balance equation approximately. Correction factors are given for taking into account the source's being distributed in space and time. The formulas are compared with available experimental data; agreement is fair.         Quenching in coupled adiabatic coils    J. Williams Summary: The prediction of the effects of a quench on stress and temperature is an important aspect of the design of superconducting magnets. Of particular interest, and the exclusive topic of this study, is the prediction of the effects of quenching in coupled adiabatic coils, such as the multi-section windings of a high field NMR spectrometer magnet. The predictive methods used here are based on the measurement of the time of propagation of quench between turns. From this measurement an approximate algorithum for the propagation time is used in a code which solves the linear differential equations for the coil currents and calculates the movement of normal zone boundaries and hence the associated winding resistance.         Stable normal zones in superconducting coils    X. Zheng and S. Han Summary: The present paper studies the problem of stable normal zones in a superconducting coil. It is shown that there are five solutions, namely; T/sub 1/(X), T/sub 2/(X), T/sub 3/(X), T/sub 4/(X), and T/sub 2/(X), of the heat equatuon that describes a locally uncooled superconducting wire within certain ranges of currents and magnetic fields. Of the five solutions T/sub 1/(X), T/sub 3/(X), and T/sub 2/(X) are stable, and T/sub 2/(X) and T/sub 4/(X) are unstable. Stable stationary solution T/sub 3/(X) describes the short normal zones mainly located in the nucleate boiling range of the coolant. T/sub 1/(X) is the superconducting state, and T/sub 2/(X) having a longer region above the critical temperature than T/sub 3/(X) generally is the quench state. Unstable stationary solution T/sub 4/(X) describes the minimum propagating zones. Normal zones will develop if the temperature profile in the conductor is above T/sub 4/(X); it will contract if the temperature profile is below T/sub 2/(X). Stable normal zones in superconducting cooled by HeII are also discussed. It is easier to get conditions under which stable normal zones exist in HeII than in HeI. Using the theoretical model, a detailed numerical analysis is made that determines a range within which stable normal zones occur. Some experimental results are presented and compared with theoretical calculations.         Some improvements of induced current technique used to measure superconductor short sample critical currents    Wang Enyao, Wang Kuiwu, Zheng Zhigin, Liu Jiamin, Qian Jiakuang, Li Hangi and Wang Qian Summary: Three kinds of typical induced current generators are described. The electronic integrator is replaced by an InSb Hall probe to measure sample currents. The Hall probe is also used to measure the joint resistance of superconductor down to 10/sup 13//spl Omega/ by a decay method.         A subcable test facility    S. Kim Summary: A subcable test facility was prepared to study ac losses and stabiilty of subsize cables under the pulsing magnetic field of a 40-kJ split-pair coil. A G-10 cryostat fabricated for the system has an inner diameter of 31 cm and is 170 cm deep. An 80-kW power supply for the coil has a pulsing mode of triangular operation. Another 500-kW power supply, rated for dc operation at 400 V and 1250 A, can have pulsing modes of triangular, trapezoidal, or (B + /spl dot/B) superimposed. AC losses of a superconducting composite strand with CuNi outer sheath were measured. Coupling losses among the strands were not significant because of the outer sheath.         AC losses in untwisted "in situ" superconductors above the percolation threshold    V. Pan, S. Mukhin, V. Flis, M. Vasilenko, V. Latysheva, L. Fisher and V. Dzugutov Summary: Magnetization measurements in the low frequency ac magnetic field for untwisted in situ prepared superconducting Cu-Nb composites are presented. Wires with various degrees of drawing deformation were examined. Penetration depth in the low field region increases with the deformation of the sample. Behavior of the magnetization curves is analyzed on the basis of a simple critical state model allowing for the suppression of screening currents in high magnetic fields. Agreement of the model with the experimental data is discussed.         Superconducting techniques for gravity survey and inertial navigation    H. Chan, H. Paik, M. Moody and J. Parke Summary: Major improvements in sensitivity and drift can be made in inertial instruments by utilizing benign properties of materials available at liquid helium temperatures. We are developing a three-axis gravity gradiometer in which magnetic fields produced by persistent currents are modulated by motions of superconducting proof masses. Signals arising from both differential and common mode motions of the proof masses are detected by SQUIDs. The present design parameters give an intrinsic gravity gradient noise of 2x10/sup -12/s/sup -2/Hz/sup -1/2/, subject to improvements with new superconducting techniques under tests. A demonstration of such high sensitivity requires a very strict control of all error sources. The performance of our prototype gravity gradiometer when tested in a noisy terrestrial environment with its sensitive axis tilted at an angle of tan/sup -1/ 2/sup 1/2/ with respect to Earth's gravity is degraded to an error level of 7x10/sup -10/s/sup -2/Hz/sup -1/2/. In order to compensate for common-acceleration induced errors, we are also developing a six-axis superconducting, accelerometer, based on a similar principle, which can detect the linear and angular acceleration vectors of the gradiometer platform simultaneously. Motion of a single, magnetically levitated, proof mass is monitored to resolve linear acceleration components to 4x10/sup -12/m s/sup -2/Hz/sup -1/2/and angular acceleration components to 3x10/sup -11/rad s/sup -2/Hz/sup -1/2/. This accelerometer, combined with the gradiometer, represents a gradiometer-aided inertial navigation/survey system.         A superconducting gravitational radiation antenna    P. Veitch, D. Blair, M. Buckingham, C. Edwards and F. van Kann Summary: In this paper we describe the superconducting gravitational radiation antenna being developed at the University of Western Australia (UWA) with particular reference to its high Q properties and the low loss mechanical filter used to support it. Recent measurements of the acoustic quality factor, Q, of the fundamental longitudinal mode of the bar are reported. It is shown that the Q is sufficiently high that it will not contribute significant noise to the antenna until the transducer becomes 'quantum limited'. We also report measurements on a smaller sample down to 0.4 K in which we observe that Q/sup -1/the acoustic loss, decreases exponentially with T/sup -1/between 2 K and 0.4 K.         The NBS magnetic monopole detector    M. Cromar, A. Clark and F. Fickett Summary: We have built and operated several inductive type monopole detectors, the present one having three concentric, orthogonal loops operated in coincidence. The area of each loop is 200 cm/sup 2/and the cross sectional area of the superconducting shield is 700 cm/sup 2/. The detector loops are in a trapped magnetic field of approximately 3 milligauss. The system is mechanically stable and is relatively insensitive to external disturbances, both mechanical and electro-magnetic. The detector is quiet, having a signal-to-noise ratio for monopole detection of approximately 20. We have also investigated several sources of noise and spurious signals which might mimic a monopole event.         Use of a RF-SQUID in a quantum non demolition scheme    F. Bordoni, P. Carelli, V. Foglietti and F. Fuligni Summary: The sensitivity required for detecting gravitational waves seems higher than the limit imposed to a linear detector by quantum mechanics. To overcome this drawback, many groups are developing quantum non demolition (QND) schemes. Here we present a QND scheme based on the use of an RF-SQUID. The SQUID is used as a non linear element in order to obtain a combination of a three frequencies inverting and non inverting up-converter.         Problems in coupling a dc-SQUID to the external world    P. Carelli and V. Foglietti Summary: We constructed two identical planar dc-SQUIDs coupled to different input coils on a single silicon chip. The inductances of the coils differ by two orders of magnitude. The ultimate noise performances do not depend significantly on the input circuit if, as in our case, the coupling constant is of the order of 0.5. In a flux locked loop operating mode the energy sensitivity of the more tightly coupled device is sligtly higher than for the less tightly coupled one. We coupled the device to a second-order gradiometer used for biomagnetic measurements obtaining our best performances to date in such a configuration.         Well coupled, low noise, dc SQUIDs    B. Muhlfelder, J. Beall, M. Cromar, R. Ono and W. Johnson Summary: We have designed, fabricated, and tested a Double Transformer (DT) coupled dc SQUID (Superconducting Quantum Interference Device) with low noise, an input inductance of 1/spl mu/H and a smooth input-output characteristic. A transmission line model is presented to explain a resonance in the input-output characteristic of early versions of this device. Guided by the results of numerical simulations a new version of this device has been built and tested. Experimental results are presented that show that the resonance can be moved to a higher voltage by reducing the area of the SQUID loop. The voltage-external flux characteristic of some of these new devices agrees to within 10% with computer simulations. The minimum detectable energy per unit bandwidth (MDE) referred to the SQUID loop, is 10h, where h is Planck's constant. Computer simulations indicate an MDE of 6h.         Hysteretic noise in dc SQUIDs    D. Drung and W. Jutzi Summary: The energy resolution per bandwidth /spl epsiv/ has been calculated on a hybrid computer for large asymmetry factors a and for large McCumber damping parameters /spl epsiv/. An increase of a from 1 to 4 decreases the energy resolution /spl epsiv/ to 65%. For large damping parameters /spl epsiv/ the low frequency voltage noise S/sub UO/increases approximately exponentially with /spl epsiv/ depending strongly on the bias current I/sub G/. A proper choice of the bias current yields a small /spl epsiv/ even for a large damping parameter /spl beta/ = 6.         Thermal sensitivity of an rf SQUID    J. Claassen, S. Wolf and D. Gubser Summary: A well known limitation to the resolution of pratical SQUID systems is set by the sensitivity of the SQUID output to temperature fluctuations. This is particulary serious in non-stationary systems where agitation of the helium bath inevitable results in temperature fluctuations of the SQUID. We have undertaken to characterize the thermal response of commercial rf SQUIDS and tried to understand the causes of this sensitivity.         Present status of MRI magnets at Oxford    P. Sanger Summary: The advent of magnetic resonance imaging for medical diagnoses has produced the first commercial requirement for large bore superconducting magnets of high-field uniformity and reliability. Oxford Superconducting Technology and Oxford Magnet Technology have succeeded in producing magnets in large quantities, meeting these requirements. As of March 1984, over 200 magnets for MRI have been produced; 150 from 0.3-0.6T and 50 between 1.0-2.0T. For the medium-field range of magnets, field uniformities of 25ppm over a 0.5m diameter sphere and 5ppm over a 0.3m diameter sphere have been consistantly demonstrated. For the high-field range, uniformities of better than 50ppm and 10ppm for the above volumes and 0.1ppm on a 0.1m diameter sphere have been demonstrated. Field stability of better than 0.1ppm per hour is consistantly obtained. The cryogen consumption of the cryostat is less than 0.5 helium liters and 1.0 nitrogen liters per hour. The purpose of this paper is to familiarize the community with the status of this growing application.         The energizing of a NMR superconducting coil by a superconducting rectifier    J. Sikkenga, J. Knoben, C. Spoorenberg, G. Kraaij, L.J.M. Klundert and H. ten Kate Summary: NMR magnets require a good homogeneity within a certain volume and an excellent field stability. The homogeneity can be met using a superconducting shim coil system. The field stability requires a constant current, although in many cases the current decay time constant is too low, due to imperfections in the superconducting wire and joints. This can be overcome using a rectifier. The rectifier can also be used to load the coil. The combination and interaction of the superconducting NMR coil (2.0 Tesla and 0.35 m cold bore) and the rectifier (20 W / 1 kA) is tested. The safety of the system is discussed. The shim coil system can compensate the strayfield of the rectifier. The field decay compensation will be discussed.         Superconducting electromagnets for large wind tunnel magnetic suspension and balance systems    R. Boom, Y. Eyssa, G. McIntosh, M. Abdelsalam, R. Scurlock, Y. Wu, M. Goodyer, K. Balcerek, J. Eskins and C. Britcher Summary: This paper presents a new design study of a Magnetic Suspension and Balance System (MSBS) for airplane models in a large 8 ft X 8 ft wind tunnel. New developments in the design include: use of a superconducting solenoid as a model core instead of magnetized iron; combination of permanent magnet material in the model wings along with four racetrack coils to produce the required roll torque; and mounting of all the magnets in an integral cold structure instead of in separate cryostats. Design of superconducting solenoid model cores and practical experience with a small-scale prototype are discussed.         Field enhancement of a 12.5-T magnet using holmium poles    R. Hoard, S. Mance, R. Leber, E. Dalder, M. Chaplin, K. Blair, D. Nelson and D. Van Dyke Summary: Unlike conventional ferromagnetic materials such as iron and Supermendur, which produce saturation magnetization fields of approximately 2 T, several of the rare-earth elements (holmium, terbium, erbium, gadolinium, and dysprosium) yield saturated fields of nearly 4 T. This property makes these rare-earth metals particularly attractive as flux concentrators for use in superconducting magnets. This report concerns the use of holmium inserts to enhance the peak useful field of the nominally 12.5-T, 5-cm-bore tape magnet manufactured by the Intermagnetics General Corporation (IGC). Nonlinear magnetostatic analysis indicates that this field increases to nearly 16 T with the rare-earth poles inserted within the bore on both sides of the coil's split-plane radial access gap. This paper focuses on computer modeling methods and experimental results.         Superconducting electromagnetic actuators for astronomical Fabry-Perot interferometers    T. Nishimura, F. Low and K. Shivanandan Summary: Two types of superconducting electromagnetic actuators-linear and angular-for precise control of Fabry-Perot spectrometer etalons at liquid helium temperature were manufactured and tested successfully. The linear displacement unit (45 Newtons/Amp) has maximum travel of /spl plusmn/44 um with off-axis deviation of less than 1.5 arcseconds for 15 um path. The angular unit has maximum tilt of /spl plusmn/ 8 arcminutes and can maintain parallelism of Two etalons to better than 0.3 arcsecond of angle by compensating the differential contraction upon coaling and off-axis deviation of the linear displacement unit. These actuators are proving especially useful in low temperature infrared instrumentation where other choices, such as piezoelectric crystals, fail and where essentially zero power dissipation permits low infrared backgrounds to be maintained along with long cryogenic lifetimes.         Microstructure and internal strain control in NbN on carbon fibers    M. Dietrich Summary: Magnetron sputtering technique has been used for the NbN formation on moving carbon fiber bundles. For an NbN film thickness of about 0.5 /spl mu/m, the mean crystallite size could be controlled from 25 nm to 10 nm by an applied bias. Without bias, the NbN coatings reveal tensile strains due to the lower thermal expansion of the carbon fibers used. This strain can be reversed to a compressive strain as function of bias. The superconducting T/sub c/values are about 16 K, the critical current density values are about 10/sup 5/A/cm/sup 2/at 4.2 K and 13 tesla. B/sub c2/values were extrapolated to 35 tesla. Some conclusions for this alternative conductor concept are given.         Application of NbN films to the development of very high field superconducting magnets    R. Kampwirth, D. Capone II, K. Gray and A. Vicens Summary: We report the preliminary results of a program recently begun at Argonne National Laboratory to demonstrate the feasibility of using niobium nitride (NbN) films as practical high field superconductors. Films of varying thicknesses (2-9 /spl mu/m) have been deposited on sapphire and Hastelloy substrates, using d.c. magnetron sputtering. The superconducting transition temperatures T/sub c/of these films range from 12-15 K. Using the WHH extrapolation, upper critical fields H/sub c2/(O) up to 36 T in the parallel direction and 43T in the perpendicular direction were obtained. Critical current densities J/sub c/(H,4.2 K) were /spl ap/1 /spl times/ 10/sup 4/ A/cm/sup 2/at 20 T in both the parallel and perpendicular directions. The preliminary results from novel sample preparation technique for TEM studies of film cross-sections is briefly described. This technique shows the variation in film structure as a function of distance from the substrate.         Fabrication of superconducting composite tapes by a newly developed liquid quenching technique    K. Togano, H. Kumakura, Y. Yoshida and K. Tachikawa Summary: A new liquid quenching technique for preparing composite tapes composed of superconducting compound and copper substrate has been developed. In this technique, the alloy melted by r.f. levitation-melting is ejected through a nozzle as a molten alloy jet onto a high-speed moving copper tape heated at a proper temperature. The heating of the substrate improves quenching effect and the resulting composite has good bonding between the alloy layer and the copper substrate, which may enable the use of copper as a stabilizing material. Using this technique, composite tapes of V/sub 40/(Hf.Zr)60 amorphous alloy layer and copper substrate were successfully prepared at tape speeds of 10-20m/sec. The amorphous layer was then transformed by annealing into a veryfine crystalline mixture of /spl alpha/ + Laves phases, having a critical current density J/sub c/of 5 /spl times/ 10/sup 4/A/cm/sup 2/at 10 T and 4.2 K. Preliminary experiment for applying this technique to Nh/sub 3/(Al.Ge) has been also carried out. The composite tape of bcc-Nb/sub 3/(Al.Ge) and copper substrate was successfully formed, and the bcc-Nb/sub 3/(Al.Ge) was then transformed into Al5 structure having a J/sub c/exceeding 10/sup 5/A/cm/sup 2/at 16 T and 4.2 K.         Temperature dependences of superconducting critical current density and upper critical field for V/sub 2/(Hf, Zr) multifilamentary wire    K. Inoue, T. Kuroda and K. Tachikawa Summary: The temperature dependences of the critical current density, J/sub c/, and the upper critical field, u/sub o/H/sub c2/, have been studied for newly developed V/sub 2/(Hf,Zr) multifilamentary wires. At 4.2 K, a /spl mu//sub o/H/sub c2/of 22 T and an over-all J/sub c/of 1/spl times/10/sup 4/A/cm/sup 2/at 17 T are obtained for these wires. At 1.8 K, overall J/sub c/in 15 T of these wires are twice as large as that of the bronze-processed Nb/sub 3/Sn multifilamentary wire. The enhanced J/sub c/at reduced temperatures may be attributed to the rapid increase in /spl mu//sub o/H/sub c2/by using the temperature scaling law of the pinning force density, /spl mu//sub o/H/sub c2/measured in pulsed fields is about 28 T at 2.0 K. According to the temperature scaling law, the overall J/sub c/for 1.8 K and at 20 T is estimated to be 2/spl times/10/sup 4/A/cm/sup 2/. Thus, the present V/sub 2/(Hf,Zr) multifilamentary wires are very promising for use of generating high magnetic fields in the superfluid liquid helium environment.         Critical currents of superconducting PbMo/sub 6/S/sub 3/tapes    K. Hamasaki, K. Hirata, T. Yamashita, T. Komata, K. Noto and K. Watanabe Summary: An electro-plating and diffusion method has been developed for the production of superconducting ternary lead molybdenum sulfide (PbMo/sub 6/S/sub 8/) tapes. These tapes were prepared by plating a Mo tape with lead, and with subsequent heat treatment in sulfur (S) vapour from molybdenum sulfide (MoS/sub 2/). Samples were examined with SEM, XMA, and X-ray diffraction Optimal reaction-temperature and Pb-plating conditions gave a critical temperature of about 14 K, and a resistive transition width of less than 1 K. The value of J/sub c/was relatively large, and reached 1.8/spl times/10/sup 4/A/cm/sup 2/in a 14 T magnetic field at 4.2 K. The relatively large values of J/sub c/in strong magnetic field suggest the need for a more detailed analysis of the preparation conditions and the pinning mechanism in this compound.         Effect of uniaxial strain on the critical current and critical field of Chevrel phase PbMo/sub 6/S/sub 8/superconductors    J. Ekin, T. Yamashita and K. Hamasaki Summary: The first measurements of the effect of uniaxial strain on the critical current of a Chevrel phase superconductor, PbMo/sub 6/S/sub 8/, have been obtained at 4.2 K in magnetic fields from 2 T to 24 T. The data show there is a very significant reversible effect of elastic strain on the critical current of PbMo/sub 6/S/sub 8/, comparable in magnitude to that observed in Nb/sub 3/Sn. This is because both the peak pinning force and upper critical field are very sensitive to elastic strain. A correlation is noted between the elastic strain effect, radiation sensitivity, and crystal phase.         Model magnet studies    A. McInturff, J. Carson, N. Engler, H. Fisk, R. Hanft, R. Lundy, P. Mantsch, T. Nicol, R. Niemann, E. Schmidt and A. Szymulanski Summary: A design, construction, and testing program for model magnets is underway at Fermilab to evaluate alternatives in the development of small aperture magnets. The most thoroughly developed of these programs utilizes a set of model magnets based on the Tevatron quadrupoles and dipoles as a standard. These 7.6cm aperture model magnets, approximately 64cm long, have construction or material changes which are to improve quality and/or cost effectiveness. There are also superconductor parameter changes, as well as construction and materiai parameters, which impact or give insight into the choices of material specifications and construction parameters for the 5cm aperture model magnet series which are prototype candidates for the Superconducting Super Collider (SSC) ring magnets. The test program consists of performance test quenching of the windings at various temperatures until the cable critical current is reached. The quality of the magnetic field (Fourier coefficients) B(n) and quenching current is measured versus ramp rate, dB/dt, intensity, B, magnet temperature, and conductor parameters. The magnetization of the windings is measured as a function of these same parameters. There are also other special measurements made, i.e., deflection of coils. Two 5cm diameter aperture SSC candidate dipoles without iron are being prototyped: (a) a two layer, 6kA/turn version and (b) a single layer 10kA/turn model. In addition, there is a collaborative effort between KEK and FNAL in the development of a 10T (dipole, a longer range model) magnet program.         Development of high field Nb-Ti accelerator dipoles    W. Hassenzahl, W. Gilbert and C. Peters Summary: A four layer, 5 cm beam tube aperture, 1-m, long model accelerator dipole has been built and recently tested at the Lawrence Berkeley Laboratory. The conductor for this dipole is graded. The cable used for the inner two layers has about 30 percent more superconductor than that in the outer two layers, so the conductors reach the short sample limit at nearly the same current. This magnet is the third of a series of high field dipoles under development at LBL and has been tested at 1.8 and 4.2 K in liquid helium at one atmosphere pressure. Because of the large forces exerted at high field the magnitude and distribution of prestress in the assembled coil is quite important. The stress in each layer was measured and adjusted quite closely during the assembly process. The magnet achieved 9.08 T at 1.8 K and 7.15 T at 4.4 K. These fields appear to correspond to the critical current limits of the conductors in the region of the splice between layers 3 and 4. Training behavior, ramp rate sensitivity and magnetic field measurements are described.         Superconducting sextupole correction coil operating in persistent mode    W. Gilbert, A. Borden, W. Hassenzahl, G. Moritz and C. Taylor Summary: Error fields in a dipole due to superconductor magnetization and conductor misplacements add unwanted multipole, mainly sextupole and decapole, terms to the desired dipole field. Two persistent mode sextupole correction coils inside the bore of model SSC dipoles have been built and tested. A shorted superconducting sextupole coil has a current induced in it by the error sextupole field such that no sextupole field can penetrate into the proton beam region. The correction sextupole coils are one layer thick and are wound from a single length of insulated composite Nb-Ti and copper wire 0.60 mm in diameter. Each of the six poles has ten turns and is mounted on a 1.75 cm radius stainless steel bore tube. Details of testing and trimming of the correction coils are described. Test results of the measured magnetic field within the model SSC dipoles with the correction coils in and out of persistent mode operation are presented. An electrical heater is used to drive the coil out of the persistent mode. Measurements of joint resistance and coil decay time constants are also given.         Design of a 5.5 metre diameter superconducting solenoid for the Delphi particle physics experiment at LEP    R. Apsey, D. Baynham, P. Clee, D. Cragg, N. Cunliffe, R. Hopes and R. Stovold Summary: A magnet comprised of a superconducting solenoid surrounded by an iron yoke is required to produce 1.2 Tesla in a room temperature volume of 5.2 metres diameter by 6.8 metres long. A single layer main coil is wound with pure aluminium clad Nb-Ti conductor on the inside of a support cylinder. Series connected field correction coils are located at each end of the main coil. The operational current is 5kA. The coil is indirectly cooled with pumped two-phase 4.5K He and is suspended within an 80K gas cooled radiation shield inside a stainless steel vessel. The paper covers the design concept, field and force computations, coil winding and bonding R&D, plus the fabrication proposals.         A large superconducting thin solenoid magnet for TRISTAN experiment(VENUS) at KEK    M. Wake, T. Matsui, K. Ishibashi, T. Satow, O. Asai, K. Kuno, T. Kawaguchi, K. Wakamoto, R. Fujita and H. Hirabayashi Summary: A 30 Gev e+e- collider TRISTAN is now under construction at KEK. The detector system VENUS in TRISTAN requires a large space of 7.5 kG magnetic field for the tracking of the particles while keeping the material thickness of the magnet as thin as possible. The superconducting thin solenoid magnet which is in the middle of the construction has 3.4m in warm bore diameter and 5.24m in usable length with material thickness of 0.52 radiation length. The geometrical thickness of the magnet is as thin as 208 mm while the outside dimension is as large as 4m /spl phi/ spl times/ 5.64m. Since the electro-magnetic force is toward outside, the coil is supported by an aluminum 'case' covering outside the coil instead of a bobbin in the coil. The water cooled welding technique and an expandable mandrel were developed to form the coil-case composite. The conductor is made of NbTi/Cu and pure aluminum stabilizer is extruded so as to contain the conductor in the stabilizer. The cooling of the magnet is provided by the forced flow of two phase helium in the cooling channel of the 'case'. The cryostat uses CFRP (Carbon Fiber Reinforced Plastics) to reduce the material thickness of the magnet. The construction method and the design were confirmed by 1m/sup ph/ superconductive model and real size non-superconductive model. Major components such as conductors and cryostat have been completed and the magnet will be excited next spring.         NbN tunnel junctions    J. Villegier, L. Vieux-Rochaz, M. Goniche, P. Renard and M. Vabre Summary: All-Niobium Nitride Josephson junctions have been prepared successfully using a new processing called SNOP : Selective Niobium (Nitride) Overlap Process. Such a process involves the "trilayer" deposition on the whole wafer before selective patterning of the electrodes by optically controlled Dry Reactive Ion Etching. Only two photomask levels are need to define an "overlap" or a "cross-type" junction with a good accuracy. The properties of the Niobium Nitride films deposited by DC-Magnetron sputtering and the surface oxide growth are analysed. The most critical point to obtain high quality and high gap value junctions resides in the early stage of the NbN counterelectrode growth. Some possibilities to overcome such a handicap exist even if the fabrication needs substrate temperatures below 250/spl deg/C.         Niobium nitride thin films for use in Josephson junctions    E. Cukauskas, W. Carter, S. Qadri and E. Skelton Summary: The properties of rf diode and magnetron reactively sputtered NbN films have been studied under a variety of preparation conditions. The aim of this investigation is to achieve high transition temperature, low resistivity films under conditions suitable for use in all refractory tunnel junction fabrication. We have systematically varied the relative amounts of Ar, N/sub 2/and CH/sub 4/gases, and the substrate temperature used during film growth. The transition temperature, resistivity, lattice parameter and crystal structure have been studied and correlated with the partial pressure of methane used during sputtering. The crystal structure was investigated using diffractometer and Read camera photographic X-ray techniques. We have prepared NbN films using both rf diode and magnetron sputtering with resistivities less than 70 /spl mu//spl Omega/-cm and transition temperatures greater than 16 K. The lattice parameter for our NbN films ranges between 4.39 /spl Aring/ and 4.45 /spl Aring/ and is dependent upon the amount of nitrogen and carbon used in the film preparation. We are currently investigating all refractory tunnel junctions with artificial barriers using these films as base electrodes and niobium counter electrodes.         Tunneling, resistive and structural study of NbN and other superconducting nitrides    M. Gurvitch, J. Remeika, J. Rowell, J. Geerk and W. Lowe Summary: A straightforward method for producing metal nitrides, which we call Thin Film Diffusion (TFD), has been developed. With this technique we produced films of cubic nitrides (NbN, ZrN, VN, TiN) with superconducting transition temperatures up to 17.25K in NbN (equal to the highest known in this material), and up to 9.4K in VN (0.6K higher than the highest previously reported value). Resistive transitions are less than 0.1K in width, indicating, together with x-rays, that the samples are homogeneous and essentially single BI phase. In NbN the relatively low resistivity /spl rho/(20K) = 65 /spl mu//spl Omega/cm and metallic resistance ratio /spl rho/(300K)//spl rho/(20K) - 1.2 were found. TFD films open up new possibilities in tunneling and other experiments on cubic nitrides. Our present results include determination of the strong coupling parameter 2/spl utri/(0)kT/sub c/= 4.31 and of the electron-phonon coupling function /spl alpha//sup 2/ F(/spl omega/) in NbN./spl alpha//sup 2/ F(/spl omega/) is found to have a peak at /spl sim/13 meV, which explains the strong-coupling nature of NbN. In resistive studies we found an interesting similarity between the low temperature resistivity behavior of cubic nitrides and A-15 superconductors.         Behavior of T/sub c/of high temperature superconducting films and a determination of their parameters    V. Kresin Summary: Existence of the proximity layer in Nb and NbN films leads to a peculiar dependence of the critical temperature upon the film thickness. Expressions describing T/sub c/for S/sub /spl alpha//-S/sub /spl beta// and S/sub/ /spl alpha//-N/sub /spl beta// proximity systems are obtained. The theory allows to explain the dependence T/sub c/(L) which has been observed experimentally. Measurements of T/sub c/can be used in order to determine the electronic density of states in the surface layer.         Reactively sputtered V/sub 3/Si and Nb/sub 3/Ge films    J. Gavaler and J. Greggi Summary: We have investigated the reactive sputtering of V-Si and Nb-Ge films in a dc diode and in a magnetron sputtering system toward the possible use of such films in high (/spl sim/ 10K) operating temperature Josephson devices. Large differences in the dependence of T/sub c/on deposition temperature and on average film composition were found. Above 700/spl deg/C maximum T/sub c/'s of 16.8K in V/sub 3/Si and 21K in Nb/sub 3/Ge were obtained in the dc diode sputtered films. Below this temperature T/sub c/'s degraded, however at 500/spl deg/C values of close to 12K were still found in both sets of films. Transmission electron microscopy studies indicate that a growth mechanism operates during both sputtering processes which can produce adjacent grains which have greatly different compositions. As a result, high T/sub c/'s in both Nb-Ge and V-Si can be obtained in films which have average compositions very far removed from ideal 3/1 stoichiometry.         Tunneling and interface structure of oxidized metal barriers on A15 superconductors    J. Talvacchio, A. Braginski, M. Janocko and S. Bending Summary: Al5-based tunnel junctions have been prepared with barriers of oxidized Al; Si, and Y. Properties of the superconductor/barrier interface which are crucial for low-leakage junctions were established by correlating XPS spectra of oxidized bilayers and RHEED patterns of the surface of each layer with tunneling characteristics. Comparisons were made between oxidized Al barrier properties for Nb and Nb/sub 3/Sn base electrodes. Some differences between evaporated and dc magnetron sputtered barriers have emerged.         RF surface resistance in Nb/sub 3/Sn thin films    L. Allen, W. Anklam, M. Beasley, R. Hammond and J. Turneaure Summary: We have prepared thin films of Nb/sub 3/Sn by electron-beam co-evaporation and measured their surface resistance between 1.5 and 18K. As previously reported, broad transitions and excessive losses were found, indicating the presence of inhomogeneities in our materials. We describe a new deposition procedure, phase-locking, which results in more homogeneous materials. Samples made with this technique have sharper transitions and very good agreement with BCS predictions, once the residual losses (/spl sim/ .01m /spl Omega/) are removed.         Nb and Nb-based A15 compound tunnel junctions fabricated using a new CF/sub 4/cleaning process    O. Michikami, K. Tanabe, Y. Kato and H. Takenaka Summary: A new surface cleaning technique, the CF/sub 4/Cleaning Process (CFCP), is proposed for the fabrication of Nb and Nb-based Al5 compound tunnel junctions with native oxide barriers. The effects of fabrication conditions and these superconducting material properties on the characteristics of these junctions with Pb or Pb alloy counterelectrodes are investigated. High-quality junctions with a well-defined gap, no knee and very low excess conductance are successfully fabricated through the conventional lift-off technique for Al5 compounds (Nb/sub 3/Al, Nb/sub 3/Ge and Nb/sub 3/Si) as well as Nb. Arrays of 100 series-connected 2 /spl mu/m/spl phi/ Nb/Pb-Bi Junctions are fabricated with the standard deviation (/spl sigma/) of critical current (J/sub c/= 15.1 KA/cm/sup 2/) equal to 2.5 %. The CFCP mechanism that contributes to the formation of such good junctions is studied using in-situ X-ray photoelectron spectroscopy (XPS). Chemical shifts of the Nb 3d levels on the CF/sub 4/plasma-cleaned Nb surfaces indicate the presence of an Nb-F layer. These XPS spectra show that the tunnel barrier is composed of mixed Nb/sub 2/O/sub 2/and Nb-FO compounds.         High-T/sub c/superconducting integrated circuit: A dc SQUID with input coil    M. Di Iorio and M. Beasley Summary: We have fabricated a high transition temperature superconducting integrated circuit consisting of a dc SQUID and an input coupling coil. The purpose is to ascertain the generic problems associated with constructing a high-T/sub c/circuit as well as to fabricate a high performance dc SQUID. The superconductor used for both the SQUID and the input coil is Nb/sub 3/Sn which must be deposited at 800/spl deg/C. Importantly, the insulator separating SQUID and input coil maintains its integrity at this elevated temperature. A hole in the insulator permits contact to the innermost winding of the coil. This contact has been achieved without significant degradation of the superconductivity. Consequently, the device operates over a wide temperature range, from below 4.2 K to near T/sub c/.         Study of preparation techniques for a practical microbridge dc-SQUID structure fabricated from Nb/sub 3/Ge    H. Rogalla, B. David, M. Muck and Y. Kato Summary: Tests with a small area Nb/sub 3/Ge dc-SQUID structure revealed promising results: a wide operating temperature range extending up to 20.2 K was achieved with a best modulation depth of 15%. Here we describe development steps towards a more practical device: enlargement of the flux sensitive area and integration of a Nb/sub 3/Ge coupling coil For this purpose a Nb/sub 3/Ge multilayer technique was developed using SiO/sub 2/insulating layers. To optimize the behavior of the very small microbridges the influence of reactive ion etching parameters on the decrease of T/sub c/during the preparation was studied.         High quality all refractory Josephson tunnel junctions for SQUID applications    J. Lumley, R. Somekh, J. Evetts and J. James Summary: We report on Nb based all-refractory Josephson tunnel junctions made using a combination of UHV getter sputter deposition, CF/sub 4/plasma etching and ion beam etching/deposition. Like the SNEP process developed by Gurvitch et al. the junction forming steps are performed without breaking vacuum, producing a whole wafer Nb-Al-AlO/sub x/-Al-Nb sandwich. Two routes have been used to produce 20/spl mu/m X 20/spl mu/m junctions from the sandwich structure, one of which includes a novel liftoff stage. The Nb layers are deposited at 700/spl deg/C for the base electrode and 100-400/spl deg/C for the top electrode. The Al layers are deposited and oxidised at 80-180/spl deg/C. Both randomly oriented and 'R'-plane single crystal sapphire substrates are used, the latter enabling epitaxial single crystal Nb to be grown. We have made a preliminary study to characterise the junctions with respect to the temperature of oxidation and of the top electrode deposition.         Sputter fabricated Nb-oxide-Nb Josephson junctions incorporating post-oxidation noble metal layers    R. Bain and G. Donaldson Summary: We present an extension, involving other metals, of the work of Hawkins and Clarke, who found that a thin layer of copper prevented the formation of the superconductive shorts which are an inevitable consequence of sputtering niobium counter-electrodes directly on top of niobium oxide. We find gold to be the most satisfactory, and that 0.3 nm is sufficient to guarantee short-free junctions of excellent electrical and mechanical stability, though high excess conductance means they are best suited to shunted-junction applications, as in SQUIDs. We present results for critical current dependence on oxide thickness and on gold thickness. Our data shows that thermal oxide growth is described by the Cabrera-Mott mechanism. We show that the protective effect of the gold layer can be understood in terms of the electro-chemistry of the Nb-oxide-Au structure, and that the reduced quasi-particle resistance of the junctions relative to gold-free junctions with evaporated counterelectrodes can be explained in terms of barrier shape modification, and not by proximity effect mechanisms. The performance of a DC SQUID based on these junctions is described.         A novel technique for tunnel junction diagnostics    G. Hertel and T. Orlando Summary: We present a way to diagnose problems in the preparation of tunnel junctions by numerical deconvolution of the differential conductance data. The conductance of a junction can deviate from the ideal BCS conductance by a broadening in the gap region. The broadening can be due to several causes: The smearing can be caused by the presence of two distinct phases with two different energy gaps or by a continuous distribution of energy gaps, due to either anisotropy effects or proximity effect from a contaminated surface. These cases may not be distinguishable in a measurement at finite temperature. But after the thermal smearing is removed by numerical deconvolution, the details in the distribution of energy gaps can be restored. This has important applications for the study of junctions on transition metals and especially on high T/sub c/ternary superconductors like Chevrel phases and rhodium borides, where these methods may reveal features in the density of states, which are not apparent in the conductance data because of thermal smearing. The performance and potential of numerical deconvolution methods are discussed and demonstrated on tunneling data of a V/sub 3/Ga-junction in a magnetic field.         Determination of the penetration depth of type II superconducting films    J. Moodera, R. Meservey and P. Tedrow Summary: The superconducting penetration depth /spl lambda/(0) at T = 0 was determined for NbN films from the temperature dependence of the frequency of a tunnel-diode-driven resonant circuit whose inductive element was a thin film meander line of superconducting NbN. The BCS temperature dependence of the penetration depth /spl lambda/(t) was assumed. Measurements were made on two stoichometric NbN films 310 nm and 465 nm thick and a nitrogen-deficient film 55 nm thick. The values of /spl lambda/(0) obtained were 276, 280, and 175 nm respectively. These values are compared with other determinations of /spl lambda/(0). This method provides a simple method of obtaining /spl lambda/(0) for thin films where other techniques may not be practical.         A Josephson four-bit full adder using direct coupled functional gates    G. Matheron, Ph. Migny and O. Sie Summary: A Josephson 4-bit full adder circuit using functional direct coupled gates has been designed and studied through computer simulations. The circuit consists of only 27 gates taken from a complete logic family composed of OR, AND, EXOR and MAJORITY gates. The proposed adder scheme needs 180 Josephson junctions and 150 thin film resistors. The computed critical path delay was found 180 ps/4bits for carry propagation, with a power dissipation estimated to be less than 100 /spl mu/W on the basis of a Nb/Pb-In technology with 4 /spl mu/m minimum linewidth and with a Josephson current density of 1000 A/cm/sup 2/. The worst case total add time for the 4 bits has been found less than 300 ps.         A novel current injection Josephson logic cell with OR/AND personalization    G. Matheron and Ph. Migny Summary: A novel current injection Josephson logic cell with no need of thin film resistors for proper input output isolation is described. It comprises three parallel connected branches with three junctions each. The control currents are symmetrically applied to the side branches, whereas the feed point position defines the behaviour of the cell as an OR or AND gate. Input-output isolation ratio of about 20 is obtained by using the non-linearity of the I-V curve of the junctions.The static threshold curve of this cell can be optimized through the choice of the critical current of the junctions in each branch. Computer simulations performed on this cell show its high input sensitivity, high gain and high switching dynamics due to reduced turn-on-delay and lowered capacitance.         Optimization of propagation effects in a superconducting sampler    H. Hafdallah, P. Crozat and R. Adde Summary: We investigate propagation effects related to the finite size of circuit elements (superconducting transmission lines and resistive lines) in a superconducting sampler. We give design rules to optimize the main functions of the circuit, electronic ramp, pulser and comparator, in a technology of Nb/Pb edge-grown Josephson junctions and undamped interferometers.         Switching time limits of loaded OR/AND RCJL Josephson logic gates    A. de Lustrac and R. Adde Summary: We have investigated by computer simulation the performances of loaded OR/AND RCJL logic gates with fan in/fan out (2 or 3) and picosecond Josephson Junctions (R/sub n/C /spl ges/ 2 ps). We propose new gate structures designed to have small turn on delay and taking the best advantage of fast Junctions. The shunt on the input Junction responsible of long t.o.d, is eliminated. The static and dynamic operation of the gates are analyzed to operate with moderate overdrive (20%), 25% static margins, low power dissipation in the sub-ten-picosecond range using available technology.         A novel adder by using the unidirectional CIL    M. Morisue, K. Isaji and Y. Kosaki Summary: This paper describes a novel Josephson adder using unidirectional CIL gates. An unidirectionality of a signal is achieved by introducing a decoupling coil to output line of CIL gate. Furthermore a high speed carry propagation technique is introduced. These lessen the total turn-on time for the gate and make the construction of circuit simple. The principle of the operation and design criteria are described in detail. The results of the simulation show that the delay time of the adder is about 33ps/stage and power consumption is 1.7 /spl mu/W/stage.         Dynamic threshold characteristics of Josephson switching gates    M. Morisue, K. Isaji and M. Kaneko Summary: This paper describes the dynamic threshold characteristics of Josephson switching gates. When high speed input signals are applied to the Josephson logic gate, the threshold characteristics of the gate are not always in accord with the well-known static threshold curves. This is because the static threshold curves are affected by quantum flux change in Josephson junctions under the high speed operation. The dynamic threshold characteristics of two typical logic gates, one is the CIL gate and the other the interferometer, are described in detail.         Proposal of unilateral single-flux-quantum logic gate    H. Miyake, N. Fukaya, Y. Okabe and T. Sugano Summary: A new type of single flux quantum logic gate is proposed, which can perform unilateral propagation of signal without using three-phase clock. This gate is designed to be built with bridge-type Josephson junctions. A basic logic gate consists of two one-junction interferometers coupled by superconducting interconnecting lines, and the logical states are represented by zero or one quantized fluxoid in one of one-junction interferometers. The bias current of the unequal magnitude to each of the two one-junction interferometers results in unilateral signal flow. By adjusting design parameters such as the ratio of the critical current of Josephson junctions and the inductances, circuits with the noise immunity of greater than 50% with respect to the bias current have been designed. Three cascaded gates were modeled and simulated on a computer, and the unilateral signal flow was confirmed. The simulation also shows that a switching delay about 2 picoseconds is feasible.         A direct coupled Josephson sampler concept with a vortex to vortex transition sampling pulse generator    H. Kratz and W. Jutzi Summary: A Josephson sampler with direct resistive coupling between sampling gate and sampling pulse generator has been designed and simulated. The sampling gate and the sampling pulse generator comprise two Josephson junction interferometers. A short sampling pulse of 3ps width is generated at a suitable vortex to vortex transition. Delays up to 200ps between the sampling pulse and the main trigger input could be generated with an electronically adjustable circuit on the same chip. A layout of the complete sampling circuit, i.e. the sampling gate, the sampling pulse generator and the electronic delay circuit on a single 36mm/sup 2/chip has been achieved for the Nb-Nb/sub x/O/sub y/-PbInAu technology. The minimum line width is 8/spl mu/m. For j/sub max/ = 3kA/cm/sup 2/a time resolution of 3.5ps is predicted.         Electronic simulation of multi-Josephson-junction circuits    V. Kornev, K. Platov and K. Likharev Summary: A high-speed electronic analog for high-accuracy simulation of complex multi-Josephson-junction circuits has been developed. The analog contains only two types of special cicuits, A and B, interconnected with a simple high-frequency commutation circuit and several ordinary operational low-frequency amplifiers. With our present five-junction version of the analog, several problems of urgent interest have been solved, including those of chaos excitation in the double-junction interferometer and mutual phase locking in multi-tunnel-junction arrays.         Chaotic behavior observed in a dc-biased Josephson junction driven at FIR frequencies    Qing Hu, J. Free, M. Iansiti, O. Liengme and M. Tinkham Summary: We have investigated the response of a Nb-aSi-Nb junction to far-infrared laser radiation at 245, 419, and 604 GHz. At 419 GHz, which is close to the junction plasma frequency, the laser-induced steps in the I-V curves exhibit chaotic behavior over a considerable range of laser driving power. For example, regions of meandering voltage may appear on an otherwise well-defined and flat step. At such chaotic parts of the I-V curves, there is an extremely high level of low-frequency noise, corresponding to a noise temperature of /spl sim/10/sup 11/K at frequencies around 100 Hz. Negative resistance regions are also observed. At some laser power levels, the I-V curve shows the 2/3 Josephson subharmonic step even in the absence of the 1st step. Smooth I-V curves reappear as the laser power is increased, showing the existence of chaos-free windows. The I-V curves taken at 245 GHz also show chaotic behavior, but those taken at 604 GHz are quite smooth. All these features are in good agreement with the results of digital simulations which confirm their chaotic nature.         High frequency spectral analysis of superconducting microstrip lines    H. Abiri-Jahromi, J. Chilo and C. Monllor Summary: A dynamic analysis based on a spectral method is developped for superconducting lines. The propagation characteristics, the current densities distributions and the magnetic field are calculated for a simple or two coupled lines. The thicknesses of the strips are at the origin of an important dimensional effect. The propagation of even and odd modes is examined. For the lines operating at frequencies below several tenths of gigahertz, the results calculated by the spectral method are in good accordance with those obtained by a quasi-static method supposing the TEM approximation verified.         Magnetic study of double layered NbN-Nb microstrip line    J. Chilo, G. Angenieux and C. Monllor Summary: We propose a complex potential method allowing the magnetic characterization of multisupraconductor transmission lines. We apply it to the case of double layered strips. With the use of a moment method (matching point technique), we compute the current density distributions, the inductance and the effective London penetration depth /spl lambda//sub eff/for a NbN-Nb double layered film. The results show an importantt decrease of the inductance when the thickness of the Nb layer is reduced. Experimental and theoretical results are compared.         An absolute SQUID magnetometer    J. Gallop and W. Radcliffe Summary: A prototype free precession magnetometer is described which uses a SQUID to detect the precessing nuclear magnetisation of a sample of/sup 3/He. The expected sensitivity is compared with that of a simple SQUID . Other advantages to be gained from this low noise absolute magnetometer are also discussed.         Superconducting magnetic shielding for SQUID-based systems operating in low fields    T. Clem Summary: A SQUID-based assembly has been designed, built and tested to evaluate the effectiveness of SQUID superconducting magnetic shielding for systems operating in external fields less than 10 gauss. This system is designed to measure changes in magnetic induction interior to test shields due to changes in external field and temperature. Preliminary experimental results are presented in order to study the shielding performance of commercially available superconducting materials and to identify significant parameters for shielding effectiveness. In addition, empirical results are compared with a derived expression describing thermally induced field changes in terms of variations in penetration depth.         A prototype superconducting gravity gradiometer    F. van Kann, C. Edwards, M. Buckingham and R. Penny Summary: We report the successful laboratory test of a single-axis gradiometer designed to measure a diagonal component of the earth's gravitational gradient tensor. It Consists of a pair of accelerometers mounted with their sensitive axes vertical and in line. The difference in displacement of the accelerometers is proportional to the component of the tensor gradient and is sensed via the modulated inductance of a superconducting coil coupled by a superconducting transformer into an RF biased SHE SQUID with energy sensitivity 4x10/sup -29/J/Hz. Rejection of in-line common mode accelerations is achieved by trimming the natural resonant frequency of each accelerometer: the restoring force acting on an accelerometer test mass is partly magnetic and can be trimmed by adjusting the persistent currents in a pair of force coils. A common mode rejection ratio exceeding 95 dB has been achieved in the presence of linear accelerations /spl sim/10/sup -3/ ms/sup -2/, and a laboratory generated gradient of 30 Eo rms has been detected with a signal to noise ratio of about 100. The dependence of this signal on the distance between source and detector has the expected Newtonian form. Under quiet conditions the background noise level of the instrument is at present 3 Eo/ /spl radic/Hz. ( 1 Eo = 10/sup -9/s/sup -2/.) This is close to the practical limit achievable for such a single axis configuration: a three axis instrument for geophysical application is under development.         LC resonances in Nb baselayer dc SQUIDs    G. Paterno, A. Cucolo and G. Modestino Summary: LC resonances in planar interferometers with two Nb-NbOx-Pb Josephson junctions have been investigated. The junction areas are defined by two "windows" in an SiO insulating layer. Both symmetric and asymmetric configurations with equal and different junctions size respectively have been considered. The magnetic field and the voltage dependence of the resonance amplitudes have been compared with the theory reported in the literature.         Zero-field singularities in Josephson tunnel junctions of intermediate length    M. Cirillo, U. Gambardella, S. Pace and B. Savo Summary: Zero-field singularities (Z.F.S.) appear in the d.c. current-voltage characteristic of Josephson tunnel junction longer than the Josephson penetration depth /spl lambda//sub J/. This modes are currently explained in terms of periodical oscillations of fluxons in the junction, and show potential applications in microwave devices. A set of one dimensional overlap junctions of length between 5.6/spl lambda/j and 1.6/spl lambda/j have been studied. Detailed experimental investigations of the current-voltage d.c. characteristics of Z.F.S. are reported. We find that the I-V shape becomes steeper very regularly either by increasing the Z.F.S. order number or by decreasing the junction length. A similar behavior is measured for 2/spl pi/ -kink oscillations on a mechanical analog. Moreover in real junctions anomalous structures appear in high order singularities.         Cooper pairs and quasi-particles tunneling in light-sensitive junctions    L. Bobbio, C. Camerlingo, R. Cristiano, M. Russo and G. Peluso Summary: Tunneling experiments have been performed on lead-cadmium sulphide-lead light-sensitive junctions. In the framework of an equivalent rectangular average barrier model and assuming an effective mass approximation, experimental current-voltage and conductance voltage characteristics have been employed to evaluate the tunneling barrier parameters in dark conditions and at increasing light exposure levels. A parabolic shape for the barrier has been assumed to give a qualitative account for the behavior of the junctions with the light exposure time. Measurements of the temperature dependence of the light-induced dc Josephson current also supports the deviation from the "rectangular" shape of the tunneling barrier at heavy illumination levels.         Effects of fluctuations on Current-Voltage characteristics of Josephson tunnel junctions    A. Barone, C. Camerlingo, R. Cristiano and Yu. Ovchinnikov Summary: Effects of finite capacitance on the Current-Voltage (I-V) characteristics of a Josephson tunnel junction in presence of both thermal and quantum noise have been investigated. The analysis allows the determination of significant features of the I-V curves in different situations.         X-band radiation from Josephson junctions in magnetic field    M. Soerensen, R. Parmentier, P. Christiansen, O. Skovgaard, B. Dueholm, E. Joergensen, V. Koshelets, O. Levring, R. Monaco, J. Mygind, N. Pedersen and M. Samuelsen Summary: Experimental measurements of current-voltage structure and emitted X-band radiation in applied magnetic field from overlap-geometry Josephson tunnel junctions of normalized length about 2 are compared with numerical simulations obtained with the use of a perturbed sine-Gordon model. The simulations furnish the current and field dependence of the oscillation configuration, from which can be calculated average voltages, frequencies, and power spectra. Simulation and experimental results are in good agreement with regard to the lobe structure of the height of the first zero-field step and/or second Fiske step in magnetic field and the field dependence of the radiation frequency within the various lobes, including details such as hysteresis between lobes. The simulations predict an alternation of the dominant frequency component with increasing field that accounts well for the experimental observations.         On the behaviour of a two dimensional Josephson tunnel junction in the weakly non-linear regime    J. Mygind and N. Pedersen Summary: A low-current density - large area, quadratic Josephson junction was investigated. The experimental set-up, designed for the investigation of chaos bifurcations, allowed a measurement of the frequency spectrum up to and above the maximum plasma frequency (/spl omega//sub o//2/spl pi/= 770 MHz) by means of a directly connected low noise 5 - 1000 MHz amplifier. The fundamental cavity resonance frequency (/spl omega//sub c//2/spl pi/) in the linear limit was 4.3 GHz. The non-linear phenomena observed included (i) parametric half harmonic generation with /spl omega/sub pump/ /spl lsim/ 2/spl omega//sub o/(ii) parametric excitation of the plasma mode with /spl omega//sub pump/ /spl sim/spl omega//sub o/+ /spl omega//sub c/ (iii) selfpumped excitation of a "Fiske mode in one direction or a zero field" mode in the other (iv) selfpumped excitation of a two-dimensional mixed "Fiske mode" in a magnetic field. (v) rf induced cavity resonance steps at voltages V = (h/2e)(m/spl omega//sub c/pm n/spl omega//sub pump/) and (vi) usual rf induced /spl omega//sub pump/ /spl omega//sub o. In spite of sufficient receiver sensitivity chaos bifurcations were not observed where simple theory predicts it.         Analytical results for the fluxon-antifluxon annihilation process in Josephson junctions    P. Bodin, N. Pedersen, M. Samuelsen and D. Welner Summary: The perturbation theory for the velocity of fluxons moving on a Josephson line has been extended to junctions of finite length. This is done by including the energy loss during collisions, the bias input energy, and the phase-shift experienced by a soliton approaching a boundary. This enables us to calculate approximate dc IV-characteristics of inline and overlap junctions. These are compared to full numerical simulations. In addition a simple expression for the soliton annihilation curve is given.         Superconducting NbTi and Pb(Cu) bandpass filters    J. Bautista and S. Petty Summary: Superconducting Nb/sub 0.45/>Ti/sub 0.55/and Pb electroplated on Cu bandpass microwave filters have been constructed to investigate their low loss properties at 4.7 K. An interdigital stripline filter configuration was selected as the optimum structure for future applications. The filter was designed to operate at 8.45 GHz with an equal ripple bandwidth of 0.15 GHz. The insertion loss and the noise temperature contribution were measured at 4.7 K. In addition, the insertion loss was studied as a function of out-of-band power (up to 1 watt) and temperature (4.7 K to T/sub c/). Results on an OFHC Cu filter are included for comparison.         Temperature dependence of submillimeter wave response in the point-contact Josephson junction    S. Morita, S. Imai, T. Senoh and N. Mikoshiba Summary: We have measured the magnitude of the first Shapiro step in both bridge-type (Ta-Ta and Ta-Sn) and tunnel-type (Ta-SnOx-Sn) point-contact Josephson junctions in the SMMW ( Submillimeter Wave ) region. By varying the temperature continuously with the frequency of the SMMW fixed (/spl omega/=2/spl pi///spl lambda/, /spl lambda/ = 699, 570 and 469/spl mu/m) . We determined I/sub 1//sup max//I/sub c/minutely as a function of the normalized frequency /spl omega///spl omega//sub g/(T), where I/sub 1//sup max/ is the maximum (half) height of the first Shapiro step as a function of the ac field power, I/sub c/is the critical current, and /spl omega//sub g/(T)=4/spl Delta//sub Ta/(T)/h or 2(/spl Delta//sub Ta/(T)+/spl Delta//sub Sn/(T))/h. By fitting the shape of the Riedel peak at /spl omega///spl omega//sub g/(T)=I with the theory of the tunnel junction, we have determined the damping factor /spl delta/. We obtained /spl delta/ =0.02 for the Ta-SnOx-Sn tunnel- type junction, and /spl delta/=0.05 for both the Ta-Sn and Ta-Ta bridge - type junctions, respectively. At /spl omega///spl omega//sub g/(T>1.5, we have found that I/sub 1//sup max//I/sub c/ tends to saturate in both the tunnel-type and the bridge-type junctions as /spl omega///spl mega//sub g/(T) increases. For the tunnel-type junction, this agrees with the very slow decrease predicted by the theory of the tunnel junction. But for the bridge-type junction, this slow decrease is in marked contrast to the very rapid decrease found from the previous experiments, where the Shapiro step was measuared for a number of frequencies at a fixed temperature.         A more efficient computational procedure for calculating the critical current of a multi-junction superconducting interferometer    C. Lutes, M. Gershenson and R. Schneider Summary: The textbook procedure for the solution of the critical current of an N-junction superconducting interferometer is a 2N-1 dimensional steepest descent problem. A solution by this procedure is complicated by the existence of multiple local minima. The equations are reformulated to reduce the problem to a three-dimensional steepest descent problem. From this reduced equation set, a non-steepest-descent procedure is developed. This technique produces a solution by adjusting a trial critical current value until tangency between a straight line and a special error function is achieved. For a 10-junction test case, an 80-to-1 reduction in computer time was achieved.         Materials and fabrication processes for Nb-Si-Nb SNAP devices    M. Sweeny, M. Gershenson and D. Fleming Summary: Niobium-amourphous silicon-niobium SNAP junction fabrication has demonstrated great technological promise. An aluminum mask gives good resolution to the anodization process and can then be used to pattern an insulating layer self-aligned with the junctions. If the anodization is carried out using a constant-rate voltage ramp and the anodization current is plotted against the anodization voltage, one has an effective analytic tool for studying the niobium and determining an anodization endpoint. We incorporate thin palladium layers in our devices for three purposes. First, the layers provide for resistors while giving superconducting contact through the layer by the proximity effect. Second, the palladium acts as an etch-stop layer so that the top niobium layer can be plasma-etched without damage to the trilayer. A final palladium layer prevents oxidation and makes possible solder contacts to our devices.         Integrated SQUID linear amplifier design and simulation    M. Gershenson Summary: A linear cascade video amplifier capable of working from DC to about one GHz was designed, fabricated, and initially tested. Two asymmetric SQUIDs operating in push-pull are used to achieve linearity and to eliminate output offset. Decoupling of the Josephson oscilliation between the SQUIDs is accomplished by using a special low-pass resonant transformer. Simulation results are presented for three-and ten-junction SQUIDs.         A travelling-wave parametric amplifier utilizing Josephson junctions    M. Sweeny and R. Mahler Summary: Josephson junction parametric amplifiers of travelling-wave design have been designed for use as low-noise millimeter wave amplifiers. These devices have non-reciprocal gain, very wide bandwidths, power dissipations of a few tens of nanowatts, and an input impedance that can be as high as 50 ohms. The design is described and performance estimates, based on a small-signal model, are summarized.         An all-thin-film SQUID for ambient field operation    M. Sweeny Summary: Thin film SQUIDs were constructed in which the aspect ratios of metal lines were controlled, and in which there were no closed loops which couple to a uniform field. The SQUIDs were operated in uniform fields and shown to suitable for use within an integrated magnetic gradiometer system.         Hybrid DC SQUIDs containing all refractory thin film Josephson junctions    D. Fleming, M. Gershenson, R. Hastings, G. Sauter and M. Sweeny Summary: During the past five years Sperry designed, fabricated, and tested DC SQUIDs and feedback transformer assemblies (FTA) for sensor applications. The SQUID design included a silicon chip with deposited, all refractory, thin-film Josephson junctions contained in a bulk niobium toroidal cavity housing. Features include (1) minimum SQUID loop inductance provided by a cone-shaped structure extending from the chip containing the two Josephson junctions to the toroidal cavity where the input coil and concentric modulation coil are housed, and (2) a removable cap that allows easy access to the chip for repair or replacement. This paper presents (1) the design details of the junction chip, niobium housing, and FTA and (2) the flux noise results in the 0.01 to 1,000 Hz frequency range.         Multi-fluxon dynamics in driven Josephson junctions    A. Lawrence, Nung Kim, J. McDaniel and M. Jack Summary: The dynamics of fluxons in a long Josephson junction driven by time-varying non-uniform bias currents are described by a generalization of the sine-Gordon equation. This equation has solitary wave solutions which correspond to current vortices or quantized packets of magnetic flux in the junction. As with the sine-Gordon equation, multi fluxon solutions may be demonstrated for the long Josephson junction. Our numerical calculations show that several fluxons may be launched or annihilated at the end of a junction. We also show multiple steady-state conditions which correspond to one or more flux quanta trapped in the junction.         A rotating superconducting solenoid for 100 kWh energy storage    J. Waynert, Y. Eyssa, G. McIntosh and Z. Feng Summary: Two concentric superconducting solenoids, one rotating, the other stationary are analyzed for energy storage in space. Energy is transferred from the rotating mass through a shaft coupled to a motor-generator. The inner windings interact with the magnetic field of the outer solenoid to cancel the centrifugal and self-field forces of the flywheel rim. Current is induced in the inner solenoid thus requiring no separate power supply, while the current in the outer solenoid must vary with the angular velocity of the flywheel. The effect of the gap and scaling laws are developed. The efficiency in energy per unit mass is marginally attractive.         On-load test of the 20kVA superconducting generator    T. Okada, T. Nitta and T. Shintani Summary: The on-load tests are carried out on an experimental power system, where the 20 kVA superconducting synchronous generator is connected to the regional power system through reactors (artificial transmission lines). The cooling characteristics of the rotor, especially, the cold damper, are obtained. On the on-load tests, active power vs. reactive power, active power vs. load angle, field current vs. active power characteristics at the constant terminal voltage, and so on are obtained. The transient behavior of the generator for a small variation of the input power is obtained. A transient analysis for the above test was carried out. Good agreement between the measured and calculated values is confirmed. From the results, the characteristics of superconducting generators are compared with those of the conventional ones and discussed.         Electromagnetic force analysis on the stator and rotor windings of a superconducting generator    L. Colovini, G. Martinelli and A. Morini Summary: The determination of values and distribution of the forces acting on the components of a superconducting generator is important when designing the machine, particularly in the choice of materials. The paper analyses the electromagnetic forces acting on the field and arma ture windings; for this purpose, with reference to the preliminary design of a two-pole 300 MVA superconducting generator, a two-dimensional analytical method set up by the authors is utilized to calculate the forces on the windings under steady state operation and results are compared with those obtained by means of a numerical meth od.         The investigation of the multi-shielding system of the superconducting generator    Q. Lin and S. Han Summary: In this paper the electromagnetic shielding behavior of the multi-shielding system in superconducting synchronous generators, the influence of one screen upon the others and the sharing of fault moment among the different screens have been investigated. Definition of magnetic penetrability has been made for describing the electromagnetic shielding behaviors of screens. The influence of operation temperature of inner screen on the system was investigated too, and a method of determining the mean temperature of inner screen was proposed.         Three dimensional analysis and experimental studies of fields in superconducting generator with multishield screening system    Feng Er-Jian Summary: In this paper a new three dimensional analytical method for computing the fields in superconducting generator with multishield screening system is developed, All the quantities we are interested in can be obtained without solving the simultaneous equations numerically. The accuracy of theoretical computation is verified by experiments and the agreement is satisfactory.         Design and construction of a 20W/1000A cryogenic power supply    J. Sikkenga, W. Brandhorst, J. Knoben and H. ten Kate Summary: In order to meet the requirements for accurate and low power supplies for superconducting applications, a 20W/1kA cryogenic power supply was designed and constructed. It is a full-wave superconducting rectifier, and is taken as a starting point for further developments. The superconducting part consists of an air core transformer and thermally controlled superconducting switches. To operate the system Holec constructed an electronic control unit. The rectifier was tested by using a small 17.5mH coil and an 0.5T NMR magnet. The small coil was loaded to 750A; the current was limited by quenches in the load coil. The average power of the rectifier was measured at several currents . Experiments show that the efficiency is higher than 97%. From the experiments it was concluded that in general the performance of the rectifier is according the design specifications.         A fast operating magnetically controlled switch for 1 kA    G. Mulder, H. ten Kate, A. Nijhuis and L. van de Klundert Summary: The power of fully superconducting rectifiers can be improved by increasing either the operating frequency or the transformer primary inductance [1]. The frequency is usually limited by the recovery time of thermally controlled switches. In order to achieve a higher switching speed, magnetically controlled switches are preferable [1,2]. This paper describes a magnetically controlled switch which can be used for currents up to 500 A at 25 Hz. The switch element, consisting of several Nb1%Zr multifilamentary superconductors, is placed between two concentric solenoids which generate the necessary magnetic field. The Nb1%Zr superconductor is well suited for this purpose because of its relatively low critical field (/spl sime/ 0.75 T) and high maximum current density (about 5.10/sup 9/A/m/sup 2/below 0.3 T).         Superconducting magnets for electromagnetic d.c. pumps    P. Del Vecchio, A. Geri and G. Veca Summary: The authors have carried out an analysis of the performances of a d.c. electromagnetic pump with a superconductive field magnet (SCEMP). The importance is stressed of the introduction of an algorithm capable of evaluating the power losses in the conducting fluid outside the magnet; the electromagnetic efficiency of the pump is further analyzed, by varying the length of the magnet itself as well as the spatial distribution of the magnetic flux density.         Applications of a superconducting magnet on high performance Fourier transform mass spectrometers    Y. Huang and J. Kinsinger Summary: Ultra-high mass resolution; easy mass calibration routines; accurate mass measurement; wide mass range; high sensitivity; and the ability to rapidly perform experiments and to rapidly change experiments are the special features that make a Fourier transform mass spectrometer (FTMS) highly productive as an analytical mass spectrometer. An FTMS requires a relatively high magnetic field, a large homogenous volume and long term field stability; the requirements only a superconducting magnet can fulfill. We have designed a superconducting magnet to provide the required magnetic environment for our FTMS system. The central field of the magnet is 3T. The 100 ppm homogeneity volume is 5 cm X 5 cm X 10 cm. The Iield stability is 1 ppb/hr. The integrated cryostat design allows the whole system to be installed and operational within thirty-six hours in the field. The reproducibility of the magnet has been perfect.         Field correction of a high-homogeneous field superconducting magnet using a least squares method    S. Yamamoto, T. Yamada, M. Morita, T. Matsuda and M. Iwamoto Summary: A 6th order superconducting solenoid coil has been developed for a whole body magnetic resonance imaging. Nine sets of shim coils are equipped on the solenoid coil. A least squares computer program was applied to determine shim coil currents analytically. After the field correction using shim coils, the homogeneity of 7.6x10/sup -6//30cm DSV was obtained. The effects of ferromagnetic objects on the homogeneity was studied. The error field caused by iron spheres agreed well with the theoretical results. It was found that ferromagnetic objects generated mainly the 1st order error field and this could be corrected by shim coils. The effects of heat and charge/discharge cycles of the magnet on the homogeneity was studied.         Quench experiments on superconductive coils    N. Maene, J. Cornelis, F. Biermans and A. Van den Bosch Summary: A set of four similar superconductive coils of 166 mm inner winding diameter were wet-wound with NbTi wire for subsequent application in various configurations: one single coil, a pair of coils or all four coils stacked on top of each other and connected in series. The height of the winding was 41 mm and the thickness 9 mm. The detailed observation of the time-dependence of the current and voltage with a data processing system yielded information on the time scale of the quench propagation. In the single coil and the pair of coils the time dependence of the quench resistance with time was derived from an analysis of the current and the coil voltages during the transient. With the four coils the time required for the current to decrease from 90 % to 10 % gets shorter with increasing quench current. Variations of 1.6 s to 0.3 s were observed in this configuration. At the maximum current a magnetic induction of at least 2.5 T was reached in a volume of over 2.5 litres. The self-inductance of this system was 1.28 Henry and the stored energy attained 22 kJ.         Mechanical properties of superconducting coils    J. Carson and F. Markley Summary: Experience with the present generation of Tevatron superconducting magnet coils has made apparent several areas of possible improvement of coil structure. Implementation of the structural changes; i.e., cabling, insulation, adhesive, etc., requires a new determination of coil mechanical properties. In particular, measurements to enable prediction of coil stresses from the dimensions of coil substructures and prediction of residual stresses as a result of magnet storage and operational conditions. Theoretical uncertainties, because of the complex geometries, make empirical measurements desirable. We will measure the relationship between assembly stress and the component dimensions for several coil structures. From this data and the allowable design stress levels, component dimensions can be set. We have also measured the effect on stress levels of storage for protracted periods at high ambient temperatures and of operational occurrences such as a forced warm up which will substantially elevate temperatures for short periods. This data makes it possible to predict the number and severity of such occurrences that can be tolerated.         Three-terminal superconducting devices    W. Gallagher Summary: The transistor has a number of properties that make it so useful. We discuss these and the additional properties a transistor would need to have for high performance applications at temperatures where superconductivity could contribute advantages to system-level performance. These properties then serve as criteria by which to evaluate three-terminal devices that have been proposed for applications at superconducting temperatures. FETs can retain their transistor properties at low temperatures, but their power consumption is too large for high-speed, high-density cryogenic applications. We discuss in detail why demonstrated superconducting devices with three terminals - Josephson effect based devices, injection controlled weak links, and stacked tunnel junction devices such as the superconducting transistor proposed by K. Gray and the quiteron - each fail to have true transistor-like properties. We conclude that the potentially very rewarding search for a transistor compatible with superconductivity in high performance applications must be in new directions.         Gap suppression devices    B. Hunt, R. Robertazzi and R. Buhrman Summary: In this paper we discuss some general features of three terminal superconducting devices which operate on the basis of superconducting energy gap suppression by quasiparticle injection. These features include latching behavior at greater than unity power gain and, in the conventional three layer sandwich geometry, a rather long device switching time. We then describe three terminal gap suppression experiments carried out with the use of a double edge junction geometry. The problems of obtaining large gain in this higher speed geometry are discussed. Finally, we point out that these problems are alleviated by using the gap suppression effect to switch a supercurrent biased junction rather than to modify the quasiparticle I-V curve.         A new superconducting-base transistor    D. Frank, M. Brady and A. Davidson Summary: The continuing search for a good cryogenic transistor has led to a new proposal, the superconducting-base semiconductor-isolated transistor (SUB-SIT). This three-terminal device is expected to have characteristics very similar to those of bipolar transistors, but at millivolt operating levels. We present discussions of the concepts involved in the SUBSIT, proposed fabrication techniques, and theoretical results for its DC and high frequency characteristics.         Miniaturization of Josephson logic circuits    H. Ko and T. Van Duzer Summary: The performances of Current Injection Logic (CIL) and Resistor Coupled Josephson Logic (RCJL) have been evaluated for minimum features sizes ranging from 5 /spl mu/m to 0.2 /spl mu/m. The logic delay is limited to about 10 ps for both the CIL AND gate and the RCJL OR gate biased at 70% of maximum bias current. The maximum circuit count on an 6.35 X 6.35 chip is 13,000 for CIL gates and 20,000 for RCJL gates, Some suggestions are given for further improvements.         A dense voltage-mode Josephson memory cell insensitive to systematic variations in critical current density    P. Bradley and T. Van Duzer Summary: A destructive read-out (DRO) memory cell using three Josephson junctions has been devised whose operation depends only on the ratio of critical currents and application of the proper read/write voltages. The effects of run-to-run and across-the-wafer variations in I/sub c/are minimized since all three junctions for a given cell are quite close to each other. Additional advantages are: immunity from flux trapping, high circuit density, and fast switching. Since destructive read-out is generally undesirable, a self-rewriting scheme is necessary. Rows and columns of cells with drivers and sense circuits, as well as small memory arrays and decoders have been simulated on SPICE. Power dissipation of cells and bias circuits for a 1K-bit RAM is estimated at about 2 mW. Inclusion of peripheral circuitry raises this by as much as a factor of five depending on the driving scheme and speed desired. Estimated access time is appreciably less than a nanosecond. Preliminary experimental investigations are reported.         Fabrication and performance of all refractory josephson logic circuits for 1 Kbit SFQ memory    S. Tahara, S. Kosaka, A. Shoji, M. Aoyagi, F. Shinoki and H. Hayakawa Summary: All refractory Josephson loop logic circuits for a 1Kbit SFQ memory have been developed. The circuit fabircation technology, using NbN/Nb double layered junction formation and reactive ion etching(RIE)with a 2.5/spl mu/m minimum feature size and 1.5/spl mu/m overlay registration, has been utilized. A highly selective and anisotropic RIE process has been performed, in which a CCl/sub 2/F/sub 2/+ Ne gas mixture has been used as etching gases. The experimental circuit consists of address decoders and line drivers, which are based on the principle of current steering in superconducting loops. The decoder and driver were successfully operated with the gate current margin of /spl plusmn/18% and /spl plusmn/14%, respectively. The decoder internal delay time was measured to be about 1.5 ns. It is revealed that these circuits have a satisfactory preformance to be used in the 1Kbit SFQ memory.         Real time fluxon dynamics in josephson transmission line    H. Akoh, S. Sakai, A. Yagi and H. Hayakawa Summary: Dynamics of fluxons propagating in a Josephson transmission line (JTL) have been studied in real time using Josephson sampling techniques. A JTL is an NbN-oxide-NbN Josephson junction with dimensions of 2.5 X 150 /spl mu/m/sup 2/, while Josephson samplers and pulse generators for generating and driving fluxons are fabricated by a Pb-alloy technology. Among the various behaviors, especially, it is found that a propagating fluxon can be made to pause without reflections at any desired position which is created by placing a resistor on the surface of a portion of a JTL. The surface resistor has a length larger than the Josephson penetration depth. A pausing fluxon can be re-driven by supplying a small current to the portion of the surface resistor after more than 100 /spl mu/s, The experimental results are compared with computer simulations. Reflections of fluxons observed by samplers have also been discussed.         Low crosstalk packaging design for Josephson logic circuits    K. Aoki, Y. Tazoh and H. Yoshikiyo Summary: Theoretical and experimental studies are accomplished for inductive crosstalk noise reductions at Josephson chip-to-card connectors. This noise is induced by large AC power and high switching speed signal currents. The crosstalk mechanism was analyzed using a Partial Element Equivalent Circuits Model. Ground inductance causes not only crosstalk noise between connectors but also ground fluctuation noise inside the chip. This ground noise is large enough to cause false logic operations. Test chips and cards with improved connectors were produced for an experimental evaluation. Power crosstalk noise was measured using Josephson sampling circuits fabricated on the chip. The crosstalk noise - signal level ratio was less than 2.5%, when 250 MHz, 50 mA power currents were supplied. Crosstalk noise between neighboring signal connectors was also reduced to negligible level, including the worst case. These results favorably agree with calculations. This low crosstalk packaging design can be applied to high speed Josephson logic systems.         Superconducting qualification program for TFCX and Alcator DCT magnetic systems    D. Montgomery Summary: The purpose of the Magnetics Qualification Program is to demonstrate the feasibility of ICCS conductors for TF and PF coils for TFCX and DCT. Conductor requirements for these projects represent an advance over LCP conductors in peak field, overall current density, and in strand-to-strand decoupling. Achievement of these advanced parameters results in significant device performance improvement and cost savings over the performance achievable with the LCP ICCS westinghouse/Airco Conductor.         Magnetic to kinetic energy conversion following structural failure    R. Thome, R. Pillsbury, W. Langton and W. Mann Summary: A magnet failure which is potentially catastrophic in the sense that structural components fracture and the winding suffers extensive plastic deformation can be "safe" under special conditions. It may be desirable to limit operating current densities to levels at which the winding could act to limit magnetic to kinetic energy conversion. A solenoid model was used to analyze and determine the important governing parameters in the failure and discharge process. The conclusions are: (a) A protective circuit reaction involving resistive dissipation following a major structural failure is unlikely to be effective on a fast enough time scale in high current density windings. (b) Windings with low enough current densities can absorb the total load following structural failure, thus limiting the kinetic energy conversion process, although this might involve substantial yielding and deformation of the winding. (c) Protective circuits involving inductive energy transfer can respond fast enough to limit the kinetic energy conversion process in high or low current density configurations and are effective provided they are well coupled to the primary circuit.         Operation of the 30 MJ superconducting magnetic energy storage system in the Bonneville Power Administration electrical grid    J. Rogers, H. Boenig, R. Schermer and J. Hauer Summary: The 30 MJ superconducting magnetic energy storage (SMES) system was installed in the Bonneville Power Administration (BPA) Tacoma Substation in 1982-83. Operation of the unit since that time has been for over 1200 hours. Specific tests to explore the SMES system's thermal and electrical characteristics and the control functions were conducted. The coil heat load with current modulation was determined. A converter with two 6-pulse bridges interfaces the superconducting coil to the power bus. Equal bridge voltage amplitude and constant reactive power modes of operation of the system were run with computer control of the SCR bridge firing angles. Coil energy dump tests were performed. Electrical grid system response to SMES modulation was observed, and full power SMES modulation was undertaken.         Nb-Al powder metallurgy processed multifilamentary wire    C. Thieme, S. Pourrahimi, B. Schwartz and S. Foner Summary: Powder metallurgy processed Nb-Al wire with overall critical current densities, J/sub c/, at 4.2K up to 10/sup 4/A/cm/sup 2/at 19T has been investigated in more detail, Kramer plots and directly measured H/sub c2/values of samples with different heat treatments show an increase in H/sub c2/at 4.2K up to 24.5T. Test coils, using long lengths of wire, and tested in fields up to 15T, show J/sub c/values equal to those of short samples. Multiple strand hydrostatic small scale extrusions were made. A number of third element additions including B, Mg, Co, Cr and Ni in fine powder form were incorporated in the P/M processing but these did not improve J/sub c/. ac losses were measured and used to determine J/sub c/at 10w fields. The high field ac losses are lower than that for any In Situ or powder processed Nb/sub 3/Sn wires.         Studies on structure and properties of in-situ V/sub 3/Ga superconducting composite tapes    H. Kumakura, K. Togano, T. Takeuchi and K. Tachikawa Summary: Recent scaling-up development of the in-situ processed V/sub 3/Ga composite superconductor at NRIM is reported. Cu-V binary ingots were prepared by consumable arc-melting, and cold-worked into tapes of 100-300m in length. Inspection of the uniformity was carried out for the in-situ Cu-V tapes by measuring the electrical resistivity change at room temperature along the tape length, and the results were compared with the critical current density J/sub c/distribution of the final in-situ V/sub 3/Ga tapes. The structure of the in-situ tapes, obtained by continuous Ga-dipping and diffusion heat treatment, were studied. The reacted layer is divided into two layers with different V/sub 3/Ga morphology. The outer layer composed of globular V/sub 3/Ga has a T/sub c/of 15.2K, while the inner layer composed of ribbon-like filamentary V/sub 3/Ga has somewhat lower T/sub c/of 15-13.5K. Therefore, the observed J/sub c/characteristic is a combined contribution from both layers having a different magnetic field dependence of J/sub c/. The ribbon-like morphology in the inner layer is responsible for the J/sub c/anisotropy of the tapes. The J/sub c/-H characteristics of the in-situ V/sub 3/Ga tape revealed by the present study are advantageous in constructing 15-17 Tesla class superconducting magnet.         Powder metallurgy processed Nb/sub 3/Sn employing extrusion and varying Nb content    S. Pourrahimi, C. Thieme, B. Schwartz and S. Foner Summary: Extension of powder metallurgy (P/M) processing of Cu-Nb-Sn is described for small scale industrial uniaxial extrusion (R /spl les 10/sup 4/) and for small scale hydrostatic extrusions for areal reductions R = 2000. Successful 2.5 cm o.d. uniaxial P/M processed extrusions at 950 and 250/spl deg/F were obtained. Model cold hydrostatic extrusions of single tin core and multitin core wire are described. The effect of Nb content for Cu-x wt% Nb, where 36 /spl les/ /spl times/ /spl les/ 60was examined. Increased over-all critical current densities, J/sub c/were obtained with increased Nb content up to 50 wt% Nb. For proper comparisons, values of J/sub cm/(where the prestress is removed), are given for several compositions. Improvement in J/sub c/for T /spl les/ 4.2K is also presented. Incorporation of Tl in Nb/sub 3/Sn by means of Sn-Ti core processing results in further increases in J/sub c/. The low R and large initial powder sizes result in relatively thick Nb fibers which are not completely reacted. The present extrusion P/M processed wires demonstrate several practical approaches for development of high performance materials. Optimization should yield high values of J/sub c/at 20 tesla.         The effect of non-hydrostatic strain on the superconducting properties of in-situ formed Cu-Nb/sub 3/Sn filamentary composites    J. Bevk, W. Sunder, F. Hellman and T. Geballe Summary: The effect of both hydrostatic and nonhydrostatic strains on the intrinsic properties of A15 compounds is well known; however, because of the experimental difficulties the underlying mechanisms are only poorly understood. In this study, we make use of the large elastic strains in the in-situ formed Cu-Nb/sub 3/Sn filamentary composites due to differential thermal contraction. These strains can be greatly reduced by plastically deforming the sample and hence one can measure the properties of otherwise identical samples in two distinctly different stress states. The increase (upon deformation) in H/sub c2/(2.1 Tesla) and in T/sub c/(0.6K) is correlated with small but significant changes in the low-temperature heat capacity data. These changes are attributed to the increase in the density of states of Nb/sub 3/Sn phase rather than to the lattice heat capacity. Changes in the critical current I/sub c/are shown to be entirely due to the increase in H/sub c2/.         Further investigations of the solid-liquid reaction and high-field critical current density in liquid-infiltrated Nb-Sn superconductors    M. Hong, D. Maher, M. Ellington, F. Hellman, T. Geballe, J. Ekin and J. Holthuis Summary: Superior superconducting properties, such as high J/sub c/'s and T/sub c/'s, have been obtained from reacted liquid-infiltrated Nb-Sn composite wires. These excellent properties are attributed to the chemistry and structure of the material, which is prepared by a unique solid (Nb) - liquid (Sn) reaction. From heat capacity measurements, sharp bulk superconducting transitions of the Al5 phase occur at 17.2-18 K and the weight fraction of Al5 in the composite wire is ~23%. Analytical electron microscopy techniques have shown that: the microstructure of these conductors consists of alternating large-grain and small-grain filaments; these two types of filaments correspond to BCC Nb(Sn) and cubic Al5 Nb/sub 75/spl plusmn/x/ Sn/sub 25//spl mnplus/x phases, respectively; the Al5 filaments (/spl les/0.5 /spl mu/m) are chemically homogeneous in terms of measured X-ray intensity ratios to within /spl plusmn/7%, which implies that x/spl sim/1.5; and the Al5 grains are essentially free of extended lattice disorder down to a resolution of /spl sim/0.34nm. Recent work in which Nb is alloyed with Ta has shown that these superconducting properties can be improved upon; e.g. high overall J/sub c/'s of /spl sim/1.8 /spl times/ 10/sup 4/ A/cm/sup 2/at 20 T and 4.2 K have been measured. Also, the liquid-infiltrated Nb(Ta)-Sn composites have a damage strain tolerance nearly double that of commercial bronze-processed Nb-Sn conductors.         Strain effects in cabled and braided "in situ" formed Nb/sub 3/Sn conductors    T. Okada, M. Fukumoto, K. Yasohama and K. Yasukochi Summary: Three-strand cables (pitch=15 and 30 mm) and three-strand braid (pitch=30 mm) have been made using "in situ" formed Nb/sub 3/Sn wire (0.31 mm outer diameter) as strands, and their mechanical properties and strain effects have been investigated. The stress-strain relations of all the cables and braid examined are similar to that of the strand except in lower strain region. The degradations in the critical currents are observed for the cable with smaller pitch and the braid. Strain sensitivity of critical current is enhanced by braiding. The optimization of the pitch is required for cables and braids in order to fully utilize high critical current and high strain tolerence of "in situ" formed strands.         Neutron irradiation effects on in situ Nb/sub 3/Sn superconducting wires    Y. Hirano, S. Nishijima, M. Fukumoto, T. Okada, H. Kodaka and H. Yoshida Summary: Three types of "in situ" Nb/sub 3/Sn conductors have been studied to determine the detrimental effects of neutron irradiation on critical temperature, critical current and AC losses. It was found that at fluences of 10/sup 18/n/cm/sup 2/, the critical temperature is degraded by approximately 10 %. Degradation of AC loss is discussed in comparison with that of critical current density.         30 MVA superconducting synchronous condenser: Design and it's performance test results    S. Nakamura, T. Yamada, T. Nomura, M. Iwamoto, Y. Shindo, S. Nose, A. Ishihara and H. Fujino Summary: 30 MVA superconducting synchronous condenser has been designed, fabricated, and tested successfully. The test suggested that the new approaches applied to the 30 MVA machine were reasonable. The superconducting field winding composed of six Nb-Ti and two Nb/sub 3/Sn coils, supported in torque-tube slots by wedges, was excited up to the rated operating current without training. The amplitudes of the rotor vibration were small and special balance at cryogenic temperature was not needed. In this paper, the studies on the key design aspects, namely, superconducting field winding, rotor structural materials, and rotor structures including the connection means between torque-tube(cold) and damper(warm) are described together with the experimental verifications. Moreover, the stator design and the electro-magnetic design including an analysis of the operational performance with regard to double damper system are presented. Machine constants obtained from the theoretical investigations using three-dimensional electro-magnetic field calculations are in good agreement with test results.         Construction of MIT-DOE 10-MVA superconducting generator    J. Smith and A. Liepert Summary: A 10-MVA synchronous alternator has been designed and constructed to demonstrate advanced concepts for power station generators with superconducting field windings in the rotor. The experimental generator is in the final stages of assembly in preparation for no load tests and a 30-day full load test. This paper describes the construction of the generator, including the details of the superconducting rotor with emphasis on the unusual features. Problems in fabrication and assembly are discussed.         Operational characteristics of a 1000 MVA superconducting power transmission system    R. Thomas Summary: Over the last three years, the power transmission project at Brookhaven National Laboratory has been testing two flexible superconducting cables for the transmission of ac electric power. These cables are each 115 m long and are rated at 80 kV, 4100 A single-phase for a power rating of 333 MVA- (1000 MVA, 138 kV, 3 phase). They have been operated over the range of 7-12 K in supercritical helium at 14-15 atm. The cables have been tested at currents and voltages above their ratings and have also been operated with no coolant flow to study the effects of loss of refrigeration on cable performance. The insights gained from the operating of the system over this extended period will be presented. Finally, we will delineate those areas which will require further research before this technology can be integrated into the U.S. electrical power delivery system.         DC and pulse operations of 4 MJ pulsed superconducting magnet and its stress analysis    T. Onishi, H. Tateishi, K. Koyama and C. Suzawa Summary: 4 MJ pulsed magnet was tested in dc and pulse operating modes, It was successfully charged up to 5940 A ( 4.6 MJ, 6.9 T) at 0.15 T/sec and discharged at 3.5 T/sec without quenching. Strains due to hoop stress were measured and analysed using a spring model. It is pointed out that they do not necessarily propagate from turn to turn and hence the strains measured at the outer support band may be small. A residual compressive force in the magnet windings was also analysed. Ac losses were measured using a 3 MJ pulsed magnet having almost the same structure and conductor as 4 MJ magnet and shown to be fairly small.         Test results of high ramp rate pulsed superconducting coil for the reacting plasma tokamak    T. Satow, M. Iwamoto, K. Toyoda, T. Ogasawara, Y. Kubota, T. Makiura, K. Yasukochi, H. Momota, K. Sato, S. Yamada, T. Onishi, K. Koyama, O. Tsukamoto and T. Yoda Summary: A model pulsed coil (RPC-II) with an average ramp rate of 200 T/s has been built and tested in order to meet the requirements of superconducting poloidal coils of medium size tokamaks. The inner and outer diameters of the coil are 19.0 and 47.2 cm, respectively, with an axial length of 43.1 cm. The coil has a solenoid winding with a layer to layer cooling spacing of 2.2 mm and insulation sheets between layers. The pulsing tests were performed by a capacitor discharge method with a crowbar circuit. By applying a terminal voltage of 7.6 kV, the field was raised up to 3.9 T in 19 ms, slightly increased up to the maximum field 4.0 T in about 120 ms from the start, and decayed with a time constant of 450 ms. This mode simulates the operation of ohmic heating coils. The average and maximum pulsing rates in charge-up period were 200 T/s and 314 T/s, respectively. The associated a.c. loss per pulse was about 400 J which was only 0.3 % of the energy stored in the coil. After twelve pulses with a repetition period of 15 min., no change in the pulsing characteristics of the coil has been observed. These results showed the scientific feasibility of superconducting poloidal coils to be used in long-pulse medium size tokamaks.         The origin of prestress in binary and ternary Nb/sub 3/Sn multifilamentary wires    W. Goldacker and R. Flukiger Summary: High resolution neutron powder diffractometry at temperatures between 10 K and 800 K was performed on commercially available Nb/sub 3/Sn multifilamentary superconducting wires with additions of 1.6 Ti, 0.5 Ti and 7.5 Ta (wt.%), and with internal steel reinforcement as a continuation of our earlier work upon binary Nb/sub 3/Sn conductors. In addition to still well characterized stress induced lattice distortion T/sub 2/a volume compression of the unit cell caused by hydrostatic compression of the filaments by the surrounding bronze was observed for the first time. The volume compression (up to 0.4 %) was derived from a quantitative comparison with the results of high resolution X-ray measurements of etched filaments, where only thermal contraction is acting. Both lattice deformations are of the same order of magnitude and both stress induced effectS, the tetragonal distortion and the hydrostatically volume compressien were found to be reduced by ternary additions. Internal steel reinforcement seems to act dominantly by hydrostatic volume compression. Therefore the combination of this two effects is responsible for the prestress and the correlated J/sub c/degradation.         Martensitic phase transformation in Nb/sub 3/Sn-x-ray observations    R. Roberge, H. LeHuy and S. Foner Summary: A compilation is presented of room temperature lattice spacing, a/sub o/, versus martensitic phase transformation temperature, T/sub m/, of Nb/sub 3/Sn for over 50 set of data including data of other investigations. The low temperature tetragonal phase transition occurs with c/a < 1 for a/sub o/between 5.289 and 5.2933 /spl Aring/, with c/a > 1 for a/sub o/between 5.2865 and 5.2883 /spl Aring/. Nb/sub 3/Sn remains in the cubic phase (no transformation) for a/sub o/< 5.2865 /spl Aring/ and a/sub o/> 5.2933 /spl Aring/, and for a very narrow region between 5.2883 /spl Aring/ and 5.289 /spl Aring/. The effect of additives and the effect of matrix strain on the width of T/sub m/is also discussed. A detailed tabulation is presented for the various Nb/sub 3/Sn materials and their resultant transformation characteristics.         Characterization of Nb-8 wt.% Al wires by analytical electron microscopy    W. King, C. Thieme and S. Foner Summary: Analytical electron microscopic observations of longitudinal cross-sections of Nb-8 wt.% Al powder metallurgy processed wire are presented. Grains were found of unreacted Nb, Nb-Al which was identified as Al5 Nb-Al by convergent beam electron diffraction (CBED), and Nb-Al grains identified as Nb/sub 2/Al by CBED. No unreacted Al is found. High resolution TEM views for each phase and for regions at the phase boundaries are also presented. Comparisons of the composition of arc melted Nb/sub 3/Al are made with the low temperature P/M processed Al5 phase.         New phase formation and superconductivity in reactively diffused Nb/sub 3/Sn multilayer films    J. Vandenberg, M. Gurvitch, R. Hamm, M. Hong and J. Rowell Summary: Thin films of A15 Nb/sub 3/Sn have been prepared by reactive diffusion of sputter-deposited Nb/Sn multilayers. The layer thicknesses were arranged in such a way as to produce Nb/sub 3/Sn and desired off-stoichiometry samples. The reaction was studied by means of in situ temperature-dependent X-ray analysis in the range 50/spl deg/C-950/spl deg/C. It was observed that, prior to the formation of the Al5 phase, a very rapid reaction takes place between the Nb sublayers and molten Sn. In this reaction a new phase was observed which could be interpreted as a hexagonal Laves phase NbSn/sub 2/. This phase transforms into orthorhombic NbSn/sub 2/which then reacts with the remaining Nb to form Al5 Nb/sub 3/Sn. The fact that the reaction occurs at the Nb/liquid Sn interface with the formation of the most Sn-rich phase indicates that the reaction takes place by diffusion of Nb into liquid Sn. The highest superconducting transition temperature was found to be 17.45/spl deg/K. The values of the Al5 cell parameters indicated that the diffusion reaction of both on-and off - stoichiometry Nb/sub 3/Sn multilayers is driven towards the Sn-rich side of Nb/sub 3/Sn, with a maximum composition range of 24-28 at% Sn.         Annealing of heavy ion irradiated Nb/sub 3/Ge films    H. Kramer, W. Schauer, H. Wuhl, C. Nolscher, H. Adrian and G. Saemann-Ischenko Summary: High T/sub c/Nb/sub 3/Ge films prepared by coevaporation have been irradiated by 20 MeV sulfur ions at low temperatures (< 25 K). X-ray analysis showed an expansion of the Al5 lattice and an increasing degree of amorphicity, while T/sub c/vs. dose decreased from 22 K to 4.3 K with a slight minimum of /spl sim/70 mK depth at /spl phi/ t/spl sim/ 3.10/sup 15//cm/sup -2/before saturation. - Filmsirradiated by doses up to /spl les/ 1.5 /spl middot/ 10/sup 15/cm/sup -2/could be annealed to the pre-irradiation T/sub c/. In contrast, strong irradiation led to an (X-ray-) amorphous structure, from which T/sub c/values of only 15-17 K could be recovered, similar to the results obtained for amorphous NbGe films condensed at LN/sub 2/temperature. - The behaviour of the film resistivity during the heat treatment indicates that for films irradiated by low doses only lattice defects anneal, whereas for high dose damaged films recrystallization from the amorphous state occurs.         An approximate closed-form expression for the electron-scattering-induced interaction between magnetic flux lines and grain boundaries    D. Welch Summary: An approximate closed-form result for the interaction of an isolated magnetic flux line in a type-II superconductor with a grain boundary, due to the scattering of electrons by the boundary, is presented here. The grain boundary need not be infinitely thin, but can include a distribution of scattering centers nearby. The resulting expressions are more suitable for computer simulations of flux pinning and their interpretation is more physically transparent than previous results; they are used here to discuss pinning by nonideal boundaries.         Time dependence of magnetic flux penetration in Nb and Nb/sub 3/Sn    S. Ghamati, H. Suhl, W. Vernon and G. Webb Summary: We have investigated a single crystal sample of Nb/sub 3/Sn at low frequencies, 100 Hz to 13 kHz, and found a value of B/sub c1/= (45.6 /spl plusmn/ 2.7)mT for the lower critical field extrapolated to T /spl sime/0K at 497 HZ. The critical field, as we have defined here, was observed to increase by 32 /spl plusmn/ 5% in going from 0.5 to 13 kHz. Hysteretic energy loss was used to determine the critical fields and was observed to decrease rapidly with frequency, dropping a factor of ten between 0.5 and 13 kHz. Samples of Nb wire were pulsed with field rise times of 2 /spl mu/sec and found to have a T /spl sime/0K value of B/sub c1/= 158 /spl plusmn/ 8 mT, unchanged from lower frequency values. The Nb/sub 3/Sn sample had undetectable signal levels under similar pulse conditions (up to 150 mT maximum field). Temperature dependence of the critical fields is consistent with 1 - (T/T/sub c/)/sup 2/behavior from 2 K to T/sub c/(18.0/spl plusmn/0.1 K for the Nb/sub 3/Sn sample).         Reactive evaporation of Chevrel phase superconducting compounds    R. Webb, A. Goldman, J. Kang, J. Maps and M. Schmidt Summary: Thin films of Chevrel phase compounds CuMo/sub 6/S/sub 8/and HoMo/sub 6/S/sub 8/have been formed using a reactive evaporation technique in which the metallic constituents are derived from either electron-gun or resistively heated sources and S vapor is obtained from a molecular beam oven. The constituents are reacted on a sapphire substrate kept at elevated temperatures. Compositional uniformity is insured by controlling the S rate and locking the rates of the other sources to it in a prearranged fashion. The evaporation system used in this work is equipped with a vacuum lock which permits substrates to be changed without reprocessing the system. CuMo/sub 6/S/sub 8/films produced using these techniques are relatively pure and well-ordered. HoMo/sub 6/S/sub 8/films show a resistance minimum but do not become completely superconducting as prepared, but do so after reactive annealing. These methods have not been used successfully to form PbMo/sub 6/S/sub 8/films because of the high volatility and short dwell time of Pb on the substrate surface.         Superconductivity in FCC Mo/sub x/Nb/sub 1-x/(N/sub y/C/sub 1-y/)/sub z/thin films    S. Wolf, S. Qadri, K. Kihlstrom, R. Simon, W. Fuller, D. VanVechten, E. Skelton and D. Gubser Summary: In an attempt to prepare the predicted high superconducting transition temperature material MoN, films of Mo/sub x/NB/sub 1-x/(N/sub y/C/sub 1-y/)/sub z/where 0.93>x>0, 1.0>y>0.8, and 1.0>z>0.5, have been prepared in a UHV system by reactive rf sputtering of a split Mo-Nb target in mixtures of argon, nitrogen and cyanogen gases. These films prepared at elevated temperatures (600- 800 C) are all single phase FCC (Bl) structure with varying amounts of nitrogen deficiencies. The lattice parameter and Tc are smoothly varying functions of composition with a maximum T/sub c/of 18 K for NbN/sub 0.8/C/sub 0.2/T/sub c/initially decreases with increasing Mo content reaches a minimum and begins to increase on the very Mo rich composition side where the nitrogen deficiencies in the structure are significant. Nitrogen implantation increases the lattice properties of the Nb rich samples.         Superconducting properties of sputtered Mo-C films with columnar microstructure    J. Wood, J. Keem, J. Chen, A. Kadin, R. Burkhardt and S. Ovshinsky Summary: We have fabricated Mo/sub x/C/sub 1-x/thin film samples by sputtering, and have studied the dependence of superconducting critical temperatures, fields, and currents on composition and microstructure. For x in the range from 40-60%, the preferred nonequilibrium Mo-C Bl phase (with T/sub c/up to 13K) grows in an oriented columnar structure, with column diameters of 100-1000/spl Aring/. This is correlated with sharply enhanced perpendicular critical fields (with extrapolated values of H/sub c2/(O) that can exceed 300kOe) together with a critical current density that may be as large as 10/sup 6/A/cm/sup 2/. We also present data on artificial layered structures based on Mo-C, fabricated either by alternately sputtering Si layers or by pulsed gas injection of N/sub 2/.         Fabrication of a miniaturized DCL OR gate    R. Ono, J. Beall and R. Harris Summary: Using niobium edge junctions and electron beam lithography (EBL) we have made direct coupled logic (DCL) OR gates with 1 /spl mu/m minimum line widths. The gate cell, containing an isolator and a buffer section, fits into an area of approximately 25 by 30 /spl mu/m/sup 2/. Our computer simulations show that these gates can have switching times of less than 10 ps. We have simulated the DCL circuit with several values of the most space-consuming element, an inductor. This paper describes the results of these simulations and presents a detailed description of the 7-level fabrication process. The mix of optical and electron-beam lithography used relies heavily on an inexpensive, yet powerful, circuit layout program.         Critical current behavior and oxide barrier properties of Ta surface layers on Nb    S. Ruggiero, G. Arnold, E. Track and D. Prober Summary: We have investigated the critical current, I/sub c/R, and oxide barrier shape in Nb/Ta/Ox/C.E. tunnel junctions. Here, layers of Ta in the thickness range O\bar{\phi}, and width, s, of the oxide barriers which form on the Ta overlayers. It is observed empirically that\bar{\phi} /spl sim/6/(s-s/sub o/)where s/sub o/ /spl sim/10/spl Aring/ and /spl phi/ is measured in eV. This relationship is also found to hold for barrier formation on a wide variety of pure and composite metallic systems. These results are discussed in conjunction with the Fromhold-Mott-Cabrera theory for self-limiting oxide growth on metal surfaces.         Length dependent properties of SNS microbridges    J. Sauvageau, R. Ono, A. Jain, K. Li and J. Lukens Summary: Using an in-situ, self-aligned deposition scheme, arrays of variable length SNS junctions in the range of 0.05/spl mu/m to 1 /spl mu/m have been fabricated. Arrays of SNS microbridges of lead-copper and niobium-copper fabricated using this technique have been used to study the length dependence, at constant temperature, of the critical current I/sub c/and bridge resistance R/sub d/. For bridges with lengths L greater than the normal metal coherence length /spl xi/sub n/(T), the dependence of I/sub c/on L is consistent with an exponential dependence on the reduced length /spl ell/=L//spl xi//sub n/(T). For shorter bridges, deviations from this behavior is seen. It was also found that the bridge resistance R/sub d/does not vary linearly with the geometric bridge length but appears to approach a finite value as L /spl rarr/ 0.         On Nb/sub 2/O/sub 5/growth and tunneling through Nb/sub 2/O/sub 5/    J. Halbritter Summary: Nb-Nb/sub 2/O/sub 2/interfaces are not only well known for deteriorated superconductivity but also for contradictory results on barrier height\bar{\phi}sampled by tunneling electrons. According to the Cabrera-Mott theory tunneling electrons define the oxide growth and thus oxidation and tunneling are linked. The oxidation of Nb is dominated by the growth of Nb/sub 2/O/sub 2/microcristallites and by oxygen diffusion. Both effects heavily strain the Nb-Nb/sub 2/O/sub 2/interface creating defects in Nb into which O is injected. This causes defects in Nb/sub 2/O/sub 2/as counterpart. These defect system weaken locally the superconductivity of Nb and the insulating properties of Nb/sub 2/O/sub 2/yielding so a serrated and eroded transition superconductor - insulator. In Nb/sub 3/Sn-, NbC-, NbN-, ... oxidation the defect creation in the metal is reduced yielding so thinner and less defective Nb/sub 2/O/sub 2/than in Nb oxidation. Tunnel measurements allow quantitatively the following classification: -NbO/sub 6/octahedra blocks (/spl ges/1 nm) with /spl phi/ /spl cong/ 1eV, with -channels with /spl phi/* /spl ap/0.1 eV in between and with -localized electron states n/spl ell/ E/sub F/ /spl ap/10/sup 15/ - 10/sup 20//cm/sup 3/eV as extended and localized defects. For Nb oxidation the channels are linked to NbO/sub x/lumps (T/sub c/ /spl ap/ = 0K) at the Nb surface. These defects yield the tunnel channels and the tunnel anomalies encountered in Nb/sub 2/O/sub 2/dominating below 50 meV the tunnel current.         Superconducting junction with resonant tunneling    V. Kresin and J. Halbritter Summary: In oxide coating metals, localized states exist, which strongly hybridize with conduction electrons forming interface states (IS). This hybridization yields several qualitative and Quantitative new effects typical for oxide coated metals. The Hamiltonians for these new effects describe the: - enhanced coupling of IS to phonons, - strengthened and weakened superconducting interaction of IS, - additional - resonant - tunnel channels via IS.         Nb metallurgical transformations occurring in the microbridge area of an rf SQUID during its critical current adjustment    Y. Monfort, D. Bloyet, J. Villegier and D. Duret Summary: We describe the metallurgical transformations of Nb thin-film Dayem microbridges related to the adjustment of their critical current at operating temperature (4.2 K). The critical current is reduced to a few tens of microamperes when the microbridge is submitted to proper current pulses. Subsequent Transmission Electron Microscopy (TEM) observations show an increase of the mean Nb grain size in the microbridge area. Nb contamination by the silicon substrate is also observed, Both critical temperature and critical current decreases are attributed to these pnenomena.         Hydrogenated amorphous silicon barriers for niobium-niobium Josephson junctions    H. Kroger, L. Smith, D. Jillie, J. Thaxter, R. Aucoin, L. Currier, C. Potter, D. Shaw and P. Willis Summary: We report on further studies of the effects of hydrogenation of sputtered amorphous silicon barriers upon the current-voltage (I-Y) characteristics of Nb-Nb Josephson tunnel junctions. For composite trilayer barriers (a-Si/a-Si:H/a-Si) which are deposited using 8 mT of Ar, we find that there is an abrupt improvement in device chararteristics when the central hydrogenated layer is deposited using a hydrogen partial pressure which exceeds about 0.5 mT. We attribute this to the reduction in the density of localized states in the a-Si:H layer. We have observed excellent I-Y characterisitics with trilayer barrier devices whose central hydrogenated layer is only about 1/7 of the thickness of the entire barrier. This observation suggests that localized states near the geometric center of the barrier are the most significant in degrading device characteristics. Annealing experiments and published data on the diffusion of deuterium in a-Si suggest that the composite barriers will be extremely stable during processing and storage. Zero bias anomalies in device I-Y characteristics and spin density in the a-Si and a-Si:H layers have been measured. Suggestions for future experiments are made.         Simplified fabrication of magnetically coupled Josephson circuits    L. Smith, D. Jillie and H. Kroger Summary: We describe a technique for fabricating magnetically coupled Josephson logic and memory circuits and SQUIDs which uses only two superconducting layers. These two layers perform multiple functions as the base and counterelectrodes of the tunnel junctions, the SQUID inductance and control lines, and the signal lines and groundplane between gates. This technique is illustrated by the specific example of a two junction, resistively damped SQUID designed to be fabricated using an all-refractory process which employs a total of five masking levels.         Preparation and properties of V/sub 3/Si thin films for superconducting electronics    S. De Stefano, A. Di Chiara, G. Peluso, L. Maritato, A. Saggese and R. Vaglio Summary: High quality V/sub 3/Si thin films have been prepared for applications in superconducting electronics, by means of a very simple and reilable technique. Structural properties, superconducting critical temperature and resistivity data are reported together with preliminary tunneling results.         Single-fluxoid quantum four-junction-interferometer operated in the phase mode    G. Oya, M. Yamashita and Y. Sawada Summary: We have theoratically and experimentally investigated the possibility of the phase mode operation of symmetrical four-junction Josephson interferometers (4J-loop), which are considered to play a key role as quantum logic devices for a Josephson switching system utilizing single-quanta as information bits, because of their excellent characters such as the kinetic momentum quantum effect and variety of the logic operations. The threshold characteristic, which is the most basic for Josephson interferometers to be operated in the phase mode and shows their fluxoid-quantum states, has experimentally been observed clearly for the first time for symmetrical 4J-loop's by using a novel radial-scanning, intensity-modulation technique, as predicted theoretically. It is characterized by a limited closed-shaped pattern. The number of the fluxoid-quantum states increases with LI/sub 0/for the loops. Two different basic types of switching behaviors, a vortex-to-vortex and a vortex-to-voltage transition, have been confirmed, which have clearly been separated on the threshold characteristic, for the loops with LI/sub 0/larger than /spl sim/0.7/spl Phi//sub 0/ The optimum LI/sub 0/value for the phase mode operation of the loops has been found to be 0.75/spl Phi//sub 0/ /spl lsim/ LI/sub 0/ /spl lsim/ 1.25/spl Phi//sub 0/. The desired performance of the phase mode operation of symmetrical 4J-loop has been confirmed by the shift motion of single fluxoids on the basis of the vortex-to-vortex transition of the loop. Finally, an application of such phase mode Josephson interferometers for pulse generators of Josephson sampling systems has been proposed.         Analysis of flux input and output Josephson pair device    K. Loe and E. Goto Summary: A new Josephson junction logic device working on the principle of parametron and operated entirely on dc flux for input, output and excitation is discussed in this article. Computer simulation of the device operation with clock signal of 100psec shows that the device is behaving very well as a logic element with very low power dissipation. The device's parameters and noise problems such as thermal noise and quantum tunnelling noise are also discussed. Promising results are obtained from the analysis.         Effect of bias electrodes on characteristics of long Josephson junctions    M. Radparvar and J. Nordman Summary: We have investigated the characteristics of long Josephson junctions with geometries containing several entry points for current. A single device can be biased at a junction end, at the center, or at both ends depending on the choice of electrodes. A branch of the current-voltage curves and the dependence of maximum DC Josephson current on an external magnetic field may be symmetric or asymmetric for a single device depending on the current feed points. In all of the cases, at a given current bias on this branch, the junction voltage increases with the application of an external magnetic field beyond a critical field. This is the minimum magnetic field necessary to introduce fluxons into the junction. A Simple model for tunnel current distribution is used to explain the experimental data. For an asymmetrically biased junction, we show that the effective dynamic resistance exhibited for bias at a boundary is either 0 or /spl radic/ l/c. This suggests that the dynamic resistance of the device may be varied by merely moving the bias feed point along the junction.         Impedance matching of an rf SQUID to a standard transmission line    D. Robbes, C. Dubuc, J. Lepaisant, D. Bloyet and D. Duret Summary: The rf SQUID resolution is known to be dependent on the pump frequency. For the vhf range and above, the classical rf high impedance circuit is not directly applicable and a "matched" configuration is necessary requiring suitable transmission line. We present a theoretical study of the SQUID matched to a standard fifty Ohms line and five optimization rules for obtaining the best resolution. The noise has been introduced first as a narrow-band source coming from the preamplifier and secondly completed by broad band contribution. Both theoretical and experimental results are presented demonstrating the usefulness of the model.         Quasiparticle mixing close to the gap frequency in aluminum tunnel junctions    D. Winkler, T. Claeson and S. Rudner Summary: We have tested the conversion efficiency of quasi-particle mixers at frequencies close to the superconducting gap frequency. We investigated arrays of aluminum SIS and SIN tunnel junctions at frequencies around 75 GHz and temperatures down to 0.3 K. This frequency corresponds to about 80% of the gap frequency. The experimental conversion loss was large due to severe impedance mismatches. However, we obtained a good agreement (within 1 dB) to the quantum theory of mixing, indicating that nonequilibrium effects do not play a significant role for these low current density junctions.         Effects of junction geometry on performance of flux-flow type Josephson oscillator    K. Yoshida, T. Nagatsuma, K. Sueoka, K. Enpuku and F. Irie Summary: Theoretical and experimental studies have been made of the effects of junction geometry on the performance of the flux-flow type Josephson oscillator. It is shown theoretically that the height and the slope of the current steps appearing in dc I-V curves of the junction, which determine the available power and the radiation linewidth of the oscillator, respectively, are dependent strongly upon self fields in the junction. In order to study the effects of junction geometries on the self fields, computer simulation and experiments have been carries out for an in-line junction, an overlap junction and an overlap junction with a small projection on one side. The best performance is obtained for the overlap junction with a moderate projection on side as expected theoretically.         Millimetre wavelength detection using Nb/NbO/sub x//Pb alloy tunnel junctions    N. Naclerio, J. Lumley, J. Evetts and R. Somekh Summary: Quasiparticle mixers have shown promise as millimetre and submillimetre wavelength detectors and mixers, with the potential for conversion gain and photon noise limited performance. We report on small area (0.1/spl mu/m/sup 2/- 1.0/spl mu/m/sup 2/) superconducting thin film edge junctions fabricated using a combination of magnetron sputter deposition and broad beam ion source technology for materials deposition, barrier formation, and electrode patterning. Devices fabricated on 0.1 /spl times/ 0.4 /spl times/ 4mm/sup 3/quartz substrates with a wide range of normal state resistances,20 < R/sub n/ < 1000 /spl Omega/ and critical current densities, 10/sup 2/ < j/sub c/ < 3 /spl times/ 10/sup 5/Acm/sup -2/, show steps due to photon assisted tunnelling with very small amounts of local oscillator power applied (10/sup -8/W). We have investigated a series of devices with various electrical characteristics and geometries all of which include integral superconducting choke structures. Results are presented and are compared with theoretical predictions.         Submillimeter wave response of tunnel junctions with an insulating barrier containing magnetic impurities    S. Imai, S. Morita, A. Ishikawa, Y. Takeuti and N. Mikoshiba Summary: We have investigated PAT (Photon-Assisted-Tunneling) effect induced by SMMW (Submillimeter-Wave) in SIS point-contacts with an insulating barrier containing magnetic impurities: a magnetic barrier. The junctions turned out to have severely suppressed dc and ac Josephson currents, which makes them promising junctions for a high frequency mixer using PAT effect.         Time domain simulation of Shapiro steps in Josephson junctions    S. Imai, S. Morita, M. Shinagawa, Y. Takeuti and N. Mikoshiba Summary: Using the time domain formulation of the theory of the tunnel junction, we investigated Shapiro steps by digital simulation, under the condition of a constant current source given by I/sub dc/ + I/sub rf/ sin /spl omega /t. The integral kernels for the Josephson and the quasiparticle current were computed assuming a nonzero pair breaking parameter /spl delta/=0., and T = 0K. We obtained I/sub rf/dependence of the zeroth and first Shapiro steps, I/sub 0/and I/sub 1/, and the frequency dependence of I/sub 1/ /sup MAX/, the maximum of the first Shapiro step as a function of I/sub rf/, for a few values of the junction capacitance. we found the following results. (1)I/sub 1/ /sup MAX//I/sub c/ (I/sub c/:the critical current), showed the Riedel peak at /spl omega///spl omega//sub g/ /spl sime/1, where /spl omega//sub g/is the gap frequency 4 /spl utri//h. (2) For /spl omega///spl omega//sub g/ >1 /spl middot I/sub 1//sup MAX//I/sub c/ agrees well with that for the constant voltage bias. (3) As the frequency becomes smaller below /spl omega/sub g/ //spl middot/ I/sub 1//sup MAX//I/sub c/ is severely depressed compared to that for the constant voltage bias.         A wideband device for measurement of the magnetic properties of materials    L. Avdeev, O. Snigirev and V. Khanin Summary: We have designed and tested the first version of the wideband SQUID-based universal instrument intended to study magnetic properties of matter within the frequency range 0-1 KHz, in the magnetic fields up to 0.15 T and the temperature range 4.2 - 330 K with the available sample volume /spl sim/ 0.5 cm/sup 3/. In the present device the spectral density of noise reduced to magnetic moment of the sample was close to 10/sup -10/Axm/sup 2//Hz/sup 1/2/at frequencies higher than 1 Hz, for the applied field 0.05 T and sample temperature 170 K. An analysis of the noise spectra for various applied magnetic fields has enabled us to indicate a probable main source of this noise and to outline ways to reduce the total noise, hopefully to the SQUID-determined values.         Superconducting current injection transistor with very high critical-current-density edge-junctions    B. Van Zeghbroeck Summary: A Superconducting Current Injection Transistor (Super-CIT) was fabricated with very high critical current-density edge-junctions. The junctions have a niobium base electrode and a lead-alloy counter electrode. The length of the junctions is 30/spl mu/m and the critical-current density is 190KA/cm/sup 2/. The Super-CIT has a current gain of 2, a large signal transresistance of 100mV/A and the turn-on delay, inferred from the junction resonance, is 7ps. The power dissipation is 3.5/spl mu/W and the power-delay product is 24.5aJ. Gap reduction due to heating was observed, limiting the maximum power dissipation per unit length to 1.1 /spl mu/W//spl mu/m. Compared to lead-alloy Super-CITs the device is five times smaller, three times faster and has a three times larger output voltage. The damping resistor and the contact junction could also be eliminated.         Superconducting granular NbN bolometer for ultrafast spectroscopy    S. Wolf, U. Strom, J. Culbertson and D. Paget Summary: A superconducting ultra thin granular NbN bolometer has been developed for the ultrafast detection of phonons and photons over a wide spectral range. This bolometer consists of an rf reactively sputtered film of NbN anodized to a final thickness of 30A. It operated over a wide temperature range (<1.4 to 14 K) has ultrafast response (<0.1 nanoseconds) and has demonstrated sensitivity to phonons in insulators, glasses and semiconductors, to microwaves and to infrared and optical photons. The response is nearly uniform over its temperature range and is linear with absorbed power.         Microwave application of three-terminal Josephson device under hot quasiparticle injection    T. Kobayashi, Y. Miura, M. Tonouchi and K. Fujisawa Summary: New effects of quasiparticle injection on microwave irradiated Josephson triodes are demonstrated. The device comprises Pb-insulator (Nb/sub 2/O/sub 2/)-Nb SIS junction with direct contact of the Nb film to n+-GaAs gate substrate. In this device, the very thin Nb film (300 - 600 /spl Aring/) as a base electrode of the SIS detector also serves as an acceptor of the quasiparticles injected from GaAs - Nb Sehottky barrier. The emphasis was placed on injections of hot quasiparticles with the energy in excess of 0.5 eV. The zeroth step height of microwave (10 GHz) irradiated Josephson current I/sub o/was efficiently modulated by a sufficiently low density quasiparticle injection current I/sub inj/(1 - 2 A/cm/sup 2/), though no sign of change was found in the superconductive gap parameter and the Josephson critical current itself. These characteristic features became less pronounced as the energy of injected quasiparticles was lowered below 50 meV. Though the present experiment is in a preliminary stage, a current amplification (dI/sub o//dI/sub inj/) of higher than two has been attained on a test specimen.         Proposed three-terminal superconducting device based on the magnetoelectric effect    A. Goldman Summary: The development of three-terminal superconducting devices with transistor-like characteristics may be crucial for a number of applications of superconducting electronics. A three-terminal Josephson device which in principle could have gain, and which depends on the magnetoelectric effect is described. The magnetoelectric effect is a property of the antiferromagnetic phase of certain compounds. When an electric field is applied across a magnetoelectric material, a magnetization develops. If one Josephson junction of a two-junction, three-electrode sandwich contained a magnetoelectric barrier, a magnetic field would result if that junction were switched to the finite voltage state. This field, when coupled into the second junction, would cause it to switch from the zero-voltage to the finite voltage state. If the second junction had a larger critical current than the drive junction, then the three-terminal device would have gain.         Nano-meter bridge with epitaxially deposited NbN on MgO film    T. Yamashita, K. Hamasaki, Y. Kodaira and T. Komata Summary: Nano-meter(nm)-bridges with high-T/sub c/materials hold great technological interest because of their smaller capacitance and expected higher I/sub o/R/sub n/-product. They are promising especially for applications such as high speed logic and high frequency radiation detectors. Also they can operate over a wide temperature range and are stable against thermal cycles as are incorporating the refractory high-T/sub c/superconductors. One of the essential ingredient for high quality bridges is to have NbN films. Ultra-thin NbN films have been prepared by rf reactive-sputtering. NbN films deposited epitaxially on rf sputtered MgO films have high superconducting transition temperature T/sub c/. T/sub c/value of the film with thickness of about 5nm was about 14K, and is much higher than those deposited on Al/sub 2/O/sub 3/films and Si substrates. Two types of nm-bridges were reproducibly fabricated with NbN films deposited epitaxially on MgO films. The obtained I/sub o/R/sub n/-products were in a range of 0.5 to 3.6mV. The microwave-induced voltage steps were observed up to the voltage comparable to I/sub o/R/sub n/- product. The dc and ac quantum effects of the dc SQUIDs were observed in quite wide range of temperature, 4.2 to 11.4K.         Phase-quantum tunnel device    M. Sugahara, M. Nagai, N. Yoshikawa, N. Ando, Y. Ogawa and H. Kaneda Summary: Theoretical and Experimental study on granular superconductors shows that (i) they are classified into two groups; fixed-phase superconductor (/spl theta/-superconductor) and fixed-pair-number superconductor (N-superconductor), and that (ii) a new macroscopic quantum device with conjugate property to Josephson effect can be made by use of N-superconductors.         Quantum noise in SIS mixers    A. Zorin Summary: A quantum-statistical analysis of the signal and noise performance of the quasiparticle (SIS) heterodyne mixers is presented. In contrast with the earlier theories, the quantum properties of the signal source have been taken into consistent consideration. In the quantum range of sensitivity the noise properties of the mixer can be characterized by the noise parameter /spl theta//sub n/introduced earlier for the parametric amplifiers. Using the conventional 3-port model of the mixer circuit and the microscopic theory of the superconducting tunnel junctions we have obtained a general expression for /spl theta//sub n/and evaluated it numerically for various quasiparticle current step widths, dc bias voltages, local oscillator powers, signal frequencies /spl omega//sub s/, signal source admittances Y/sub s/and operation temperatures T. In a reasonable range of these parameters,/spl Theta//sub N//sup DSB/ has turned out to be less than the so-called quantum limit h/spl omega//sub s//2. On the contrary, in the single sideband mode of the mixer performance, /spl theta//sub n/is always larger than h/spl omega//sub s//2. The difference between the two modes of operation is discussed from the point of view of the quantum theory of measurements.         Bloch oscillations in small Josephson junctions: Possible fundamental standard of dc current and other applications    K. Likharev and A. Zorin Summary: Possible applications of the quantum "Bloch" oscillations of the frequencyf_{B} = (\bar{I}-\bar{V}/R)/2ein Josephson junctions with very small capacitance C (e/sup 2//2C<< k/sub B/T) are discussed. The most natural application of this effect could be a fundamental standard of the dc current: I= 2efm, where f is an external radiation frequency and m is an integer. Of the other applications, a possibility to develop a sub-picowatt superconducting transistor seems the most attractive. Analog properties of the small junctions and prospects of their use in microwave receivers are also discussed briefly. Conditions of experimental observation and practical applications of the Bloch oscillations are formulated and the main apparent problems are outlined.         Reversible conveyer computation in array of parametric quantrons    K. Likharev, S. Rylov and V. Semenov Summary: A possibility of physically and logically reversible processing of digital information in Josephson-junction circuits of a reasonable complexity has been considered. As example, a 8-bit 1024-point fast convolver has been designed on the basis of a two-dimentional quasi-uniform array of /spl sim/250 /spl times/ 30,000 parametric quantrons. This completely reversible conveyer device can operate with the estimated rate of at least spl sim/10/sup 9 numbers per second, which corresponds to spl sim/10/sup 14/ binary logical operations per second. At this rate the power dissipation in the whole device can still be as low as /spl sim/30nW. A new mode of the parametric quantron operation with larger parameter margins is also described.         Ultra-short weak links of superconductors    H. Ohta and Y. Yamada Summary: Nananeter long weak links of quasi-planar geometrical structure have been made only of niobium. The critical current of an two-junction interferometer of the nan-ter-long quasi-planar Josephson junctions (QPJJ) has been changed by a magnetic field to be one quarter of the zero-field critical current. This is important for applications of weak links to both DC SQUID and logic circuits. Microwave responce of QPJJ'S were excellent at 10,24,and 110 QHz.Change in the critical current of 10 /spl mu/A was less than 10 % after 50 times temperature cycles between liquid helium temperature and room temperature. QPJJ's are very reproducibly fabricated by lithographic techniques even though surface of niobium thin films is very active chemically. It would be safe now to say that we have obtained a mechanically stable substitute for a point contact Josephson junction of niobium.         Fabrication of niobium-lead tunnel junctions using a self aligned masking technique    A. Jain, J. Sauvageau, D. Schwartz, K. Springer and J. Lukens Summary: The use of suspended stencils in the self aligned fabrication of niobium lead tunnel junctions has been investigated. It is shown that while all-polymer masks are unsatisfactory for this application, suspended aluminum stencils supported on polyimide can be used to make these junctions with good current-voltage characteristics. This stencil, which can be baked to at least 200/spl deg/C, is made using e-beam lithography, lift off and plasma etching in oxygen. With this technique, junctions with submicron dimensions have been fabricated in a single masking step without any surface cleaning of the niobium film. The current-voltage characteristic of these junctions do not show the knee structure which is generally attributed to a contamination or damaged layer on the niobium surface.         Switching speed of DCL-gates with high-J/sub c/Josephson junctions    T. Nishino, Y. Tarutani, Y. Hatano and U. Kawabe Summary: Switching speed and bias current margin of DCL-gates composed of high-J/sub c/junctions are investigated by both numerical calculation and experimental measurement. It is shown that switching speed is improved by increasing J/sub c/. However, the switching speed and bias current margin of DCL-gates are restricted by the increase in the minimum resetting current for the high-J/sub c/junction. The theoretical J/sub c/limit for a Nb oxide barrier junction is found to be about 7x10/sup 8/A/m/sup 2/from numerical results, and the J/sub c/values that produce bias current margins of greater than 20 % are found by both numerical and experimental results to be less than 2 /spl sim/ 3 /spl times/ 10/sup 8/A/m/sup 2/. The switching delay obtained experimentally for a DCL-gate with a J/sub c/value of 2 /spl times/ 10/sup 8/A/m/sup 2/is 5.6 ps, which is in good agreement with the numerical result.         Fabrication and testing of the 3-m diameter superconducting solenoid and refrigeration system for the Fermilab Collider Detector    R. Fast, R. Dachniwskyj, R. Kephart, M. Stone, R. Wands, K. Kondo, H. Minemura, S. Mori, R. Yoshizaki, K. Aihara, K. Asano, I. Kamishita, I. Kurita, R. Saito and T. Suzuki Summary: A large, 1.5-T conduction cooled superconducting solenoid for the Collider Detector at Fermilab was designed and built as part of a US-Japan international high-energy physics collaboration. Initial tests of the coil without its iron return yoke indicated that the coil performed as designed and should operate in a very stable manner when installed in the flux return iron at Fermilab. The refrigeration system for the solenoid has been installed and operated with a dummy load. The nominal 600-W capacity of the system was achieved in the initial test.         A Nb/sub 3/Sn dipole magnet reacted after winding    C. Taylor, R. Scanlan, C. Peters, R. Wolgast and W. Gilbert Summary: A 5 cm bore dia., 1-m-long dipole model magnet was constructed by winding un-reacted cable, followed by reaction and epoxy-impregnation. Experience and test results are described on the 1.7 mm dia. internal-tin wire, the eleven-strand flattened cable, fiberglass insulation, and construction of the magnet. Each half of the magnet has two double-pancake-type windings that were reacted in a single operation. The two double-pancakes were then separately vacuum impregnated after soldering the flexible Nb-Ti leads to the Nb/sub 3/Sn conductors. No iron flux return yoke was used. In initial tests a central field of 8.0 T was reached at 4.4 K. However, evidence from training behavior, and 1.8 K tests indicate that premature quenching, rather than critical current of the cable, limited the field intensity. The magnet was reassembled and more rigidly clamped; additional test results are reported.         A 40 mm bore Nb-Ti model dipole magnet    C. Taylor, W. Gilbert, W. Hassenzahl, R. Meuser, C. Peters, J. Rechen and R. Scanlan Summary: Preliminary R and O has been started on magnets for a next-generation high-energy-physics accelerator, the 20 TeV Superconducting Supercollider (SSC). One design now being developed at LBL is described in this paper. The design is based on two layers of flattened Nb-Ti cable, a 40 mm I.D. winding with flared ends, and an operating field of 6.5 T. Experimental results are presented on several one-meter-long models tested at both He I and He II temperature. Measurement of field, residual magnetization, quench propagation velocity, and winding prestress are presented. (A 2-in-1 magnet based on this coil design is being Jointly developed by LBL and Brookhaven National Laboratory, and 15 ft. long models are being constructed at BNL).         I/sub c/(H,T) measurements for multi-kiloampere superconducting magnet conductor    A. McInturff, R. Lundy, R. Remsbottom and M. Wake Summary: Measurements of the transition current as a function of both applied magnetic field and temperature are presented as an equivalent resistivity for various production and prototype magnet conductors. The current range is from a few amperes to 14.0 kiloamperes from '0' T to 10.0 T applied field. The range in temperature was 1.7K to 4.6K. The statistical average of the over 900 Tevatron magnet cable samples was 5.107 amperes for an effective resistivity of 2/spl times/10/sup -12/ /spl Omega/-cm at 5T and 4.2K. Data are presented for the new 10kA, 10T "Rutherford Style Cable" and for the temperature range of 1.7 to 4.3K for NbTi and NbTiTa, and the 6.0T, 7kA, 4.4K conductor for the "SSC" models, "Superconducting Super Collider"         Persistent current fields in Fermilab Tevatron magnets    B. Brown, H. Fisk and R. Hanft Summary: Data on the persistent current residual fields in Tevatron dipoles and quadrupoles are presented. The data are compared to the doublet theory of persistent current fields and an estimate is given for the multipole fields expected in the Superconducting Super Collider (SSC) dipole proposed by Fermilab.         Warm yoke dipole prototypes for HERA    G. Horlitz, H. Kaiser, G. Knust, H. Lierl, K.-H. Mess, S. Wolff, P. Schmuser and B. Wiik Summary: A superconducting dipole magnet with warm iron yoke has been developed for the proton storage ring of HERA. The nominal field is 4.53 T and the magnetic length is 6.08 m. Ten dipole coils and three complete magnets have been built. Tests at liquid helium temperature have been performed with two coils and one complete magnet. The dipoles exhibit very little training and have excellent field quality.         Superconducting Super Collider 5T dipole magnet cryogenic design    R. Niemann, J. Carson, H. Edwards, N. Engler, J. Gonczy, R. Hanft, R. Lundy, P. Mantsch, A. McInturff, T. Nicol, R. Powers, R. Remsbottom, C. Rode, E. Schmidt and A. Szymulanski Summary: Proposed colliding beam particle accelerators for high energy physics research will employ superconducting accelerator rings. The rings' superconducting magnet systems must provide the required magnetic function, have low refrigeration load, operate with very high reliability and be manufacturable at a low cost. The cryogenic aspects of a conceptual design for a 5T field, 5cm aperture, 12m long superconducting dipole magnet suitable for a 20 TeV proton-proton collider are presented.         A 1.6 GeV/c superconducting switching magnet    J. DeKamp, M. Dubois, J. Nolen, R. Swanson and A. Zeller Summary: A superconducting switching magnet capable of bending a 1.6 GeV/c beam to /spl plusmn/16/spl deg/has been designed and is currently under construction. In the operating range of up to 1.75 T the design field uniformity is better than 0.1% in the volume occupied by the beam. The coils are wet wound with a filled epoxy and are designed to have an average current density of 17 kA/cm/sup 2/when operated at the nominal maximum current of 100 A. In order to keep the liquid helium consumption low, consistent with a weekly batch-fill operation, the magnet will operate in persistant mode with small resistive coil correction magnets to provide for fine tuning of the beam.         Distribution of shielding currents in a cylindrical superconducting tube    Z. Feng Summary: Superconductive cylindrical tubes can be used to shield out magnetic flux for high energy physics use. The shielding currents in the tube are found based on a physical model. The model is based on the principle that the flux linked by a superconducting loop must be conserved. For a finite cylindrical superconducting tube, the axial distribution of shielding currents for a given shielded magnetic field is determined, which agrees with experiment. Some facts are found, that is, first, the external shielded magnetic field can partly penetrate into the bore at the two ends of a finite superconducting tube where I/sub c/is first reached; second, the shielding currents in the end region are about the same for different aspect ratio /spl beta= /spl ell//Rtubes; third, if the radii of the tube are properly reduced from the middle to the ends then the shielding currents can become uniformly distributed. These analytic results agree generally with experiment.         SQUID based beam current meter    M. Kuchnir, J. McCarthy and P. Rapidis Summary: The concept of a current meter for DC beams based on commercially available SQUIDs has been implemented and tested in a series of prototypes. One of them is expected to be used for monitoring the beam of our Antiproton Accumulator. After a brief explanation of the principles of operation, pick-up-loop design, magnetic and RF shielding considerations these prototypes and the experience acquired with them is described.         Performance of superconducting storage ring cavities at 1500 MHz    P. Kneisel, J. Amato, J. Kirchgessner, K. Nakajima, H. Padamsee, H. Phillips, C. Reece, R. Sundelin and M. Tigner Summary: Application of superconducting cavities in high energy storage rings offers the advantage of considerable power savings over normal conducting structures. The fabrication, processing and performance of three five-cell, elliptically shaped 1500 MHz storage ring cavities, which have been built from reactor grade niobium and which are equipped with fundamental mode power couplers and higher order mode couplers, are described. Q-values of 5x10/sup 9/at 2.1/spl deg/K and accelerating gradients of 9 MV/m have been achieved using commercial grade niobium. The use of higher thermal conductivity niobium offers the possibility of thermally stabilizing the material and increasing the tolerable power dissipation. With niobium of three times the thermal conductivity of reactor grade material accelerating gradients up to E/sub acc/= 15.3 MV/m corresponding to peak magnetic surface fields of 71.6 mT have been achieved.         Reduction of surface resistance in superconducting thin films by microwave irradiation    J. Amato Summary: We have experimentally observed dramatic reductions in the microwave surface resistance R/sub s/of superconducting aluminum thin films due to microwave pumping. For temperatures T > 0.97 T/sub c/, nearly complete suppression of the temperature-dependent component of R/sub s/occurred when the films were subjected to a microwave magnetic field < 1 Oe at 11.4 GHz. Contrary to theoretical predictions, several abrupt transitions to superconducting states with lower R/sub s/were observed before the transition to the normal state. The reduction of R/sub s/may provide stability against thermal breakdown in rf cavities currently limited by defect-nucleated quench.         A new purification technique for improving the thermal conductivity of superconducting Nb microwave cavities    H. Padamsee Summary: Improvement factors up to 4 in the thermal conductivity of Niobium between 4 and 9K are obtainted by a new purification technique which removes the dominant interstitial impurity (oxygen) found in commercial Nb. In the process, surfaces of the cavity are brought into proximity with Yttrium foil at -10/sup -5/torr for several hours. A vapor deposited film of several /spl mu/m thickness traps oxygen diffusing rapidly from the bulk to the surface. A single cell, 1500 MHz, elliptically shaped cavity with thermal conductivity improved by this method shows amelioration of thermal breakdown, as predicted by thermal model calculations.         Effect of oxide layer on microwave surface resistance of superconducting niobium    F. Palmer and M. Tigner Summary: We have measured the influence of oxide layers on the surface resistance of niobium resonant cavities at temperatures below 1.4/spl deg/K. The 8.6 GHz cavity halves were drawn from high purity rolled sheet and electron beam welded together. We measured the resonance quality, Q, of several cavities after alternately removing and growing an oxide layer on the inside surface. Removal was accomplished by absorbing the oxygen into the bulk Nb, at 1100-1200/spl deg/C, the required temperature having been determined by Auger spectroscopy. Oxide layers were grown by admitting pure oxygen into the cavity at reduced pressure. We found that these oxide layers contribute a residual resistance of /spl sim/10/sup -8//spl Omega/.         Superconducting niobium cavities of improved thermal conductivity    H. Lengeler, W. Weingarten, G. Muller and H. Piel Summary: The construction of large scale superconducting accelerators asks for reliable and economical manufacturing procedures for the superconducting cavities. The improvement of thermal conductivity of the niobium used can be of great benefit in that respect. We have built and tested single cell cavities at 500 MHz and 3 GHz from a newly available niobium sheet material of improved thermal conductivity. At 500 MHz a maximum accelerating field of 13.0 MV/m at 4.2 K was achieved. At 3 GHz and 1.5 K as a best result 18.7 MV/m were obtained. A total of 15 cavity tests were carried out and the results clearly exceed field values obtained so far with standard reactor grade niobium at CERN and Wuppertal. Measurements of the thermal conductivity of niobium at helium temperatures are discussed, the temperature dependence of the surface resistance of high purity niobium is given, the observed field and Q limitations and electron loading phenomena are outlined.         Test results from two 5m two-in-one superconducting magnets for the SSC    J. Cottingham, P. Dahl, R. Fernow, M. Garber, A. Ghosh, C. Goodzeit, A. Greene, J. Herrera, S. Kahn and E. Kelly Summary: Two 5m long superconducting dipole magnets with specifications similar to the reference design for the proposed Superconducting Super Collider have been successfully tested. The "cos /spl theta/" coils of the magnets were made from two layers of "standard" CBA/Tevatron NbTi superconductor, keystoned to an angle of 2.8 degrees. The inner diameter of the inner layer was 3.2 cm. The ends of the coils were flared to increase the minimum bending radius so that future magnets can be wound from prereacted Nb/sub 3/Sn. The windings of the two-aperture magnets were clamped in a "two-in-one" iron yoke with a tensioned stainless steel shell. The fields of the two apertures were closely coupled, since the flux in one aperture returned through the other. The inner and outer layers of the coil were powered separately so that their short-sample limits would be reached simultaneously. With minimal training the magnets reached a central field of 6 T, the short sample limit of the conductor at the 4.5 K temperature of the liquid helium bath. At 2.6 K, a central field in excess of 7 T was reached, again with minimal training. The measured values of the allowed sextupole and decapole harmonics are within 10% of the calculated values and the non-allowed harmonics are all small or zero, as predicted.         Low noise microwave parametric amplifier    A. Smith, R. Sandell, J. Burch and A. Silver Summary: We report the lowest noise temperature of any microwave amplifier except the maser. This amplifier is a nearly degenerate superconducting parametric amplifier at X-band consisting of a low /spl beta/, thin film, single junction SQUID, a monolithic 50 /spl Omega/ to 1 /spl Omega/ impedance matching network, and a cooled circulator. Nb/Nb/sub 2/O/sub 2//Pb alloy junctions were incorporated into Nb and Pb-in circuitry on 1X2 cm silicon chips. The SQUID was phase-biased near 90/spl deg/and driven by an external pump at approximately twice the operating frequency. The self-resonance frequency of the SQUID inductance and junction capacitance was set at the operating frequency of 8.2GHz. The operating charac teristics depended on the pump amplitude, the junction phase bias, and the SQUID parameters. For small values of /spl beta/ < 1, the maximum gain in both the signal and idler channels was /spl ap/10dB, the bandwidth = 170MHz, and the single-sidehand noise temperature was 6K with an uncertainty of (+15 to -7)K. For higher /spl beta/, the gain increased to nearly 30dB with increased noise and parametric oscillations occurring near the pump subharmonic frequency.         DC SQUID as a tuned radiofrequency amplifier    C. Hilbert and J. Clarke Summary: The design criteria for a tuned radiofrequency amplifier based on a dc SQUID are briefly discussed. A practical amplifier involving a planar dc SQUID with a 4-1/4-turn spiral input coil and operated at 4.2K had a gain of 18.6 /spl plusmn/ 0.5 dB and a noise temperature of 1.7/spl plusmn/ 0.5K at 93 MHz. These results are in satisfactory agreement with predicted values.         Practical DC SQUIDs with extremely low 1/f noise    C. Tesche, K. Brown, A. Callegari, M. Chen, J. Greiner, H. Jones, M. Ketchen, K. Kim, A. Kleinsasser, H. Notarys, G. Proto, R. Wang and T. Yogi Summary: A large number of highly robust and reliable thin film DC SQUIDs have been designed and fabricated which have excellent low frequency noise properties. Measurements performed on isolated devices have yielded a limit on the low frequency (1/f) flux noise component which is at least a factor of 60 below the average value reported for devices of this kind. The corresponding energy factor in the white noise region is 770 h at 0.1 Hz. The input coil inductance is 0.7 /spl mu/H and the coupling efficiency /spl alpha/ = 0.9. The substantial reduction of the low frequency noise in these SQUIDs demonstrates that improvements in the performance of these devices in the white noise region can be obtained without sacrificing the low frequency resolution.         DC SQUIDs with planar input coils    C. Pegrum, D. Hutson, G. Donaldson and A. Tugwell Summary: We describe the key parts of our recent work to develop a planar thin-film DC SQUID with a closely-coupled spiral input coil. Our aim has been to make a device that is superior to present RF SQUID sensors in terms of sensitivity and long-term reliability. To be compatible with an RF SQUID the inductance of the input coils must be relatively large, typically 2 /spl mu/H, and the input noise current in the white noise region should be below 10pA Hz/sup -1/2/. A low level of 1/f noise is also necessary for many applications and should be achieved without the use of complex noise-cancelling circuitry. Our devices meet these criteria. We include a description of work on window and edge junction fabrication using ion beam cleaning, thermal oxidation and RF plasma processing.         Fabrication and test of a forced cooled Nb/sub 3/Sn superconducting coil    K. Agatsuma, K. Kaiho, K. Komuro, Y. Ikeno, N. Sadakata, M. Sugimoto and O. Kohno Summary: The forced cooled Nb/sub 3/Sn superconducting magnet has been manufactured and tested in a high field test facility(HFTF). It consists of 4 double pancake coils by wind & react process. The magnet has been successfully tested under 4T of the back up field of HFTF this August. The test results appear that the quench of the magnet has occurred under the conditions of 8,000A, 6T and 10.3K. Those results have proved the good performances of the conductor and its magnet.         Minimum structure magnetic energy storage solenoids with a toroidal insert    M. Hilal, O. Arici and M. Cuban Summary: Force-free magnetic energy storage devices are not possible and a theoretical minimum structural mass is required as determined by the virial theorem. The support structure required for a given system depends on geometry as well as current distribution. This paper considers an arbitrary cross-section energy storage solenoid carrying a given poloidal surface current distribution. To reduce the mass of the required structure, a toroidal current is provided on the inner surface of the solenoid cross-section to partially overcome the radially outward magnetic forces generated by the poloidal current. A minimum mass energy storage solenoid is obtained by determining the optimum cross-section and the corresponding optimum surface current distribution. The structural mass obtained for the optimized solenoid is only a few percent greater than the structural mass required based on the virial theorem and thus is more efficient superconducting magnetic energy storage devices are possible.         Operation of 17.5 T superconducting magnet system in the last 8 years    K. Tachikawa, Y. Tanaka, K. Inoue, K. Itoh, T. Asano and Y. Iijima Summary: A 17.5 T hybrid superconducting magnet with an outer Nb/sub 3/Sn section and an inner V/sub 3/Ga section was installed at National Research Institute for Metals (Japan) at the beginning of 1976. Since then the magnet system has been successfully operated about 60 times without any trouble. The magnet still generates the world-highest field in the superconducting state. Ordinarily, it is cooled from room temperature down to about 15 K using two helium refrigerators with a total refrigeration power of 750 W at 20 K. For one day operation, about 120 liters of liquid is transfered into the cryostat. It requires about 2 hours to induce the magnetic field from 0 to 17.5 T. The liquid helium evaporation rate is about 4.5 liters/hr when the magnet is in full operation. To suppress the instability due to the tape movement, it was necessary to refasten tie-rods between the upper and lower flanges of the magnet during the first few years after the installation. The magnet has been effectively used to measure the critical current of newly developed high-field superconductors.         MIT 12 tesla test coil experiment    M. Hoenig and M. Steeves Summary: A 1 m diameter test coil consisting of three 39 m lengths of Internally Cooled Cabled Superconductor (ICCS), wound in the form of three double pancakes, has been installed in the 9 T background field High Field Test Facility (HFTF) at the Lawrence Livermore National Laboratory (LLNL). The ICCS conductor is a 486 strand bronze matrix Nb/sub 3/Sn cable, encapsulated in a squared-off JBK-75 tube with a 32% helium space. The paper describes major test coil characteristics, method of fabrication and test objectives. Tests will be performed during September-October 1984.         Magnet cooling economics    J. Parmer and M. Liggett Summary: The recommendation to use superfluid helium II in superconducting magnet design has become more prevalent in recent years. Advanced fusion reactor studies such as the Mirror Advanced Reactor Study recently completed by the Lawrence Livermore National Laboratory (LLNL) have based superconducting magnet design on the use of He II because of reduced magnet volume, improved stability characteristics, or increased superconductor critical current at fields above 9 Tesla. This paper reports the results of a study to determine the capital costs ($/watt) and the operating costs (watts/watt) of refrigeration systems in the 1.8K to 300K temperature range. The cost data is applied to a 1.8K magnet that is subject to neutronic heating wherein the magnet case is insulated from the winding so that the case can be cooled at a higher temperature (less costly) than the winding. The life cycle cost (capital plus operating) is reported as a function of coil temperature and insulation thickness. In some cases there is an optimum, least-cost thickness. In addition, the basic data can be used to evaluate the impact of neutron shielding effectiveness trades on the combined shield, magnet, cryorefrigerator, and operating life cycle cost.         Shorts due to diagnostic leads    J. Ellis, M. Lubell, S. Walstrom, P. Walstrom, R. Thome and R. Pillsbury Summary: The superconducting toroidal field coils that are being tested in the Large Coil Test Facility (LCTF) are heavily instrumented. In the General Electric coil, a lead wire of an internal sensor became shorted across an estimated three or four turns of the pancake winding. This short occurred during the final stages of the winding fabrication and was not accessible for repair. Resistance, voltage gradient, and transient voltage decay measurements were performed to characterize the short and the magnetic damping of the large steel bobbin and outer structural ring. The 32-gage wire causing the short was estimated to be about 10 cm long, with a resistance of 55 m/spl Omega/. As a safety measure, we decided to Burn out the shorted wire at room temperature before installing the coil in LCTF. Tests were made to determine the energy needed to vaporize a small wire. Computer calculations indicated that within the voltage limits set for the coil, it was not feasible to burn out the wire by rapidly dumping the coil from a low-current dc charge-up. We accomplished the burnout by applying 800 V at 3.25 A, and 60 Hz for about 1 s. Transient voltage decay measurements made after the burnout and compared with those made before the attempt confirmed that the short had indeed been opened.         Poloidal field coil and cryogenic systems for the TFCX tokamak    J. Schultz, D. Montgomery, R. Thome, E. Bobrov and R. Fleming Summary: The Tokamak Fusion Core Experiment (TFCX) is considering four design options, each of which has superconducting poloidal field (PF) coils. AThe use of a superconducting PF system is a feature of three of the four the conceptual design options. The high performance copper TF option has a partially superconducting PF system. The TFCX PF system will be unique in scale and performance. No operating tokamak or tokamak under construction has a superconducting PF system. A unique feature of the TFCX PF system will be the combination of moderately high pulsed field loads and neutron/gamma loads, due to the light neutron shielding required for a cost-effective next step tokamak reactor. The reference concept for the superconductor in the TFCX PF coils is an internally-cooled, cabled superconductor (ICCS), similar to that used in the Westinghouse LCP and the M.I.T. 12 T Coils, but probably using a more advanced superconductor and conduit design. Three different cooling topologies are being investigated: conventional cable in conduit, cable and tube in conduit, and internally-cabled, externally-cooled construction. For the all superconducting tokamak options, all coils are contained in a common dewar. For the options with copper toroidal field magnets, most of the coils are contained by an inner dewar, while the large bore ring coils have separate dewars and cooling systems. Pulsed and steady-state cryogenic heat loads must be removed from the poloidal field coils and vacuum system cryopumps. A conventional helium refrigerator/liquefier is combined with a separate cold circulator loop for the forced-flow magnet windings.         High-performance TF coil design for the Tokamak Fusion Core Experiment (TFCX)    V. Srivastava Summary: The Tokamak Fusion Core Experiment (TFCX) is a proposed concept for an ignited, long-pulse, current-driven tokamak device. Toroidal field (TF) coil winding cross section in the inboard region is impacted by peak field (10 T), winding current density (/spl sim/3500 A/cm/sup 2/), and peak nuclear heating rates (50 mW/cm/sup 3/). The winding utilizes a Nb/sub 3/Sn internally cooled cable superconductor (ICCS), which is a modified version of the conductor used in the Westinghouse Large Coil Program (LCP) coil. These modifications include the increase of void fraction from 32% to 41% of the cable space for withstanding higher nuclear heating rates and a thicker conduit wall to carry larger magnetic loads. The critical current of a Nb/sub 3/Sn conductor is strongly dependent on strain in the superconducting strands. The strain in strands is lower when the windings are wound and then reacted (W/R), as compared to reacted and then wound (R/W). The impact of these approaches on winding performance is discussed. The windings are pancake wound and cooled with supercritical helium. The liquid helium (LHe) inlet (/spl sim/4 K) and outlet (/spl sim/5.5 K) connections are located on the sides of the TF coils. The conductor design, the winding design, and performance analysis are described.         EBT-P Magnet Development Program summary    T. McManamy, J. Lue, J. Ballou, T. Mann, S. Shen and C. Wilson Summary: The ELMO Bumpy Torus Proof-of-Principle Magnet Development Program, which began in 1979, has fabricated and tested three NbTi superconducting magnets. The magnets are metastable with a maximum winding pack current density of 10,000 A/cm/sup 2/at a peak field of 7.4 T. Each magnet has been installed in a close-fitting dewar with a warm bore. Previous publications have reported successful tests of the first two windings in a large dewar, tests of the first complete magnet in its own dewar, and construction details of the dewars. This paper gives procedures and results for the test of the third winding in an open dewar, the test of the second single magnet in its own dewar, and two tests in which two magnets were run in series to generate a 73,000-lb side load at 5 T. The last tests verified the mechanical integrity of the design and qualified two of the magnets for use in the National Radio Frequency Test Facility.         Development of a large high-current-density Nb/sub 3/Sn superconductor made by solid-liquid diffusion method    M. Nagata, K. Ohkura, S. Isojima, M. Watanabe, M. Umeda and Y. Kimura Summary: A 3KA class multifilamentary Nb/sub 3/Sn superconductor has been developed by using solid-liquid diffusion method. The conductor has a very high critical current density of 1.0x10/sup 5/A/cm/sup 2/at 10 T excluding Cu. The conductor was fabricated in a large quantity and wound into a 40 cm bore Nb/sub 3/Sn magnet to prove its availability for a large high field magnet. The magnet attained to its designed operation point of 10 T with 2KA without quenching, when the currnet density in the magnet exceeded 74 A/mm/sup 2/.         Generalized multi-dimensional propagation velocity equations for pool-boiling superconducting windings    E. Christensen and J. O'Loughlin Summary: Several finite difference, finite element detailed analyses of propagation velocities in up to three dimensions in pool-boiling windings have been conducted for different electromagnetic and cryogenic environments, Likewise, a few full-scale simulated winding and magnet tests have measured propagation velocities. These velocity data have been correlated in terms of winding thermophysical parameters. This analysis expresses longitudinal and transverse propagation velocities in the form of power function regression equations for a wide variety of windings and electromagnetic and thermohydraulic environments. The generalized velocity equations are considered applicable to well-ventilated, monolithic conductor windings. These design equations are used piecewise in a gross finite difference mode as functions of field to predict the rate of normal zone growth during quench conditions. A further check of the validity of these predictions is available through total predicted quench durations correlated with actual quench durations of large magnets.         Computer simulation of multiple stability regions in an internally cooled superconducting conductor and of helium replenishment in a bath-cooled conductor    L. Turner and J. Shindler Summary: For upcoming fusion experiments and future fusion reactors, superconducting magnets have been chosen or considered which employ cooling by pool-boiling HeI, by HeII, and by internally flowing HeI. The choice of conductor and cooling method should be determined in part by the response of the magnet to sudden localized heat pulses of various magnitudes. The paper describes the successful computer simulation of multiple stability in internally cooled conductors, as observed experimentally, using the computer code SSICC. It also describes the modelling of helium replenishment in the cooling channels of a bath-cooled conductor, using the computer code TASS.         Fabrication and evaluation of a cryostable Nb/sub 3/Sn superconductor for the Mirror Fusion Test Facility (MFTF-B)    R. Scanlan, J. Zbasnik, R. Baldi, J. Pickering, Y. Furuto, M. Ikeda and S. Meguro Summary: The MFTF-B magnet system requires two 12.5T, 36 cm bore, insert coils. These coils are being constructed with a cryostable Nb/sub 3/Sn conductor manufactured by Furukawa Electric Co. The conductor consists of a core soldered into a cold-worked copper housing, which provides strength. The Nb/sub 3/Sn core is made by a triple extrusion bronze process. A total of 57 lengths, each 295 m long, have been made and tested. We have made extensive tests on this conductor; these tests include critical current, ambient and 4.2 K mechanical property measurements, critical current as a function of tensile strain, and bending tolerance tests. The critical current density was found to be quite anisotropic in this conductor, with J/sub c/(12T) = 650A/mm/sup 2/for field perpendicular to the conductor wide face, and J/sub c/(12T) = 500A/mm/sup 2/for field parallel to the conductor wide face. These values are among the highest reported for a production lot of Nb/sub 3/Sn conductor.         Comprehensive design procedure and spreadsheet for internally cooled cabled superconductors    P. Materna Summary: A comprehensive procedure has been set up to consider together the various phenomena influencing the design of an Internally Cooled Cabled Superconductor (ICCS). Sensitivity studies done for TFCX show the relative order of importance of conduit structural behavior assumption, dump circuit design, and nuclear heating rate on the cavity current density. Although none of these is completely specified or known presently, the TFCX TF coil design goal of 3500 A/cm/sup 2/at 10 Tesla appears achievable using moderately optimistic assumptions. The study was done in an automated manner using spreadsheet software on a personal computer, which proved to be extremely convenient and flexible.         Cryogenic system development and helium behavior study for forced-flow superconducting coils    T. Kato, E. Tada, Y. Takahashi, K. Okuno, H. Tsuji, T. Ando, T. Hiyama, K. Koizumi, H. Nakajima, O. Takahashi, K. Kawano, M. Oshikiri, M. Nishi, Y. Yoshida, Y. Hattori, R. Takahashi, S. Kamiya and S. Shimamoto Summary: In Japan Atomic Energy Research Institute (JAERI), cryogenic technology development is propelled to aim at realization of superconducting coil system for fusion experimental reactor (FER). For this purpose, forced-cooling technology which is one of attractive cooling methods and is expected to use for one of large superconducting coils for fusion is being investigated according to the cryogenic technology development program shown in Fig. 1. JAERI has already constructed and tested three forced-flow generating facilities which are named as forced flow generator (FFG), segment test facility (STF) and forced flow test facility (FFTF). The forced flow generator (FFG) which can provide supercritical helium up to 3 g/s with 8 atm and 4.5 K was firstly fabricated for fundamental investigation of forced-cooling coils and coolant. As the second step, STF and FFTF were constructed in order to investigate coolant, supercritical helium, control technique combined with the helium liquefier/refrigerator. They are designed to have the capacities of flow rate up to 20 g/s and 60 g/s with 15 atm and 4.4 K by adding supercritical heat exchanger to the existing 350-l/h and 1.2-kW helium cryogenic system. Using these facilities, several forced-cooled superconducting coils with cable-in-conduit conductor were tested and the stability characteristics and supercritical helium behavior in the conductor were measured. This paper describes design concept and tested performances for the forced flow facilities, and pressure rise Characteristics of supercritical helium in cable-in-conduit conductors.         Vapor-cooled lead and stacks thermal performance and design analysis by finite difference techniques    S. Peck, J. O'Loughlin and E. Christensen Summary: Investigation of the combined thermal performance of the stacks and vapor-cooled leads for the Mirror Fusion Test Facility-"B" (MFTF-B) (Figure 1) demonstrates considerable interdependency. For instance, the heat transfer to the vapor-cooled lead (VCL) from warm bus heaters, environmental enclosure, and stack is a significant additional heat load to the joule heating in the leads, proportionately higher for the lower current leads that have fewer current-carrying, counter flow coolant copper tubes. Consequently, the specific coolant flow (G/sec-kA-lead pair) increases as the lead current decreases. The definition of this interdependency and the definition of necessary thermal management has required an integrated thermal model for the entire stack/VCL assemblies.         Magnet cold mass high load supports thermal response and performance design correlation    G. Jones and E. Christensen Summary: General Dynamics Convair Division's experience in the design, detail analysis, and manufacturing of structural supports for superconducting magnet cryostats suspended in a vacuum enclosure has created a data base that is well suited for the development of correlations of pertinent thermal performance criteria for stainless steel supports. The thermal requirements of these supports in fusion applications are well defined in the Mirror Fusion Test Facility (MFTF) and have been analyzed in detail for cooldown response and steady-state performance, using Convair's Thermal Analyzer computer program. From the output of these thermal conditioning simulations, correlations Were developed for magnet LHe heating from supports in terms of strut geometric parameters. These correlations enable the user to estimate conservative transient and steady-state heat loads and the approximate time that steady-state operation conditions are reached during magnet cooldown. The dependent variables employed in these correlations are primarily the geometry of the support and location of the radiation shield intercept(s) along the support. Steady-state heat load is predicted by Equations (1) and (2). Equation (3) predicts the time history of the midpoint (warmest section) of the strut between cold-end pin and LN/sub 2/intercept during cooldown. Equation (4) predicts the LHe heating history from the support during the terminal portion of the cooldown and Equation (5) predicts the total cooldown time for the strut to reach steady-state heat rate. These correlations replace the expensive, time-consuming computer simulations previously required. In addition to capabilities of determining thermal response, optimization of thermal performance through adjusting the location of the LN/sub 2/- cooled heat intercepts, LN/sub 2/-cooled liners, and radiation shields is also discussed.         Energy transfer experiments between 3 MJ and 4 MJ pulsed superconducting magnets    T. Onishi, H. Tateishi, K. Komuro, K. Koyama, M. Takeda and T. Ichihara Summary: The pulsed power supply system for a 3 MJ pulsed superconducting magnets by using an energy storage magnet and a transfer circuit was constructed. It is composed of both 3 MJ and 4 MJ pulsed superconducting magnets (named PSM-3 and SMES-4, respectively) and the energy transfer apparatus which consists of the chopper circuit with a capacity of about 5000 kW. The reversible energy transfer experiments between SMES-4 and PSM-3 were carried out, and with the SMES-4 charged up to 4.24 MJ initial energy, the PSM-3 was successfully charged up to 2.45 MJ (4950 A, B/sub m/: 5.94 T) in 1.5 seconds and also up to 2.9 MJ (5400 A, B/sub m/: 6.48 T) in 3.0 seconds. The maximum delivery power was about 3270 kW. The energy transfer efficiency in one way transfer was about 93 %, and the current ripple was less than 0.01% of a rating current. The two pulsed magnets showed very stable performances during the energy transfers.         Power charging and discharging characteristics of SMES connected to artificial transmission line    T. Nitta, Y. Shirai and T. Okada Summary: To consider the characteristics of SMES and to investigate problems on the operations of SMES in power systems, we carried out some experiments on an experimental network. In the network, a small superconducting magnet is connected to a small synchronous generator through a double thyristorized converter and transformers. The generator is connected to the regional power system through artifitial transmission lines, AC power into or out of SMES and reactive power are controlled. Furthermore, a computer simulation program is made for the experimental system. The results of the simulation are compared with those of the experiments. For the experiments and the simulation, the harmonics current-flow, power-flow, characteristics of the generator and so on, are discussed.         A one-phase dual converter for two quadrant power control of superconducting magnets    M. Ehsani, R. Kustom and R. Boom Summary: This paper presents the results of theoretical and experimental development of a new dc-ac-dc converter for superconducting magnet power supplies. The basic operating principles of the circuit are described followed by a theoretical treatment of the dynamics and control of the system. The success ful results of the first experimental operation and control of such a circuit are presented and discussed.         Experimental studies of current sharing in parallel driven Graetz bridge units for diurnal superconductive magnetic energy storage    R. Kustom, J. Skiles, S. Akita and H. Okada Summary: Superconductive Magnetic Energy Storage (SMES) coils for diurnal load leveling and system peaking are envisioned to operate at hundreds of thousands of amperes and a few kilovolts. The interface between the SMES coil and the electric utility is envisioned to be Graetz bridges using SCR switches. Many parallel SCR switches or bridge units will have to operate in parallel because of the high operating current of the coil. Current balancing on parallel Graetz bridges driving a single 8-hy superconducting coil has been achieved on a laboratory model using delay-angle control with an LSI 11/2 microprocessor and external digital control hardware.         Optimization of Nb/sub 3/Sn    M. Suenaga Summary: Considerable progress has been made in the fabrication of large quantities of Nb/sub 3/Sn multifilamentary wires, and a number of small and large magnets have been produced successfully using these wires. However, demands for increased critical-current densities J/sub c/in the medium magnetic field range (8-12 T) as well as at very high fields (16-20 T or greater) are now being made in order to reduce the cost and to increase the efficiencies of large machines (fusion reactors and high-energy particle accelerators). In order to help meet these demands, some improvements have recently been made in increasing J/sub c/of Nb/sub 3/Sn, e.g., Ti additions to Nb/sub 3/Sn. In this presentation, the characterization of Nb/sub 3/Sn for physical properties (resistivity, lattice parameter, chemical compositions at the grain boundaries and in the bulk, etc.) and for microstructural and chemical properties will be reviewed and those properties which are particularly important in producing high values of J/sub c/will be discussed.         Microstructure development in bronze route Nb/sub 3/Sn and (Nb,Ta)/sub 3/Sn multifilamentary composites    N. Pugh, J. Robertson, E. Wallach, J. Cave, R. Somekh and J. Evetts Summary: Electron microscopy has been used to characterize the microstructure of commercial binary and ternary Al5 multifilamentary composites. TEM sections have been prepared using ion beam milling from samples reacted for various times at temperatures in the range 650- 800/spl deg/C. Layer growth kinetics have also been investigated using a combination of SEM and low temperature inductive measurements. The presence of a band of columnar grains adjacent to the refractory core is confirmed in all cases and is particularly marked at the lower temperatures. As layer growth proceeds, the columnar structure develops into an equiaxed grain structure; the mean grain size depends on the core composition. On the basis of this microstructural investigation and precise measurements of filament volume and length changes during reaction, it is proposed that the mechanism for microstructure modification is stress driven grain boundary sliding. A model describing this process is summarised.         Properties of idealized designs of Nb/sub 3/Sn composites    D. Smathers, K. Marken, P. Lee, D. Larbalestier, W. McDonald and P. O'Larey Summary: A series of seven idealized bronze-Nb/sub 3/Sn composites were manufactured by the MJR process with varying matrix to filament ratios and pure Nb and Nb 0.8 wt.% Ti cores. The central core of each composite was sealed by a diffusion barrier which results in each filament having an identical source of tin. Initial evaluations of the composites from critical current and transmission electron microscopy measurements are presented and their properties compared to standard MJR composites. The Nb/sub 3/Sn current density does not appear to be a strong function of bronze to Nb ratio over the range 2.4 to 3.2:1. The standard MJR composites have higher critical current densities than the idealized composites. It is proposed that the major reason for the increased current density of the normal MJR conductors is the intrinsically higher quality of the filaments close to the central tin core. It is postulated that the high Sn content of the bronze surrounding these filaments leads to an intrinsically higher Nb/sub 3/Sn filament current density.         The microstructural state of Nb/sub 3/Sn in a multifilamentary titanium doped bronze-process wire    P. Johnson-Walls, D. Dieterich, W. Hassenzahl and J. Morris Summary: The addition of titanium to bronze-processed Nb/sub 3/Sn wires is known to increase the upper critical field and thus improve the high field performance. High resolution studies were done to determine the effect, if any, on the microstructure caused by Ti addition. This work used a Hitachi wire with a Nb filament diameter of 3.5 /spl mu/m and a bronze to niobium ratio of 2.5. The bronze matrix had 7.5 at.% Sn and 0.4 at.% Ti. The microstructure of the Nb/sub 3/Sn layer was studied in TEM on axial and longitudinal wire sections and in SEM on fractured wire surfaces. The results were compared with a previous study on a similiarly processed Ti free wire. It was found that the Ti addition caused no qualitative change in the microstructure. This result is contrasted with previous work on the beneficial effect of Mg additions which have been shown to be predominantly microstructural.         Origin of the B/sub c2/ enhancement in ternary Nb-Sn phases    R. Bormann, D.-Y. Yu, R. Hammond, T. Geballe, S. Foner and E. McNiff Summary: Nb-Sn-Ga alloys were chosen as a model system in order to investigate the influence of third element additions on the normal and superconducting properties of alloyed Nb/sub 3/Sn phases. With respect to compositions formed by the bronze process (with Ga added to the Cu Sn matrix) alloys with concentrations close to the Sn-rich side of the A15 phase boundary were prepared. The analyses based on the GLAG theory shows that inspite of a decrease in the density of states at the Fermi level with increasing Ga content the upper critical field, B/sub c2/, is increased due to a large enhancement of the residual resistivity. However, Ga destabilizes the stoichiometric composition of the A15 phase and the critical temperature decreases for higher Ga contents. Therefore, B/sub c2/maximized at 1 to 1.5at% Ga for reaction temperatures at 700/spl deg/C. High critical fields up to 31.5 T (at T = 4.2K) have been achieved for higher reaction temperatures, which shift the phase boundary of the A15 phase field towards stoichiometry.         Critical magnetic field of V/sub 3/Ga thin films with third element additions    P. Tedrow, J. Tkaczyk, R. Meservey, S. Bending and R. Hammond Summary: We have made thin films of V-Ga superconductors by electron beam codeposition with approximately one percent additions of Nb, Ta, Sn, Pt or Pb. We have measured the high-magnetic field properties of these films to observe the effect of these impurities on spin-orbit scattering. Although the residual resistivity of the films was affected by the additional elements, the rate of spin-orbit scattering did not appear to increase.         Author Index (1984)    No author information available Summary: Not available

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