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1976     Front Cover (1976)    No author information available Summary: Not available         Table of Contents (1976)    No author information available Summary: Not available         Conference Information (1976)    No author information available Summary: Not available         Editor's comments (1976)    B. Strauss Summary: Not available         Chairman's comments (1976)    T. Geballe Summary: Not available         The why's and wherefore's of the applied superconductivity conference    C. Laverick Summary: Not available         Comments on superconducting science and technology    J. Bardeen Summary: At present a large part of scientific work, both experimental and theoretical, in superconductivty is stimulated by applications. The two most active areas are (1) nonequilibrium phenomena in superconductors, stimulated by applications based on quantum aspects and (2) research on the electron-phonon interaction and other factors that determine the transition temperature, T/sub c/, stimulated by the search for high T/sub c/materials. It is suggested that large scale applications, such as to the electric power industry, would be aided by more basic research by university scientists and engineers on the mechanical and electro-magnetic properties of currently available materials that operate at liquid helium temperatures.         New directions in fusion magnet development    C. Henning Summary: As part of the ERDA Division of Magnetic Fusion Energy effort to achieve fusion power by the end of the century, superconducting magnet programs were established at several of the national laboratories with the support of numerous industries. Recently, these program goals have been reviewed and modified to reflect new directions in fusion research. The development of superconducting toroidal field coils has been assigned first priority for the Experimental Power Reactor. This effort, centered at ORNL, will have the extensive support of industry, so that large construction capability can be encouraged. Ohmic heating coils for tokamaks promise to be an even more difficult task, and an expanded effort will be initiated as funds become available. Magnets for mirror confinement systems should have the highest fields practical. Accordingly, LLL has been funded to develop multifilamentary niobium-tin for future might experiments. If successful, the material might complement the recent trend toward higher field tokamaks as well. Energy Storage development at LASL is concentrating on inductive storage for 1 msec discharge and a superconducting homopolar generator for 30 msec to 1 sec discharge times. The stainless steel structure is a major cost element of any magnet system. However, recent calculations have shown that a magnetic coil form affects the toroidal field ripple in the EPR by only a few parts in a thousand. Thus, an opportunity exists to characterize and develop less expensive alloys for low temperature magnet structures.         Stabilization of large superconducting magnets: Experimental models    Y. Iwasa, M. Leupold and J. Williams Summary: The four experiments reported here address the problem of stabilization in large superconducting magnets. The first two experiments concern frictional heating caused by conductor motion; the last two experiments measure minimum quench propagation currents in simulated cooling conditions.         Investigation of stability of composite superconductors in typical coil configurations    J. Miller, J. Lue and L. Dresner Summary: The stability of various composite conductor designs in realistic coil environments has been examined. We measure the velocity of propagation or contraction of a normal region, the full recovery current, and the minimum propagating current in a coil segment. We examine the dependence of these measurements on background field, transport current, electrical insulation, cooling passage size and orientation, and proximity of other conductors. Comparison of experiment and calculation provides indirect information about local heat transfer to the helium bath and direct information about safe operating current limits for particular coil designs.         Quench development in magnets made with multifilamentary NbTi cable    R. Flora, M. Kuchnir and A. Tollestrup Summary: An experimental study of the normal zone propagation and total resistance as a function of time is described. The normal zone propagation velocity in a single strand was measured as a function of both current and magnetic field with particular interest in the neighborhood of the short sample limit. The study proceeded from measurements in single multifilamentary strands to measurements in 23 strand cables under different cooling environments to finally measurements in actual ramping dipole magnets made with this cable. Interpretation of the results led to the determination of safety limits for the Energy Doubler/Saver magnets and to safeguards implemented by an energy dumping circuit which effectively protects these magnets from self-destruction.         ORPUS-1 - A pulsed superconducting solenoid    R. Schwall Summary: A recent series of reference designs for Tokamak Experimental Power Reactors (EPR's) has indicated that superconducting poloidal field (PF) coils will be necessary for successful operation of these devices. It would also be desirable to use superconducting PF coils in earlier tokamak fusion devices if such coils could be developed quickly enough. In this paper, the PF coil performance requirements are briefly reviewed and some implications for the coil design are developed. A small coil (stored energy 14 kJ) has been built using construction techniques similar to those which could be employed for PF coils. The coil has been charged at rates up to 2 T/sec. Both maximum field and charging rate were limited by available power supplies. Loss measurements were carried out during pulsed operation and data for hysteretic and eddy current loss are presented. The loss measurement system used allows considerable insight into the effects of conductor motion and training.         A 17.5 Tesla superconducting concentric Nb/sub 3/Sn and V/sub 3/Ga magnet system    W. Markiewicz, E. Mains, R. Vankeuren, R. Wilcox, C. Rosner, H. Inoue, C. Hayashi and K. Tachikawa Summary: A superconducting magnet system has been designed and constructed; it now operates to a field of 17.5 Tesla. The system consists of an outer Nb/sub 3/Sn solenoid with a 160 mm bore producing 13.5 T, and an inner V/sub 3/Ga solenoid with a 31 mm bore producing an incremental 4 T. Electrical transients were monitored in the outer magnet during normal transition and compared with predictions. The inner magnet operates close to the critical current of the V/sub 3/Ga as measured in small coil tests. The magnet system was driven normal several times at a stored energy level of approximately 1.8 Megajoules, activating protective circuitry, designed to safely dissipate the energy released.         Defining critical current    A. Clark and J. Ekin Summary: The critical current of a practical superconductor can be defined in a variety of ways such as a specific voltage level, an apparent resistivity, or even the point of the irreversible superconducting-to-normal transition. The resultant values may differ very little or be meaningless for one given condition, but when comparing superconductors under a variety of conditions, such as different magnetic fields or applied stresses, these various definitions can give apparently different behavior. This is illustrated using data on the effects of stress on the critical current behavior in wires. As part of an initial effort at the National Bureau of Standards to develop standard practices and definitions for practical superconductors, several critical current criteria are proposed and discussed.         Josephson quantum interference computer devices    H. Zappe Summary: Josephson devices are potential elements for ultra-fast computers. Rather complex logic and memory circuits have been realized. Here quantum interference devices with improved speed and power performance are discussed. Latching and non-latching logic operation is possible and experiments with non-latching circuits are reviewed. Memory applications of quantum interference devices are also considered.         Memory and logic circuits using semiconductor-barrier Josephson junctions    W. Lum, H. Chan and T. Van Duzer Summary: Theoretical and experimental studies on the use of semiconductor-barrier Josephson junctions in switching circuits are reported. This work includes memory loops as well as latching and nonlatching logic circuits. It has been found previously that the switching time of a single junction (67 ps) is comparable with a similar oxide-barrier junction and that the Q of the junction is considerably lower than the oxide-barrier counterpart, as was predicted theoretically, so cavity resonance effects are nearly absent. The memory loop switching time measured is comparable with those employing oxide-barrier junction. The current experimental work on logic circuits is using semiconductor-barrier junctions as they can be made to give the desired values of the McCumber parameter /spl beta//sub c/required to achieve nonlatching operation. In all cases the junctions used are Pb-Te-Pb sandwich structures.         Single flux-quantum memory cells    P. Gueret, Th. Mohr and P. Wolf Summary: Detailed investigations have been carried out on two-junction interferometers. These devices have potential as memory elements. Information is stored as single-flux quanta (SFQ cells) in overlapping vortex modes and is destructively read out by switching from a vortex to the voltage state. The devices are fabricated with a lead alloy and the junction oxide is formed by rf oxidation. Most investigations have been done on devices with an area of about 1000 /spl mu/m/sup 2/, but storage and reading have also been demonstrated in our smallest interferometers having a size of about 150 /spl mu/m/sup 2/. Computer studies of cell properties, especially of the vortex transitions, have given good agreement with experiments. It has also been found that the cell behavior is little affected by loads such as would exist in an array environment.         A Josephson logic design employing current-switched junctions    T. Fulton, J. Magerlein and L. Dunkleberger Summary: A logic scheme using Josephson tunnel junctions in a current-steering mode is described. Switching from voltage V = 0 to V /spl neq/ 0 is accomplished by adding a fraction of the control-line currents to the bias current. In one form the addition is accomplished by shunting the junction to be switched with a loop containing a second junction serving a diode-like function and causing one or more control lines to possess inductive coupling to the loop. A five-element circuit demonstrating AND, OR and INVERSION operations carried out by this approach has been fabricated and works as expected.         Josephson tunneling logic gates with thin electrodes    M. Klein Summary: Thin electrode flux penetration effects in Josephson tunneling gates are analyzed and experimental results exhibiting these effects are reported for the first time. Deep flux penetration accompanied by deep current penetration contribute added inductance not coupled to the external field, reducing sensitivity to control current. In addition, the field within the lower electrode reduces the end-to-end asymmetry introduced by the superconducting ground plane and makes the threshold characteristic more symmetrical. The thin film effects are embodied in an equivalent circuit. Experimental results for devices with thick and thin films are compared showing the expected increased symmetry and reduced sensitivity for the thin film case. Experimental results agree well with calculations based on the equivalent circuit.         Penetration depth measurements on type II superconducting films    W. Henkels and C. Kircher Summary: A penetration depth (/spl lambda/) measurement technique, which is based upon the /spl lambda/-dependence of the propagation velocity of electromagnetic waves in superconducting transmission lines, is refined and used to accurately measure /spl lambda/'s in Pb films containing Au, In, or Bi additions. The results are applied to test two distinct predictions for /spl lambda/'s in London (or type II) superconductors. First, the measured dependence of /spl lambda/ upon low temperature electrical resistivity is compared with the theoretical prediction for a type II superconductor containing a dilute homogeneous impurity concentration. We find that the measured /spl lambda/'s follow this simple prediction reasonably well, irrespective of the species of impurity, with two anticipated exceptions. Namely, deviations occur for pure Pb, which is not a type II superconductor, and for the highest impurity concentration, in which case the Fermi surface may be appreciably distorted from that of pure Pb. Second, the London-theory prediction for the dependence of the effective penetration depth (/spl lambda//sup eff/) upon film thickness (d), /spl lambda//sup eff/= /spl lambda/(T) coth d//spl lambda/(T), is tested, in a d//spl lambda/ range in which coth d//spl lambda/, is not closely approximated by 1 or /spl lambda//d. Separate experiments in which either film thickness or temperature, T, are varied reveal excellent agreement with the above formula. To our knowledge this is the first detailed confirmation of this explicit hyperbolic cotangent dependency.         Design and test of superconducting beamline dipole magnets    R. Thome, R. Camille, H. Edwards, F. Huson, L. Kula, M. Morgan, C. Pallaver, J. Satti and A. Skraboly Summary: Two prototype superconducting beamline dipoles have been designed, fabricated, and tested. Each has an oval-shaped bore 0.095 m X 0.146 m and has an active length of about 1 m. The windings were impregnated with epoxy under vacuum and assembled on a heavy walled bore tube which provided structural support in combination with a stainless steel wire structural banding. The total amount of structural banding utilized was the major difference between magnets. The design for the magnets is described together with test results. Performance was essentially identical with each magnet requiring 14 quenches to surpass the air core central field design point of 2.5 Wb/m/sup 2/. Voltage distributions within the magnets during the quenching process were measured and controlled through utilization of a system of protective resistors. Measured results with and without the protective circuitry are given as well as calculated transients based on a simplified model.         AGS superconducting bending magnets    K. Robins, W. Sampson, A. McInturff, P. Dahl, F. Abbatiello, J. Aggus, J. Bamberger, D. Brown, R. Damm, D. Kassner, C. Lasky and A. Schlafke Summary: Four large aperture superconducting bending magnets are being built for use in the experimental beams at the AGS. Each of these magnets is 2.5 m long and has a room temperature aperture of 20 cm. The magnets are similar in design to the dipoles being developed for ISABELLE and employ a low temperature iron core. Results are presented on the "training" behavior of the magnets and a comparison will be made with the smaller aperture versions of this design. The magnet field measurements include end fields and leakage fields as well as the harmonic components of the straight section of the magnet.         A high homogeneous field superconducting magnet for Argonne polarized proton target    S. Wang, F. Onesto, D. Hill and P. Arand Summary: We have designed and built a superconducting magnet for a large polarized proton target. The magnet consists of a pair of thick Helmholtz coils. Each Helmholtz coil consists of 9 step-subcoils balancing the ampere-turns around the Helmholtz line, thus providing an optimum for field uniformity without the help of Correction coils. This magnet generates 25 kilogausses with field uniformity one part in 10,000 over more than 5 cm diameter spherical target volume. It was designed to allow a large warm bore of 34.5 cm with axial aperture of 96/spl deg/ and between the Helmholtz pair, a wide warm separation of 12.7 cm with transverse aperture of 23/spl deg/, thus allowing large accessibility to the proton target and for the scattering detectors in high energy scattering experiments.         Tests on large diameter superconducting solenoids designed for colliding beam accelerators    P. Eberhard, M. Green, W. Michael, J. Taylor and W. Wenzel Summary: Two prototype large diameter thin coil solenoids which use the mechanical structure to moderate quenches, have been built and systematically tested. The solenoids are cooled by two phase helium flowing in tubes which form a part of the coil structure. The coils have been tested by inducing a series of quenches at various currents. The results of these tests are given in this paper.         A six-tesla superconducting dipole magnet design and development program for POPAE    J. Bywater, M. Foss, L. Genens, L. Hyman, R. Smith, L. Turner, S. Wang, S. Snowdon and J. Purcell Summary: POPAE, the proposed Proton-Proton Intersecting Storage Ring Facility at Fermi National Accelerator Laboratory, will require some 1400 superconducting 6.0 T DC dipole and quadrupole magnets. The dipoles are 6. 17 m long and consist of coils of rectangular cross section clamped directly onto the 6 cm inner diameter bore tube. Aluminum is used to support the coils, and they are wound from a rectangular monolithic 2:1 copper to NbTi filamentary conductor. An experimental program has been undertaken to test and select the size, type and internal support scheme of the conductor. Individual coils of the POPAE dipole design, foreshortened to 0.5 m but supported similarly to the full-sized magnet are being tested in the field of a 2. 0 T backing magnet modeled after the Argonne SSR magnets. We also describe the large-scale cryogenics installation needed for the facility.         Operational test and field measurement of prototype bending magnets for energy saver/Doubler project    R. Yamada, H. Ishimoto and M. Price Summary: A full scale 22-foot Energy Doubler bending magnet (E22-1A) was tested in a subcooled liquid helium system. Most of the key magnetic field measurements were done on this magnet. A five-foot precision model magnet (E5-1) was tested in pool boiling helium. Much more systematic and precise measurements were done on this magnet, which was excited up to 45.7 kG at the center of the beam bore. The measurements of both magnets were done on training and quench behavior, ac loss of the magnet, and field measurements with a Hall probe. Using an NMR of a Li sample, absolute field value up to 44 kG was confirmed. Extensive harmonic analysis were done for both magnets for DC and pulsed modes. Remanent field was measured with a Hall probe and also by harmonic coil, and its variation with negative bias field was studied. The magnetically vertical plane and an effective magnetic length were measured with a stretched wire coil.         A survey of failure experience in existing superconducting magnet systems and its relevance to fusion power reactors    S. Hsieh, J. Allinger, G. Danby, J. Keane, J. Powell and A. Prodell Summary: Details of existing superconducting magnet failures are collected and evaluated with regard to future CTR superconducting magnet safety and reliability. Fourteen magnet systems with sixteen failures are presented. These failures are analyzed and categorized as to causative factors (eg. hot spots, arcing, lead failures, and conductor movement). Responses of the instrumentation and protection systems during these accident situations are also presented. Repairs and present status of the magnets are described. Preliminary conclusions are: the failure rate of existing magnet systems is too high to be tolerable for CTR magnets; although failure analyses of present systems can be used as a reference for future CTR magnet safety design, the prediction of successful operation of CTR magnet systems represents a significant extrapolation from the experiences accumulated so far; much development work and repeated testing of magnet system components and sub-systems are required.         Joining NbTi superconductors by ultrasonic welding    J. Hafstrom, D. Killpatrick, R. Niemann, J. Purcell and H. Thresh Summary: An important consideration in the design and construction of large, high-field, superconducting magnets is the capability to fabricate reliable, high-strength, low-resistance joints. A process for joining NbTi, copper stabilized, superconducting composites by ultrasonic welding is described. This process yields a joint strength comparable to that of the superconducting composite and a resistivity significantly lower than achieved by conventional soft soldering. The superconducting properties of the composite are not affected by the joining process. Scarfing the joint to maintain a constant conductor cross section does not degrade its electrical or mechanical properties. The application of the ultrasonic joining process, including process control, scarfing, and NDT procedures, in the construction of the superconducting magnet (U. S. SCMS) for the joint U. S.-Soviet MHD program is described.         Trapped fields in tape-wound cylindrical superconducting magnets    G. Donaldson and S. Penny Summary: Diamagnetic effects are most pronounced when shielding supercurrents have unimpeded paths over wide dimensions. Flat tape superconducting windings provide a good basis for study in that the shielding currents are large and calculable, and so are the resulting trapped fields at zero winding current. The investigation shows under what conditions it is necessary to allow for shielding currents, and how this may be done for maximum field calculations for magnets of cylindrical geometry. Field-dependence of critical current J/sub c/is included in both maximum field and trapped field cases. Measurements of trapped fields on two tape-wound niobium-tin magnets are shown to be in reasonable agreement with calculations. The results have been presented mainly in the form of lines of B plotted by computer. These have been most revealing, both for the trapped field, and for the maximum field where they have been compared with field lines resulting when diamagnetism is neglected.         Structural analysis of an MHD superconducting magnet    M. Srinivasan, R. Niemann, D. Krajcinovic and J. Purcell Summary: The assumptions, methods, and results of a detailed stress and deformation analysis of a large MHD superconducting circular saddle coil magnet are described. The magnet consists of a bore tube, layers of windings and filler and prestressed circumferential banding. The section at peak field is analyzed as a plane strain problem and the coil-end load effects are considered separately. Effects of each stage of loading, namely, fabrication, cool-down and energizing are determined and superposed appropriately. The elimination of the costly ring girders is shown to be acceptable. The necessity for refined forms of analysis is discussed.         Problems associated with the use of high purity aluminum in the design of composite conductors in the elasto-plastic region    S. Ladkany and W. Young Summary: High purity aluminum can apparently be used at high strain levels due to an anomalously low resistivity. However, the mechanical properties of aluminum strained to 0.003, which is unavoidable in large magnets, lead to extensive conductor confinement and support problems. High purity aluminum yields at 800 to 1200 psi which corresponds to a strain level of 0.0001 to 0.00017 at which point it becomes elasto-plastic with a small tangent modulus of approximately 0.2x10/sup 6/psi. In this region excessive plastic flow is opposed only by slight amounts of work hardening. New annular finite elements are reported for the stress analysis and strain limiting designs are given which may allow for the use of high purity aluminum in large magnets. Conceptual designs for large energy storage magnets are proposed. Experimental work is in progress; preliminary data are reported.         Reinforced aluminum as a superconducting magnet stabilizer    H. Segal Summary: The behavior of reinforced, high purity aluminum suitable for use as a superconducting magnet stabilizer has been studied. Wire samples strained cyclically exhibit a saturation value in residual resistance ratio after a few thousand cycles. The percentage change in resistance ratio from its initial value is found to be linear with strain up to strains of 0.0035 for all specimens tested so far. At 0.2% strain this change is 48% by the thousandth cycle. The transverse magnetoresistance of the composite material varies linearly above 2 tesla, which is consistent with previously published data for high purity aluminum. On the basis of these tests, reinforced aluminum appears to be quite suitable for use as a superconducting magnet stabilizer material.         Critical current changes and fatigue damage after 4.2 K strain cycling of superconducting composites    E. Fisher and S. Kim Summary: A facility for investigating the effects of cyclic strains on the current-voltage relation (I-V plots) in a superconducting composite has been constructed, as part of the conductor test program directed by Oak Ridge National Laboratory for the Tokamak Experimental Power Reactor. The initial results for a ribbon composite containing 18 Nb-Ti twisted filaments in copper showed three effects: (1) a 3% decrease in I/sub c/at 40 kOe during the initial 200 cycles at 0.35% maximum strain amplitude, (2) current sharing between filaments and copper at I < I/sub c/after cycling with maximum strain increased to 0.57% and (3) voltage steps at I > I/sub c/after 400 cycles with 0.57% strain amplitude. The first effect is consistent with I/sub c/measurements in unidirectional testing and appears to be associated with elastic strain fields. The third effect, the voltage steps at I > I/sub c/introduced by the higher strain amplitudes, decreased very significantly with increasing magnetic field and disappeared at H > 40 kOe. A Nb/sub 3/Sn composite fractured during tension-compression cycling but no damage occurred in 3800 load-unload cycles at strains up to 0.2%.         Superconductors under dynamic mechanical stress    C. Schmidt and G. Pasztor Summary: Experiments were performed to study the cause for the training phenomenon in superconducting magnets. Stress-strain curves of commercial superconductors were taken with applied field and transport current. In experiments where the samples were strained in a constant field and with a transport current below I/sub c/, the normal transition occured at successively higher stress levels. That means, a training behaviour of short samples was found. In the low strain region a distinct microplastic behaviour of NbTi wires was found by monitoring acoustic emission. The irreversibility of the detected signals indicates that mechanisms of permanent deformation exist at strain levels well below the macroscopic elastic limit. These mechanisms may be responsible for the training effect.         Stress-induced heating in commercial conductors and its possible influence on magnet performance    D. Kroeger, D. Easton and A. Moazed Summary: Calorimetric measurements show that significant amounts of heat are generated when a multifilamentary composite conductor is stressed in tension to levels expected to occur in large, high-field magnet systems. When the stress on the conductor is repetitively cycled between zero and some maximum value, the amount of heat produced per cycle is constant after the first few cycles. Comparison is made between calorimetric determinations of heat injections and the work done on the specimen as indicated by stress-strain curves. Stress-strain curves for a number of commercial conductors indicate that the most important determinant of the magnitude of this effect is the choice of matrix material.         Finite element calculation of stress induced heating of superconductors    J. Akin and A. Moazed Summary: This research is concerned with the calculation of the amount of heat generated due to the development of mechanical stresses in superconducting composites. An emperical equation is used to define the amount of stress-induced heat generation per unit volume. The equation relates the maximum applied stress and the experimental measured hysteresis loop of the composite stress-strain diagram. It is utilized in a finite element program to calculate the total stress-induced heat generation for the superconductor. An example analysis of a solenoid indicates that the stress-Induced heating can be of the same order of magnitude as eddy current effects.         Mechanisms for critical-current degradation in NbTi and Nb/sub 3/Sn multifilamentary wires    J. Ekin Summary: Critical currents of NbTi and Nb/sub 3/Sn multifilamentary wires have been studied in magnetic fields to 9 T as a function of mechanical load applied at 4 K. Degradation of the critical current in NbTi is limited to about 30% with the effect becoming large only at strains above /spl sim/ 1%. The change in critical current with strain is much larger in Nb/sub 3/Sn, commencing at strains of 0.1 to 0.3%. For both superconductors, the first 20 to 30% decrease in critical current is almost totally reversible. A number of possible explanations of the observed degradation are considered, including filament breakage, heat generation by mechanical creep, degradation of the stabilizing matrix, and defect formation in the superconductor itself. Results of experiments to test the source of degradation are reported. Evidence for microcrack damage in the Nb/sub 3/Sn reaction layer has been found and it is suggested that defect size variations on the order of a coherence length (/spl sim/ 5 nm) can account for the reversibility of the degradation as well as low-strain enhancement effects.         The development of low-loss Nb/sub 3/Sn for AC power transmission: A review    J. Bussiere Summary: A superconducting cable incorporating Nb/sub 3/Sn is briefly described and requirements for the superconductor discussed. State of the art metallurgical procedures for reducing ac losses and increasing critical currents of Nb/sub 3/Sn are reviewed. The loss behavior is then related to presently available theoretical models and shown to depend largely on surface currents which are attributed to the surface barrier. Effects of temperature, trapped magnetic flux, cladding, and cable configuration are discussed.         Electrical properties of multilayered Nb/sub 3/Sn superconducting power line conductors    R. Howard, M. Beasley, T. Geballe, C. King, R. Hammond, R. Norton, J. Salem and R. Zubeck Summary: Nb/sub 3/Sn films and multilayer composites for possible application as superconducting power transmission line (SPTL) conductors have been fabricated using electron-beam coevaporation techniques. Both growth morphology and low field superconducting properties of the conductors have been studied and compared with SPTL requirements. The behavior of the critical current as a function of temperature and magnetic field is presented together with a study of the enhancement of flux pinning due to the inclusion of thin layers of normal metal in the superconductor. Temperature and field dependence of the 50 Hz ac loss is presented and a detailed Comparison is made between the measured field-dependent dc critical current, the ac loss, the flux entry wave forms, and standard models for ac loss in the critical state. It is shown that fine-scale multilayered composite conductors can be fabricated which satisfy the ac loss and critical current requirements for SPTL operation at 10/spl deg/K on the basis of bulk properties alone without the necessity of a large surface barrier.         An analysis of the operating conditions of superconducting power transmission lines    Ye. Blinkov Summary: This paper analyzes the operating conditions of a superconducting power transmission line (SPTL), with respect to the specific features of the processes in it. The process of initial cooling of the line, its approach to steady-state conditions, energizing, load buildup, and certain dynamic and transient conditions are examined. The presence of three forms of energy flow electrical, thermal, and fluid flow) necessitated by the operating requirements of the superconducting material in an SPTL, leads to interrelated processes of electrodynamics, heat transfer and hydrodynamics. The nature of their mutual interactions determines the operational reliability of a superconducting cable system, therefore it is necessary to consider probable SPTL operating conditions and these processes in a superconducting cable and to find techniques for controlling these processes.         Power system short circuit planning for superconducting power transmission    D. Hartmann and D. Wohlgemuth Summary: Short circuit capacity of large power generation facilities is limited by the internal reactance of the generator and the impedance of connecting bus work and transformers. In the event of a fault on a generator get away circuit, d-c offset could double the short circuit current on the cable for a period of from 3 to 5 cycles after the fault initiation. High performance circuit breakers (PCBs) can shorten this fault duty time to 1 cycle (17 msec). If a superconducting cable is arbitrarily designed for 10X rated current fault withstand, its capital and operating cost may be dramatically increased. What can be done? First, a careful look at generator step up transformers and circuit breaker capability shows a marked tendency for this equipment to have very high costs if the generator bus connection scheme is planned to allow very large fault currents. However, the power system designer can set up the circuit arrangement so that massive fault currents are avoided. Second, the development of fault current limiting devices promises the possibility of holding fault current levels below 2X or 3X rated current. DC superconducting cables do not require this extra fault duty consideration, because the rectifier inverter system protects them. Usual fault conditions on d-c cable are such that less than 2X rated current will occur on the cable during a fault. Because a-c superconducting cables include very high fault current capability in their design, a careful trade-off study with current limiters, generator bus layout alternatives and possible d-c cable application should be done to assure that the final design may more readily achieve reasonable economics.         The present state and prospects of the research effort in the sphere of making flexible cryocables in the USSR    G. Meschanov, D. Belyi, P. Dolgosheev, I. Peshkov and G. Svalov Summary: Scientific investigations in the area of making flexible cryogenic cables are currently taking two main directions: the development of liquid nitrogen cooled cryoresistive cables and liquid helium cooled superconducting cables. In the first stage of our work, we carried out a technical and economic analysis of the areas of application for cryocables as well as a relative analysis of the economic characteristics of other types of power transmission lines. This analysis showed that compared with conventional underground cable systems superconducting cables have better economic characteristics at power levels above 3.0 GVA and relatively long lengths (dozens of kilometers), while liquid nitrogen cooled cables have better economic characteristics a t power levels above 0.8 GVA and shorter lengths. This paper discusses scientific investigations directed tmard the development of both resistive cryqenic and superconducting cables. The details of the technical and econcgnic analysis discussed above have previously been published and do not differ much from those generally accepted.         An efficiency comparison of superconducting transmission with other high capacity cable systems (1976)    N. Laguna, B. Belanger and A. Clorfeine Summary: The factors influencing the efficiency of power transmission cables are discussed in order to formulate a valid comparison of superconducting cables with other underground cable concepts. The sources of losses are analyzed in light of the most recent available results to compare the percent power losses of superconducting cables, other underground transmission systems, and overhead lines. Under certain conditions, superconducting cables can be extremely efficient, however, it is pointed out that superconducting cables are not necessarily more efficient than conventional transmission systems. In such cases, however, their use may still be justified on the basis of capacity and cost.         An efficiency comparison of superconducting transmission with other high capacity cable systems (Comments)    F. Edeskuty Summary: Not available         A study of electric discharges in helium at low temperatures    V. Levitov, V. Goncharov, S. Gosteyev, T. Raskatova, V. Starobinsky and A. Fatkin Summary: This paper discusses the results of a study of the electric strength of cold helium in a uniform field, when acted upon by direct, alternating, and impulse voltages. The influence of impulse slope on helium electric strength in a sharply non-uniform field is estimated, and a qualitative depiction of the discharge development is given.         The Brookhaven superconducting cable test facility    E. Forsyth and R. Gibbs Summary: Construction has started on an outdoor testing station for flexible ac superconducting power transmission cables. It is intended to serve as an intermediate step between laboratory-scale experiments and qualification testing of prototype-scale cables. The permanent equipment includes a 500 W supercritical helium refrigerator using a screw compressor and multi-stage turbine expanders. Helium storage for 250,000 cu ft of helium at 250 psi is provided. Initially, the cables will be tested in a horizontal cryostat some 250 ft long. High-voltage 60 Hz tests will be performed with the cable in a series resonant mode with a maximum line to ground capability of 240 kV, this is adequate for a 138 kV system design. Impulse testing up to about 650 kV is planned. The cable conductor will be energized by current transformers, initially at about 4 kA and later up to fault levels of 40 kA. The refrigerator is now at the site and testing on a dummy load will commence in the Fall of 1976. The cryostat will be installed in 1977 followed about a year later by the first cable tests.         Calculation of the coils for pool-boiling type superconducting magnets    V. Belyakov, V. Shaposhnikov, I. Mikhailov and S. Gorbachev Summary: The most comon type of superconducting magnet cooled by pool-boiling in liquid helium. The conductors are wound with channels allowing free circulation of liquid helium around them, which ensures cryostatic stabilization. When the current is forced out of the superconductor into the substrate as a result of a jump, the heat produced in the substrate must be transferred to the helium at a rate that limits the temperature of the superconducting winding. If the cause forces the current out of the superconductor is eliminated, the winding will return to the superconducting state. The superconducting winding of a pool-boiling magnet usually consists of a flat tape made from material with good electrical conductivity, such as copper, in which the superconducting filaments are situated. The windings consist of coils of the composite conductor wound on spacers to provide channels circulation of the helium refrigerant.         Electrical, cryogenic and systems design of a DC superconducting power transmission line    H. Laquer, J. Dean and P. Chowdhuri Summary: The electrical, cryogenic, and systems design concepts for a dc superconducting power transmission line are discussed. The line consists of a hollow-core flexible coaxial cable, using multifilamentary or tape Nb/sub 3/Sn superconductor and wrapped tape dielectric, within a rigid cryogenic envelope. Cryogen flows through the core, is expanded in a turbine and returns over the outer cable surface. The concept is applied to power levels of 1 to 10 GW and for a range of line voltages and maximum dielectric stresses. Systems considerations define capacity ratings and optimum operating voltages. Cost estimates for the various components and cost optimizations are presented.         Investigations on the development of superconducting DC power transmission lines    I. Bortnik, V. Karapazuk, V. Lavrova, S. Lurie, Y. Petrovsky and L. Fisher Summary: The All-Union Lenin Electrotechnical Institute is engaged in a program to develop superconducting dc power transmission lines. Various superconducting materials have been characterized and several models of dc superconducting cables have been developed and tested.         Longitudinal and transverse field losses in multifilament superconductors    W. Carr Jr. Summary: A review is given of the method of calculating losses in a composite twisted multifilament superconductor based on the anisotropic continuum model, and a summary of results are shown for the loss as a function of frequency due to longitudinal and transverse applied fields. In both cases three frequency ranges may be distinguished in which (1) the magnetic field in the superconductor is just the applied field, (2) the field produced by internal currents becomes important, and (3) skin effect develops in the eddy currents, which flow transverse to the filaments. In addition to these losses in the body of the superconductor (characterized by a vanishing component of electric field parallel to the filament axes), the loss in the current saturated boundary layer is described. Some discussion is also given on the use of ac field losses in calculating the "ramped" field case.         Magnetic field profiles of NbTi tapes    A. Migliori, R. Taylor and R. Bartlett Summary: Magnetic field profile measurements were performed on stabilized NbTi tapes in zero applied field carrying large transport current densities. Field profile data were taken on large diameter superconducting sample loops at temperatures between 2 K and T/sub c/(about 9.2 K) and several persistent currents up to I/sub c/(T), the maximum. The field profiles scaled with current, independent of temperature, at temperatures below 8.5 K and were well described by an elliptical shell approximation which left a current-free, field-free central reqion. Critical state models applied to this self-field situation proved inadequate. Complex profiles produced by trapped flux in the tape loop were described quantitatively by assuming concentric elliptical shells each with a different current density. The maximum current which could be persisted in the loop at each temperature was linear from 4 to 8.5 K. The effective resistance of the superconducting loop including its joint was less than 10/sup -13//spl Omega/.         Dissipation in cylindrical type-II superconductors rotating in a magnetic field    R. Schafer and C. Heiden Summary: A type-II superconductor in the mixed state which rotates with angular velocity /spl omega/ in a magnetic field H/sub o/directed perpendicular to the axis of rotation experiences a retarding torque due to pinning and viscous friction of vortices. A method is presented using the critical state concept that allows one to calculate the torque and associated losses for a cylindrical specimen of radius a and infinite length, if its equilibrium magnetization curve and the dependence of its flux-flow conductivity /spl sigma//sub f/and critical current density J/sub c/on the macroscopic flux density B are given. Results obtained for a substance with simple model behavior of /spl sigma//sub f/(B), J/sub c/(B), and magnetization are discussed. For constant a and H/sub o/, a linear variation of the torque per unit length with /spl sigma//sub f//spl omega/ and with J/sub c/is observed for sufficiently low values of these parameters. At higher values, a deviation from this behavior results from vortex curvature combined with strong flux-density gradients and from increasing explusion of flux from the sample.         Field replication and flux shielding in annular superconductors    D. Frankel and E. Garwin Summary: The phenomenon of flux trapping in type II superconductors can be exploited by fabricating simple, tubular assemblies of bulk or layered superconductors which then accurately preserve a wide variety of field configurations. The associated flux shielding properties can be used where field free regions are required. The results of flux trapping and shielding experiments on samples of vapor deposited Nb/sub 3/Sn, bulk Nb-Ti, Nb-Ti/Cu sheet-composite, and bulk Pb-Bi are reported. Measurements of the magnetic field in the vicinity of the samples as a function of position and applied field produce field profiles and magnetization-like curves. The experimental curves are related to critical state models and together with an appropriate model give estimates of critical currents in the materials. The occurrence and extent of the flux jumps, which often limit flux trapping and shielding capabilities, are compared with predictions of stability models. Heat- and surface-treatments which increase pinning strengths and trapped flux are described.         Orientation effects on the magnetization of NbTi superconductors    K. Jungst Summary: Magnetization measurements in slowly varying fields have shown an anisotropy of pinning forces and of hysteretic losses for different angles /spl alpha/ between conductor axis and magnetic field. With decreasing /spl alpha/ the hysteretic losses are growing and catastrophic flux jumps appear depending on magnetic history. At intermediate angles alterations in shape of the magnetization curve are observed which may be due to flux lines inclined to the external field. Moreover, in twisted multifilamentary wires fast pulsed longitudinal fields influence the area of the magnetization curve as well as its shape and position.         A computer program to calculate composite conductor losses in pulsed poloidal coil systems    W. Gray and J. Ballou Summary: In the design of the cryogenic system and superconducting magnets for a poloidal field system in a tokamak fusion reactor, it is important to have an accurate estimate of the heat produced in the superconducting magnets as a result of the rapidly changing magnetic fields. Until recently, this estimate was obtained by assuming that the field and the time rate of change of the field were constant throughout the coil windings. A more accurate method of estimation involves integrating the losses over the coil windings, thus taking into account the spatial variation of the magnetic field. A computer code, PLASS (Pulsed Losses in Axisymmetric Superconducting Solenoids), has been written to perform this integration. PLASS has been used to analyze the present design for the poloidal coil system of the ORNL Experimental Power Reactor (EPR). This design requires that superconductor hysteresis losses, superconductor coupling losses, stabilizing material eddy current losses, and structural material eddy current losses be taken into consideration in the calculation of conductor losses. A tabulation of individual losses vs variations in superconductor characteristics and coil current changes is presented to demonstrate the parameters which significantly affect the design. Results indicate that the total energy released into the cryogenic system is less than one-half of that predicted by the previously oversimplified calculation.         AC losses and critical current in an aluminum stabilized mixed matrix NbTi superconductor composite    G. Wagner, M. Walker, D. Koop and C. Whetstone Summary: AC losses were measured for a twisted (L = 1.57 cm) superconductor wire (0.16 cm O.D.) consisting of 54 NbTi tubular filaments which were filled with high purity aluminum stabilizer and imbedded in a high strength aluminum alloy matrix. The measurements were made at 4.2 /spl deg/K in bias fields of zero and five Tesla as a function of ac field amplitude and frequency (1 Hz /spl leq/ f /spl leq/ 20 kHz). AC field amplitudes which are less than necessary to fully penetrate the filaments were used throughout the experiment. At frequencies lower than about 10 Hz the losses are dominated by partial penetration hysteresis effects while at higher frequencies eddy current losses dominate. The eddy current losses were calculated using the anisotropic continuum model developed by Carr and co-workers and good agreement between theory and experiment was obtained over the entire frequency range from 10 Hz to 20 kHz. Critical current vs bias field measurements were also carried out. At /spl rho/ = 10/sup -11//spl Omega/cm the J/sub c/in the NbTi was found to be 1.17x10/sup 9/A/m/sup 2/and 1.40x10/sup 9/A/m/sup 2/in fields of 5 T and 4 T respectively. At lower fields the sample quenched before showing a measurable resistive onset. The value of J/sub c/measured at 5 T is in excellent agreement with that calculated from the partial penetration hysteresis losses observed at low frequencies.         The super-Schottky microwave mixer    M. McColl, M. Millea, A. Silver, M. Bottjer, R. Pedersen and F. Vernon Jr. Summary: The super-Schottky diode has now achieved the lowest reported NEP and mixer noise temperature at X-band: 5x10/sup -16/W/Hz/sup 1/2/and 6 K, respectively at an operating temperature of 1.1 K. Diode fabrication, mixer construction, and extensive microwave performance measurements as a function of such operating parameters as temperature, LO power, and dc bias are reported. Extension to millimeter wavelengths requires further reduction in parasitic losses while retaining the low impedance nonlinearity from the superconductive single particle tunneling. Material and geometric design parameters are discussed and applied to the III-V semiconductors. A comparison of experimental results for GaAs with theory and the near term potential is discussed.         Experimental investigation of the microwave-impedance peculiarities of superconducting thin-film bridges    V. Gubankov, V. Koshelets and G. Ovsyannikov Summary: The anomalous microwave impedance effect of variable-thickness tin bridges of submicron dimensions has been observed and investigated. The peculiarities of real and imaginary parts of the bridge microwave impedance for a variety of bias, temperature and incident microwave power have been explored for different values of the characteristic parameter V/sub o/of a Josephson junction. Experimental conditions of correct comparison of obtained results with the theory have been analyzed.         One-frequency parametric amplifier using self-pumped Josephson junction    A. Vystavkin, V. Gubankov, L. Kuzmin, K. Likharev, V. Migulin and V. Semenov Summary: Gain and noise properties of a non-degenerate one-frequency parametric amplifier using a self-pumped Josephson junction are investigated both theoretically and experimentally. The amplifier uses the phenomenon of microwave negative resistance of the junction. Theoretical analysis made in usual resistively shunted junction (RSJ) model shows that the minimum noise temperature is equal to approximately 42T. It takes place at a signal frequency f close to the junction characteristic frequency f/sub 0/. Maximum effectivity (the product of the square root of power gain and relative bandwidth) can reach 0.4 at f/spl sime/f/sub 0/. Gain up to 20 dB was obtained at X-band using amplifier with Nb-Ta point-contact junction. Minimum noise temperature at T = 4.2K was about 200K.         Josephson junction as F-band mixer-multiplier    V. D'yakov, V. Gubankov, A. Spitzin and A. Vystavkin Summary: Properties of a niobium-niobium Josephson superconducting point contact (SPC) used as a mixer-multiplier have been investigated experimentally. Conversion of a microwave signal with frequency f/sup s/= 127 GHz into a signal with the intermediate frequency f/sup if/= 8.6 GHz has been obtained using heterodyne generators with frequencies f/sup h/= 136.68, 45, and 6.8 GHz, so that f/sup if/= nf/sup h1,2,3 ....20/- f/sup s/where n = 1.2, 3.20 are heterodyne harmonics produced in the SPC. Dependences of the conversion efficiency (/spl eta//sub n/) on the bias voltage, the heterodyne power and the heterodyne harmonics have been measured. In the case of the second and the twentieth harmonics, the best value of /spl eta//sub 20///spl eta//sub 2/was 0.25. This value is essentially higher than that obtained for the usual (conventional) semiconducting mixer. Performed experiments have demonstrated the perspective of utilization of SPC as a mixer-multiplier in millimeter and submillimeter wavebands.         Limit characteristics of two-junction magnetic flux detector    V. Danilov, K. Likharev, O. Sniguiriev and E. Soldatov Summary: The sensitivity of a two-Josephson-junction interferometer as a magnetic flux detector (dc SQUID) is estimated. The minimum value of the basic SQUID characteristic-noise equivalent temperature /spl delta/T = (/spl delta//spl Phi/)/sup 2//k/sub B/L appears to be as low as for the best rf SQUID mode: (/spl delta/T)/sub min//(/spl Delta/f)/spl cong/ 3 T/f/sub o/. Here T is an operating temperature, f/sub o/is a characteristic frequency of the Josephson junctions and /spl Delta/f is a post-detector bandwidth. For a typical value of SQUID inductance L this limit corresponds to flux sensitivity of the order of 10/sup -7//spl Phi//sub o//Hz/sup 1/2/.         Dynamics of some single flux quantum devices: I. Parametric quantron    K. Likharev Summary: In this paper and the following one, the properties of two systems operating with single flux quanta are calculated. The first system is a quantron (a one-junction interferometer) with a Josephson gate as a junction. By a proper change of its critical current in time, the switching of quantron stable states can be controlled by a small external flux much less than /spl Phi//sub o/. This "Parametric Quantron" can be used as the basic cell of a Single Quantum Logic System. The most wonderful property of this device is that the energy dissipation during one logical step (P/spl tau/T factor) can be much less than the thermal energy K/sub B/T and is limited by quantum effects only: P/spl tau//sup 2/\simg10/sup 2/h.         Dynamics of some single flux quantum devices: II. Inhomogeneous flux shuttle    K. Likharev Summary: In this report we discuss the properties of a "flux shuttle", similar to that described recently but with its parameters depending periodically on the coordinate along the length of the structure. In the case of a proper choice of the parameters a one-directional shift of vortices (flux quanta) appears to be possible along the structure, induced by ac current flowing directly in the superconducting electrodes. The shift for one structure period takes typically one psec and does not pertrub the relative distance between vortices of any sign (orientation).         Microwave generation and complex microwave responsivity measurements on small Dayem bridges    N. Pedersen, O. Soerensen, J. Mygind, P. Lindelof, M. Levinsen, T. Clark and M. Danielsen Summary: Measurements of the active properties of a Dayem micro-bridge at X-band frequencies is described. The bridge was mounted in a microwave cavity designed to match the bridge properly and the microwave output from the cavity was detected using a sensitive X-band spectrometer. Microwave power was detected from the freely running Josephson oscillations with the bridge dc-biased to emit at the receiver frequency and the maximum power extracted was of order 10/sup -12/W when the receiver was tuned to the cavity resonance. With an external rf-excitation of the bridge the amplitude of either the first or second harmonic response was measured. On the basis of analogue computer simulations an equivalent circuit was obtained describing the bridge coupled to the cavity. The large self inductance of the background film adjacent to the bridge was found to play a major role in explaining our results.         A Josephson effect parametric amplifier at 36 GHz    Y. Taur and P. Richards Summary: Doubly degenerate parametric amplification by a point contact Josephson junction is observed at 36 GHz. The best amplifier showed a net gain of 11 dB and a noise temperature less than 50 K.         Superconducting generators for utility power systems    M. Rabinowitz Summary: The concept of a superconducting ac generator for utility power system applications has been of interest for a number of years, but it has not been until recently that definitive feasibility studies have been made. Although these studies are not yet complete, it appears that among the advantages to be accrued will be reduced size and weight, higher efficiency, lower capital cost, and greater stability. In addition to these detailed design programs at Westinghouse and General Electric, the Electric Power Research Institute is sponsoring exploratory research for even more advanced generating concepts at the Massachusetts Institute of Technology, Case Western Reserve University, and Battelle Pacific Northwest Laboratories. If successful, the ac superconducting generator may well be the first large scale commercial application of superconductivity. In part, this is because the anticipated advantages should occur at present power generation levels (/spl sim/1000 MVA), rather than at future power levels.         Air force applications of lightweight superconducting machinery    C. Oberly Summary: The U.S. Air Force has actively developed superconductor technology since 1961. Early Air Force involvement was disappointing due to the primitive technological state of superconductivity in the mid- 1960's. Following the successful application of stability theories, programs in the areas of superconducting alternators, magnetohydrodynamic (MHD) generator coils and inductive energy storage coils have been productive. The universal Air Force requirement for lightweight machinery eliminates cryostatic stability from consideration for lightweight designs of superconducting coils. Maximum overall current density is necessary. Serious transient field losses are induced by armature currents in synchronous alternators, conductive gas currents in MHD generators and discharge currents in energy storage coils. Shock and vibration structural support of the superconductor to prevent motion induced quenches remains a challenge to the machine designer. Exotic superalloy or advanced composite structures are required to achieve high stiffness and lightweight. Development of flexible multifilament Nb/sub 3/Sn is underway to create thermal margin for superconducting machinery. The problems of achieving ultra-lightweight performance are reviewed with special emphasis on the interrelated problems of potting, structural support and cooling at high current density in an environment of transient magnetic field. Second generation machinery development programs are beginning. With acceptance of superconducting systems and attendant cryogenic support problems, wider application of superconducting machinery may result.         Superconducting machinery for naval ship propulsion    H. Stevens, M. Superczynski, T. Doyle, J. Harrison and H. Messinger Summary: The Navy is developing the technology base for superconducting electric propulsion machinery systems for ship drives in the range of 40,000 to 75,000 hp per shaft. Full scale system development is aimed at the 1980-85 period. Current progress includes design, construction and tests of laboratory superconductive machinery in the 400 to 1000 hp range, preliminary design of 40,000 hp systems and ongoing construction of 3000 hp feasibility models of full scale systems. The objectives, scope, technical content and current progress of this program are presented. Brief technical discussion of the areas of machine design, liquid metal current collectors, superconducting magnet-dewar construction, and helium refrigeration development is included.         ISABELLE Ring Magnets    A. McInturff, W. Sampson, K. Robins, P. Dahl, R. Damm, D. Kassner, J. Kaugerts and C. Lasky Summary: Data are presented to establish the operating characteristics of the proposed ISABELLE Ring Magnets. The harmonic content of both the straight section and ends of the magnets was measured as a function of magnetic field with the correction coils energized or disconnected. The magnets are single layer cos N/spl theta/ turns distribution superconducting saddle coils with 'cold' iron shields. The data presented also include quench performance of magnets vs the critical current performance of the wire strands; the rate effect on the harmonic content of the field; the magnetization loss of the magnets; magnetic length; magnetic field vs current/turn; and magnetic field external to the iron shield. The maximum performances of the dipoles and quadrupoles are 4.9 T and 4.6 T (bore field 2-D) with a design requirement of 3.93 T and 3.28 T respectively. Magnets of both types have exceeded the design field on the first quench. The field characteristics are well within the present design requirements for ISABELLE.         The technology of producing reliable superconducting dipoles at Fermilab    W. Fowler, P. Livdahl, A. Tollestrup, B. Strauss, R. Peters, M. Kuchnir, R. Flora, P. Limon, C. Rode, H. Hinterberger, G. Biallas, K. Koepke, W. Hanson and R. Brocker Summary: During the last few months several full size prototype dipole magnets for the Fermilab Energy Doubler have been successfully tested. This has been the result of several concurrent programs in the conductor development as well as the magnet construction, production and testing. We consider that our present magnets have achieved their design goal. Progress to this point has solved many pitfalls. We will describe our present technology as well as some of the decisions that leg to our present design.         ESCAR mid-term report    T. Elioff, R. Byrns, W. Gilbert, G. Lambertson and R. Meuser Summary: The LBL Advanced Accelerator Group is now well in to the design and fabrication of a small pilot-project accelerator and storage ring using superconducting magnets. This project has the acronym ESCAR, which stands for Experimental Superconducting Accelerator Ring. One refrigeration building has been completed, and detailed drawings are being prepared for other conventional facilities. The accelerator layout and machine components are in fabrication.         A multifilamentary Nb/sub 3/Sn dipole magnet    W. Sampson, M. Suenaga and S. Kiss Summary: A one meter long, 8 cm aperture dipole magnet has been constructed from prereacted Nb/sub 3/Sn multifilamentary conductor. The conductor is in the form of a wide braid formed from 95 wires of 0.3 mm dia. each containing 1045 filaments of niobium in a copper-tin matrix. After braiding and compacting the conductor was heat treated to form the Nb/sub 3/Sn filaments. The braid was then wound into a dipole of the ISA type using techniques similar to those employed in the construction of magnets from the more conventional NbTi braid. Voltage taps were attached to the conductor at appropriate positions so that the effect of mechanical stress could be observed at the bends of greatest curvature. The effective resistivity of the bent regions of the conductor showed a marked dependance on the bend radius varying from 7x10/sup -10/ohm-cm at a radius of 0.6 cm to approx, 10/sup -10/ohm-cm at 1.0 cm measured at a field of 3 T and a current density of 3.7x10/sup 4/Amps/cm/sup 2/. While the bending of the conductor during coil fabrication did lead to some damage of the Nb/sub 3/Sn filaments, it was not the factor limiting coil performance. The connection between the coil halves in the magnet was resistive and limited the maximum coil current to 2650 amps, well below the short sample limit. An improved method of coil interconnection is being used in future magnets in this series and should make it possible to extend the measurements to higher fields and current densities.         Design and construction of superconducting quadrupole magnets at Karlsruhe    F. Arendt, N. Fessler and P. Turowski Summary: Two types of superconducting quadrupole magnets have been developed: 6 extremely short doublets with a quadrupole length of nearly 11 cm as beam focusing elements in the Karlsruhe superconducting proton linac; 2 quadrupoles of about 1 m length for use in the hyperon experiments at the CERN SPS. The concept for these quadrupoles is a one current block winding per pole, calculated with respect to minimum field errors. Special mechanical and winding techniques have been developed to get the high geometric accuracy required for such air coils. The short doublets must be operated in persistent current mode with a thermal superconducting switch and a required time constant of /spl tau/ > 10/sup 4/hours. The hyperon beam quadrupoles must operate reliably for a long time in an inaccessible concrete shielding. The performance of the quadrupoles will be reported.         Design and operation of a superconducting high energy beam line at the Argonne National Laboratory zero gradient synchrotron    J. Bywater, C. Brzegowy, J. Dvorak, R. Fuja, H. Ludwig, K. Mataya, R. Moffett, R. Niemann, S. Wang and J. Purcell Summary: A superconducting high energy physics beam line 60 meters long is now operating at the Argonne National Laboratory Zero Gradient Synchrotron (ZGS). The line transports 12 GeV/c polarized protons to a large particle spectrometer. It consists of ten superconducting dipoles, two superconducting quadrupoles, and several conventional magnets. The superconducting magnets are contained in four cryostats; three 3-dipole cryostats, each 3.5 meters long; and one quad-dipole-quad (QDQ) cryostat 2.7 meters long. The superconducting magnets have a useful aperture of 7.6 cm diameter. At 12 GeV/c the dipoles operate at 2.6 T over 91 cm, with 160 amperes, and the quadrupoles at 0.31 T/cm over 41 cm, with 190 amperes. The cryostat installation, initial cooldown, boil-off gas recovery system, power supply controls, beam optics, and operating experience are presented.         Investigation of two identical superconducting dipoles    V. Alexeev, L. Greben, E. Mironov, L. Popokin and A. Vasiliev Summary: This report is devoted to an investigation of the identity of two dipoles SPD-3 and SPD-3' having the same construction scheme. Independent tests for each magnet were carried out in the same cryostat, including simultaneous precise measurements of field B and current I. One may consider the difference of rations K = B/I for the dipoles as a measure of the magnet identity. The value of K depends on B and rises at low B due to remanent fields. From the measurements, the difference of the curves K(B) for both magnets is about 0.1 per cent. Measured inhomogeneity across the aperture for both magnets does not exceed 4x10/sup -4/.         Progress toward a practical Nb-Ge conductor    A. Braginski, J. Gavaler, G. Roland, M. Daniel, M. Janocko and A. Santhanam Summary: Properties of high-T/sub c/Nb-Ge films deposited by sputtering and by chemical vapor deposition (CVD) have been investigated. Results of sputtering in the presence of controlled levels of O/sub 2/, N/sub 2/, Si, and of reactive sputtering in Ar-GeH/sub 4/, suggest that the high-T/sub c/A15 phase is impurity- or defect-stabilized. In CVD deposits two tetragonal modifications were found: /spl sigma/ and T2, the latter probably stabilized by C1/sub 2/. High critical current densities, J/sub c/(H, T) of fine-grained sputtered films are attributed to flux pinning on A15 grain boundaries. In coarse-grained CVD films high self-field J/sub c/s, 10/sup 6/to 10/sup 7/A cm/sup -2/at T = 4.2 K, are attributed to pinning on dispersed /spl sigma/-phase. Comparably high J/sub c/'s were also obtained in CVD A15 films doped with impurities. Low field ac losses p (H,T) were correlated with J/sub c/and coating geometries. The feasibility of fabricating multifilamentary composite conductors by CVD was demonstrated experimentally and a fabrication process for long Nb/sub 3/Ge CVD tapes is being developed.         Growth of A-15 Nb/sub 3/Ge by co-evaporation    R. Sigsbee Summary: Enhanced T/sub c/'s (/spl gt/;21/spl deg/K), T/sub c/widths and resistivity ratios result when controlled amounts of O/sub 2/are admitted during film growth. O/sub 2/levels /spl ap/ 5x10/sup -7/mm Hg stabilize the Nb/sub 3/Ge phase over a wide range of Nb/Ge flux ratios for films grown at 6A/sec and 1000/spl deg/C.         Phase diagram of electron-beam codeposited Nb/sub 3/Ge: The influence of oxygen and other gases    A. Hallak, R. Hammond, T. Geballe and R. Zubeck Summary: Oxygen, air, or chlorine gas present in the vacuum system during evaporation extend the Ge-rich boundary of the A15 phase towards the ideal 3:1 ratio. X-ray evidence indicates the presence of an amorphous component below 775/spl deg/C which is detrimental to the superconductivity and which is accompanied by an abrupt increase in the A15 lattice constant. Preliminary Auger results indicate that the Nb:O ratio first decreases as the partial pressure of O/sub 2/increases and then remains constant.         Application of high rate magnetron sputtering to the fabrication of A-15 compounds    R. Kampwirth, J. Hafstrom and C. Wu Summary: High quality Nb/sub 3/Sn films have been fabricated using a recently developed magnetron sputtering process capable of deposition rates approaching 1 /spl mu/m/min. at sputtering voltages less than 500 V and power levels of about 5 KW. Low sputtering voltages allow more complete thermalization at lower pressures of the material condensing on the substrate which can improve long range order. Transition temperatures of up to 18.3/spl deg/K, J/sub c/(O)'s of 15x10/sup 6/A/cm/sup 2/and Hc/sub 2/as high as 240 kOe have been achieved in 1-3 /spl mu/m films deposited from a Nb/sub 3/Sn reacted powder target with substrate temperatures between 600 and 800/spl deg/C. The films exhibit smooth surfaces and, generally, a <200/spl Gt/ preferred orientation. The growth of the film is columnar in nature. The sputtering parameters, substrate material and temperature will be related to film structure, T/sub c/and J/sub c/(H,T) and the Nb/Sn ratio as determined by Rutherford backscattering.         Further developments in stabilized multifilamentary Nb/sub 3/Sn superconductors    E. Adam, E. Gregory and F. Ormand Summary: A series of copper stabilized multifilamentary Nb/sub 3/Sn conductors in various configurations are described. The properties of those recently developed from a 13.5 wt % Sn bronze matrix are compared with earlier configurations made from 10wt % Sn bronze matrices. Some problems encountered in short sample testing of these materials and the performance of magnets made from them are mentioned.         Properties of RF sputtered Nb/sub 3/Ga superconducting films    R. Burt and F. Worzala Summary: Niobium-gallium films with a composition range of 8 at. % to 35 at. % Ga have been prepared using RF sputtering techniques. A variable composition sputtering target, fabricated from Nb and NbGa/sub 3/powders, was used to vary the lengthwise composition as deposited on polished Al/sub 2/O/sub 3/substrates. The effects of deposition temperature, subsequent heat treatment, and background impurity pressure during sputtering, were studied in relation to crystalline structure, film composition, resistive T/sub c/, and resistivity ratio. Maximum T/sub c/values occur in the 30 at. % Ga region of the film when gaseous impurity levels are high, and after the films are given a 700/spl deg/C vacuum anneal.         Anisotropy of critical currents and fields in sputtered and evaporated superconducting Nb/sub 3/Ge films    H. Braun, E. Haeussler and E. Saur Summary: Nb/sub 3/Ge films with thicknesses between 0.06 and 1.5 /spl mu/m were deposited onto heated sapphire substrates by dc sputtering in a pure argon atmosphere as well as by thermal coevaporation of niobium and germanium in ultrahigh vacuum. Both preparation methods result in Nb/sub 3/Ge films with high transition onset temperatures up to 22.7 K which crystallize in a single phase A 15-structure with a lattice parameter of 5.14 /spl Aring/. The sputtered films exhibit columnar growth of the crystallites normal to the substrate surface in contrast to random crystallite arrangement in the evaporated films. Critical current densities and upper critical magnetic fields were measured as a function of magnetic field orientation, temperature and film thickness. In sputtered films critical currents and fields show maxima for the field orientation normal to the sample surface, whereas in evaporated films these maxima occur for parallel field orientation.         Superconducting critical temperatures of co-evaporated Nb-Ge films    M. Kudo and Y. Tarutani Summary: Nb-Ge films were prepared by a co-evaporation technique. The dependences of critical temperature T/sub c/, lattice parameter a/sub o/and electrical resistivity /spl rho/ on deposition condition, i.e., substrate temperature, deposition rate and film thickness, were investigated. Close relations were observed not only between T/sub c/and a/sub o/, but also between T/sub c/and /spl utri//spl rho/, where /spl utri//spl rho/ is the difference between /spl rho/(300 K) and /spl rho/(25). The T/sub c/'s dependence on the film thickness was also observed. The T/sub c/'s value of Nb-Ge films was about 22 K for 2000 /spl Aring/ in thickness and below 4.2 K for 50 /spl Aring/ in thickness. From a transmission electron micrograph the Nb-Ge film was found to be a polycrystal with Nb/sub 3/Ge grains of about 500 /spl Aring/ in diameter.         Detection of superconducting inhomogeneities by penetration depth measurements /spl delta//spl lambda/ (T, f, B/sub ac/)    W. Schwarz and J. Halbritter Summary: Small regions of differently strong superconducting interaction have been detected by measuring the penetration depth /spl utri//spl lambda/(T,f,B/sub ac/) and the losses /spl utri/R(T,f,B/sub ac/) as deviation from the BCS theory of homogeneous materials. For Nb two deviations are most pronounced: a step-like increase in /spl utri//spl lambda/(T) and /spl utri/R(T) at T* /spl sime/ 7K and an enhanced slope /spl lambda//sub 0/= d/spl lambda//dy[y = 1/\sqrt{1-(T/T_{c})^{4}}]for T > T*. The step /spl utri//spl lambda//sub 0/around 7 K shows the transition of regions to the normal state, which then for T > T* yield an enhanced slope /spl lambda//sub 0/, as explained by proximity effect theory. For Nb/sub 3/Sn no such deviations from the BCS theory could be detected, showing together with /spl lambda//sub 0/= 170 nm its homogeneity. For thinned Nb/sub 3/Sn layers the underlaying Nb shows up as step at 9.2 K, which is used to evaluate the mean thickness of the Nb/sub 3/Sn layer.         Measurement of the microwave properties of superconducting Nb/sub 30/-Ta/sub 70/    C. Lyneis and J. Turneaure Summary: The low field and high field microwave characteristics of a superconducting 8.6 GHz cavity which was machined from a rod of 30 at % Nb and 70 at % Ta were investigated. The low field temperature dependence of the surface resistance was in agreement with the surface resistance calculated from the Mattis-Bardeen expression for a reduced energy gap of 3.61. The maximum critical rf field attained was 6.1 mT which is well below the value of H/sub cl/for this alloy. Thermal calculations based on a line defect model for the surface of the superconductor were made and compared with the experimental measurements. This comparison indicates a field independent defect model does not adequately represent thermal magnetic breakdown observed for the Nb/sub 30/-Ta/sub 70/cavity.         Superconducting Mo/sub 0.75/Re/sub 0.25/cavities at X-band    K. Agyeman, I. Puffer, J. Yasaitis and R. Rose Summary: RF properties of superconducting Mo/sub 0.75/Re/sub 0.25/were studied by performing rf measurements on three TE/sub 011/mode X-band cavities of the alloy. Cavity surfaces were prepared for testing by means of either electrolytic polishing or uhv anneal. From the temperature-dependent unloaded Q(Q/sub o/) of the cavities, the surface resistance of the alloy as a function of temperature, R(T), in the temperature range 4.2K to 1.4K was determined. From the R(T) plots, the residual surface resistance, R/sub o/, and the superconducting energy gap parameter, /spl utri/(0), were obtainable. The highest Q/sub o/measured was 1.4x10/sup 9/, corresponding to a R/sub o/of 5.7x10/sup -7//spl Omega/. The average value of the energy gap parameter, /spl utri/(0), was (1.78 /spl plusmn/ 0.04)k/sub B/T/sub c/. Magnetic breakdown fields, H/sub crf/, were also determined by measuring Q/sub o/as a function of peak surface magnetic field. The highest value of H/sub crf/found for the alloy was 176G. We discuss cavity performance as a function of surface preparation, aging and atmospheric exposure.         Fabrication and performance of "Muffin-tin" microwave cavities for accelerator use    H. Padamsee, J. Kirchgessner, M. Tigner, R. Sundelin, M. Banner, J. Stimmell and L. Phillips Summary: Several 1-cell, 2-cell and 6-cell s-band "muffin-tin" type cavities have been fabricated out of 1.6mm thick Nb sheet metal. Without any heat treatment, the 6-cell cavities achieved Q/sub o/'s between 3-6x10/sup 9/and effective accelerating field gradients, E/sub eff/(for electrons) up to 2.7 MeV/m. After firing at 1900/spl deg/C, Q/sub o/values between 6-14x10/sup 9/and E/sub eff/up to 6.9 MeV/m were reached. Comparable Q/sub o/values and significantly higher field values were obtained in the 1-cell and 2-cell cases. A summary of the fabrication technique together with test results are presented. We also discuss results of other tests related to cavity performance such as the visual observation of the interior of cavities during operation and a study of heat pulses detected outside the cavity during and prior to breakdown. Tests have also been made of single cell cavities on which a surface layer of Nb was deposited by sputtering. A Q/sub o/of 3x10/sup 9/and E/sub eff/of 4.3 MeV/m was achieved without any surface treatment after sputtering. We believe these results show that the sputtering technique is capable of producing high quality RF surfaces.         Microwave non-contacting accelerometer for gravity wave antenna    D. Blair, J. Mills and R. Rand Summary: This paper discusses the applications of an X-band superconducting re-entrant cavity to the construction of a non-contacting accelerometer for use with a high sensitivity Weber-type gravitational radiation detector. The need for a noncontacting accelerometer for use with extremely high Q antennae is discussed. Measurement of the electrical Q of the niobium re-entrant cavity at 4.2K are presented. Finally a method is described for controlling the relative positions of the antenna and the accelerometer.         Application of superconducting magnetometers to the measurement of the vector magnetocardiogram    J. Wikswo and W. Fairbank Summary: A differential magnetometer, a molypermalloy magnetic shield, and a digital data acquisition system have been developed for detailed analysis of the human vector magnetocardiogram (VMCG). With this system, the VMCG can be recorded at any desired point around the subject's thorax while simultaneously recording the vector electrocardiogram (VECG). To simplify analysis of the three-dimensional time dependent vector magnetic field, the spatial variation of the VMCG can be described in terms of the field produced by an effective source such as a magnetic multipole series. We find the VMCG field from normal subjects to be sufficiently dipolar that a magnetic dipole alone can be used to describe the major features of the VMCG. A partial inversion of the dipole field equations and numerical analysis techniques are used to determine the components and location of the dipole that provides the least-squares fit of the dipole fields to the observed ones.         Application of SQUID magnetometer to nuclear magnetic thermometry    L. Moberly and O. Symko Summary: This paper presents an application of a SQUID magnetometer for low temperature thermometry using the magnetic properties of a nuclear paramagnet. The static magnetization of a material which obeys Curie's law provides a very sensitive means of thermometry. Also included in the device is the capability to observe, also with a SQUID magnetometer, the nuclear spin-lattice relaxation time /spl tau//sub 1/using NMR methods. This allows a temperature self-calibration of the thermometer system. As an example of a suitable nuclear paramagnet, magnetization and relaxation time data are presented for aluminum.         Advances in the use of SQUIDs for RF attenuation measurement    N. Frederick, D. Sullivan and R. Adair Summary: The SQUID system for rf attenuation measurement has been advanced by a number of significant changes. A redesign of the L-band SQUID has resulted in a significantly simpler geometry which provides an adjustable coupling for precise matching to the electronics. The redesigned SQUID contains a permanently adjusted point contact in a replaceable cartridge. Attenuation measurement with this system relies heavily on proper signal processing in the room temperature components and a careful study of these conditions indicates a series of areas where error can be generated. These signal handling problems and appropriate solutions are discussed in detail.         Application of a SQUID for monitoring magnetic response of the human brain    D. Brenner, L. Kaufman and S. Williamson Summary: Noise characteristics are reported for a SQUID system which is sufficiently sensitive to detect visually evoked magnetic fields of the human brain without shielding. Discrimination against the much larger ambient background fields is obtained through use of a flux transporter with detection coils in the form of a second order gradiometer. The continuous spectrum of noise, coherent noise at isolated frequencies, and transient noise features are described. Examples of the spatial variation of the evoked neuromagnetic field are given with emphasis on those aspects which are important considerations in the design of effective detection systems.         An offset temperature coefficient in SQUID sensors    J. Opfer and J. Pierce Summary: Output offsets in SQUID sensors which accompany changes in the sensor temperature have been measured under varying conditions of magnetic stress applied to the sensor films. It is shown that there is an offset temperature coefficient (OTC), characterizing a reversible variation of the offset with temperature, which depends upon magnetic stress. Further, the variations of the OTC with magnetic stress are shown to be reversible for stress values below a critical value. Above this critical value, an irreversible change in the OTC occurs. This change can be annealed out by heating the sensor above its critical temperature. Two mechanisms which are capable of producing an OTC which behaves in this manner are discussed in quantitative terms. One mechanism involves temperature dependent pinning forces and the other involves the temperature dependent shielding currents which flow in response to magnetic stress. A simple technique for minimizing the deleterious effects of the OTC on magnetic measurements is described.         Thin-film DC SQUID gradiometer    M. Ketchen, W. Goubau, J. Clarke and G. Donaldson Summary: A thin-film dc SQUID gradiometer has been fabricated on a single planar substrate. The superconducting pick-up loops consist of a lead strip in the form of a 48 X 16 mm rectangle with a niobium strip bisecting the rectangle. A tunnel junction dc SQUID is symmetrically located on the niobium strip. If there is a spatial gradient in the magnetic field applied to the gradiometer so that the magnetic fluxes threading the two pick-up loops differ, a supercurrent is induced in the niobium strip that is detected by the SQUID. The noise power spectrum of the SQUID is white down to a frequency of about 5x10/sup -2/Hz with a rms flux noise of 8x10/sup -5//spl phi//sub o/Hz/sup -1/2/, corresponding to a gradient sensitivity of 2x10/sup -10/G cm/sup -1/Hz/sup -1/2/.         A high accuracy gyroscope readout test facility for the relativity gyroscope experiment    B. Cabrera and F. van Kaan Summary: We are building an apparatus for Earth-based testing of a gyroscope system to be used in a satellite test of general relativity. The immediate goal is a readout capable of measuring the direction of the gyroscope spin axis to an angular resolution of one arcsecond over a limited range. A combination of SQUID magnetometers and persistent current loops are used to measure the London moment of the spinning superconducting rotor levitated electrostatically. To obtain a trapped flux signal in the gyroscope sufficiently smaller than the London moment signal, the apparatus makes use of a new magnetic field shielding technique for obtaining large superconductor shielded regions below 10/sup -7/gauss.         A high accuracy all-angle gyroscope readout using quantized flux    J. Anderson and C. Everitt Summary: Means are described to use SQUID magnetometer flux counting and the London moment of a spherical, superconducting gyroscope to read out the gyroscope spin axis direction to an accuracy of at least 23 bits per quadrant. The system is discussed in analogy to optical fringe counting as applied to distance measurement. Several methods of applying both analog and digital SQUID magnetometers to the readout problem are given, as well as limitations on each. Described are two methods of increasing the flux available for measurement: magnetizing the gyroscope with a trapped field, and optimizing readout circuit inductances. Finally, the same principle on which the gyroscope readout is based is applied to a description of a high accuracy, flux counting, digital angle encoder.         Analog computer studies of frequency multiplication and mixing with the Josephson junction    A. Risley, E. Johnson and C. Hamilton Summary: Using a point-contact Josephson junction (JJ), direct frequency measurement of far-IR laser lines can be performed by mixing the Nth harmonic of a microwave frequency /spl upsi//sub 2/with the laser frequency /spl upsi//sub 1/to produce a beat signal /spl upsi//sub IF/such that /spl upsi//sub IF/= /spl upsi//sub 1/- N/spl upsi//sub 2/. Analog computer simulation of the JJ has revealed an efficient mode of frequency multiplication and mixing. This is a condition wherein the self oscillation, /spl upsi//sub J/, is phase locked to a frequency /spl upsi//sub J/= /spl plusmn/ /spl ell//spl upsi//sub 2//spl plusmn/ k/spl upsi//sub 1//spl plusmn/ m /spl upsi//sub IF/where /spl ell/, k, and m are integers. The analog studies show that this phase locking can occur at very low as well as at high levels of the external drives. The result of the phase lock is an efficient transfer of energy into the /spl upsi//sub IF/output signal. At least one experimental result has verified the occurrence of phase locking to difference frequencies. It is also well known that the optimum bias points in mixing lie between the /spl upsi//sub 2/steps. The interpretation of these results and the direct role played by /spl upsi//sub J/in mixing experiments has not, however, been generally recognized.         Coupling at RF frequencies in the superconducting film transformer    A. Fiory Summary: Two superconducting oxygen-doped aluminum films, separated by a silicon monoxide insulating film, contain two magnetically coupled vortex lattices in a transverse applied magnetic field. The rf impedance of the device shows structure that is sensitive to details of the magnetic coupling force, which is a periodic function of the relative displacement of the two vortex lattices. When the lattices are driven at nearly equal dc velocities, the observed rf response is a function of the coupling force, itself externally controlled by the dc currents applied to the films. Rf measurements were used to obtain the relaxation time of the coupling mechanism, which is inversely proportional to the gradient of the coupling force. By integration, one obtains the displacement dependence of the coupling force. Results of a recent theory by Clem are in good agreement with the data.         Millimeter wave behavior of superconducting point contact SQUID    H. Kanter and F. Vernon Jr. Summary: A superconducting point contact waveguide SQUID has been operated at 89 GHz. The performance is qualitatively the same as at lower frequencies in agreement with the SQUID model. With the Nb point located across a 0.15 mm high E band waveguide, reflection coefficient measurements were made as a function of both supercurrent phase as controlled by an externally applied magnetic field and millimeter wave power. Large parametric reactance variations were produced by changing the supercurrent phase. As the millimeter wave power is increased flux cycling was observed which involved up to four steps. This behavior corresponds to a flux transition time less than 10-/sup 12/sec. Implications of the cos /spl phi/ term and negative resistance effects in the observed behavior of the reflection coefficient will be discussed.         Microwave phenomena in thin- film Josephson junctions coupled to a contiguous microstrip resonator    T. Finnegan, L. Holdeman and S. Wahlsten Summary: A half-wavelength microstrip resonator has been used to couple microwave radiation between Josephson junctions and an external 50 /spl Omega/ transmission line, and various microwave properties of these resonator-coupled junction devices have been studied. The advantages of these devices in applications including coherent radiation emission, 2e/h precision voltage sources, and parametric plasma-related effects are described.         Can superconductivity contribute to the determination of the absolute ampere?    D. Sullivan and N. Frederick Summary: The absolute ampere is shown to be derivable from a static levitation of a superconducting mass. The magnetic force which balances the gravitational force can be obtained from a combination of inductance and linear position measurements. A unique feature of the concept is the use of the calculable capacitor for the inductance measurements. Besides the possibility of this specific approach other concepts involving superconductivity are also discussed.         The 35 m superconducting cable test facility    G. Bogner, P. Penczynski and F. Schmidt Summary: To demonstrate the technical feasibility and capability of superconducting ac cables a 35 m long ac single phase test cable for 110 kV and 10 kA is under construction at present. The rigid cryogenic envelope has already been assembled. Good experience was gained with the applied mounting technique which is described. Wires consisting of a high purity Al-core enclosed by a thin layer of Nb are used as cable conductors. They were fabricated in lengths of several thousand meters under large scale conditions and exhibited excellent electrical behaviour. After manufacturing some dummies with pure Al-wires, a 50 m long originally sized flexible cable core consisting of superconducting wires and wrapped HDPE tape insulation was fabricated on conventional cable machinery in our cable works. Dielectric measurements at 4.2 K and 2.5 bar on originally sized and large scale fabricated cable core pieces yielded breakdown voltages, partial discharge inception voltages and dissipation factors which are compatible with cable standards. Two one phase 110 kV - 10 kA cable terminations have been constructed and tested. They showed satisfying behaviour with respect to stress and current loads.         Studies of helical conductor models for superconducting AC power transmission    M. Garber, T. Barber and G. Morgan Summary: In the BNL concept of a superconducting ac power transmission cable the conductors are made of Nb/sub 3/Sn tapes wound helically on cylinders. Recently, it was decided to make each conductor in the form of a double layer winding in which the layers are of opposite helicity. This reduces undesirable consequences of axial flux generation. After reviewing the considerations which lead to the double helix conductor, experiments with short models (0.8 m long) are described. Results are given for ac loss and quench current measurements. Quench currents in excess of 3400 A/cm rms have been obtained. Ac losses are higher than those of short samples of the tapes used but are acceptable. Loss calculations for the double helix configuration are discussed.         Asymmetry of thermal propagation velocity in a long force-cooled superconducting test line    J. Hoffer, E. Kerr and W. Overton Jr. Summary: We have observed the phenomenon of thermal destruction of superconductivity by current in a force-cooled test model power transmission line of 20 m length at currents up to 9 kA and temperatures between 8 K and 14 K. This line, fabricated by soldering doubly-stabilized Nb/sub 3/Sn tapes to each side of a bar of 0fhc copper (0.3cm X 1.58 cm), was enclosed in a German silver cryogen flow tube. The cryogen (He gas) was controlled at a flow rate of 0.5 to 0.7 gm/sec. Destruction was initiated by application of a short duration heating pulse to a small section of line. The velocity of N-S interface zone propagation was measured over 1.0 m test sections located downstream and upstream from the initial section. The upstream moving zone is always in a nearly-constant-temperature cryogenic environment. However, downstream portions contact an environment preheated by Joule heating in upstream normal N zones and thus transfer less heat and exhibit a much higher velocity. This qualitative explanation of the observed dramatic velocity asymmetry is to be supplemented by a more precise description of the physics of the moving N-S interface which must include a proper model for the heat conductance into the cryogen. Various models for heat conductance can be tested in velocity calculations.         Thermal acoustic oscillations in current leads cooled with supercritical helium    D. Daney, P. Ludtke and M. Jones Summary: Observations are reported of pressure oscillations in model current leads cooled with supercritical helium. The oscillations are characterized and regions of the independent parameters in which the oscillations occurred are given. Different behavior depending on the design of each lead is noted. The effects of the thermodynamic state of the helium and the hydraulic diameter of each lead are in agreement with the theoretical predictions for simple tubes.         Linde superconducting cable system projected performance and costs    F. Notaro, A. Acharya and W. BeVier Summary: The design of a superconducting 3400 MVA, 138 KV, 3/spl phi/, ac power transmission system has been defined in sufficient detail to permit a realistic appraisal of performance and costs to be established. This paper describes the present state of this system and presents the estimated costs for its fabrication, installation and operation.         Development of Nb/sub 3/Sn tapes having low AC losses    P. Brisbin, W. Markiewicz, R. Wilcox and C. Rosner Summary: A process has been developed for modifying the surface topography of Nb/sub 3/Sn tapes produced by the diffusion process such that losses at 60 Hz and 4.2 K are reduced by a factor of 4 or more. The process comprises an etching sequence followed by reapplication of tin; the latter operation restores solderability for the subsequent fabrication of laminated conductor and, under some conditions, contributes to the reduction of ac losses. The treated superconductor tapes apparently fulfill the essential requirements established for superconducting ac power transmission cables.         Fabrication and properties of Nb/sub 3/Sn tapes by the "Bronze process" application to superconducting power transmission lines    E. Adam, P. Beischer, W. Marancik and M. Young Summary: Long lengths of Nb/sub 3/Sn tapes have been prepared by extrusion and rolling of bronze clad niobium billets. Fine grained layers up to 5 /spl mu/m thick, were formed by heat treating at 750/spl deg/C for several hours. By combining the "bronze-process" with an external Sn diffusion technique layers up to 15 /spl mu/m thick were produced. Loss data at 60 Hz are given for various configurations with and without copper stabilizing layers. DC critical current densities are also given.         Temperature dependence of AC losses in CVD-prepared Nb/sub 3/Ge    J. Thompson, M. Maley and L. Newkirk Summary: Hysteretic losses have been measured as a function of temperature from 4 to 20 K in bulk samples of CVD prepared Nb/sub 3/Ge. The measurements have been performed on samples which contained differing amounts of second phase Nb/sub 2/Ge/sub 3/and which have been subjected to various surface treatments. Losses at 50 Hz and 500 rms A/cm have been determined to be as low as 0.2 /spl mu/W/cm/sup 2/at 4 K and 12.7 /spl mu/W/cm/sup 2/at 12 K in samples containing a small per cent of second phase and whose surfaces have been both mechanically polished and chemically etched. From measurements of the hysteretic power loss, the temperature dependence of the critical current density J/sub c/(T) can be determined by assuming a Bean-London type critical state model in the high current regime. It is found that J/sub c/(T) = J/sub c/(0)[1-(T/T*/sub c/)/sup 2/] best describes the data over the range 4 K to T/sub c/*. At low values of induced current, substantial surface shielding /spl utri//spl sigma/ is observed in samples which have been polished and etched. /spl utri//spl sigma/ has been measured to be as large as 450 rms A/cm at 4.0 K.         AC losses of internally deposited Nb/sub 3/Ge films    K. Kim, Y. Kim, J. Savage and L. Newkirk Summary: Nb/sub 3/Ge films deposited on the inside of a copper tube have been measured. The tubular sample was modified into a tape sample for measuring purposes. The total ac losses contain the substrate loss as well as the superconductor loss, and by varying the frequency and the field the two are separated. The plot of the loss vs. the surface roughness indicates that the losses in this case are dominated by the superconducting diffusion layer. The problem presented by the diffusion layer in any partially coated tape is stressed.         AC loss and DC critical current densities of Nb/sub 3/Sn tapes by the solid state diffusion process    M. Suenaga, C. Klamut and J. Bussiere Summary: The effects of metallurgical processing on 60 Hz ac losses and dc critical currents in Nb/sub 3/Sn tapes fabricated by the solid state diffusion technique were investigated. An addition of Al to the Cu-Sn alloy for the matrix resulted in large reduction in the ac losses of Nb/sub 3/Sn tapes, but the highest linear critical current densities were observed in Nb/sub 3/Sn tapes produced with a Nb-1 wt% Zr core in a Cu-13 wt% Sn matrix. Values of the losses and the critical currents in these tapes can meet the present requirements for the ac superconducting power cables.         Stabilization of superconductors for use in magnets    M. Wilson Summary: There are two main causes of degraded performance in superconducting magnets, magnetic instability or flux jumping and mechanical instability. Cryostatically stabilized conductors are able to cope with both kinds of instability but finely subdivided conductors are only stable against flux jumping. It is suggested that the inclusion of a small proportion of helium in the magnet windings could provide sufficient transient stability to enable finely subdivided conductors to work well in the presence of mechanical instabilities.         Multifilament Nb/sub 3/Sn conductors: Progress and prospects    D. Deis Summary: Multifilament Nb/sub 3/Sn conductors are now at the stage where several coils have been constructed and various types of material are available commercially from several suppliers. Even so, some questions remain with regard to the reliable use of this material, particularly in large-scale systems. The initial portion of this paper covers the main features of past work as they relate to the present situation. In the latter part, those areas where major uncertainties remain are described along with current projected work in these areas.         Development of multifilamentary Nb/sub 3/Sn conductors for fusion research    D. Cornish, D. Deis, R. Nelson, R. Scanlan, C. Taylor, R. Vandervoort, F. Wittmayer and J. Zbasnik Summary: A program at Lawrence Livermore Laboratory to develop multifilamentary Nb/sub 3/Sn conductors suitable for use in constructing fusion research magnets has resulted in the commercial production of conductors having cross-sectional areas in the range 0.06 cm/sup 2/to 0.84 cm/sup 2/. Critical current densities near the goal of 10/sup 4/A/cm/sup 2/at 12 T and 4.2 K have been obtained in conductors produced by two different techniques. The latest results of this program are presented and discussed.         Advanced conductor configurations for large magnets    E. Adam, J. Dickson, E. Gregory, W. Marancik and S. Poulsen Summary: Various configurations of NbTi and Nb/sub 3/Sn superconductors are of potential value for a large number of applications involving both dc and pulsed fields. The great diversity of superconductor magnet designs has required the development of a broad range of new conductor configurations. In design of conductors several objectives must be considered including stability, mechanical strength, cost and ease of handling. These objectives can be met through the use of monoliths, special sheathing, mixed matrices, cables, braids and combinations of these. Such combinations can be constructed to more closely match the required specifications than may be possible by using only one technique.         The influence of tensile stress on the critical current of filamentary Nb/sub 3/Sn magnet conductor    D. Larbalestier, J. Magraw and M. Wilson Summary: The design and construction of an experiment to measure the influence of tensile stress on the critical current properties of filamentary Nb/sub 3/Sn composites is described. Special attention has been paid to obtaining design data useful for coil construction. The results obtained for one type of composite show that the critical current is reduced by tensile stress. At stresses up to 240-250MN/m/sup 2/(/spl epsiv/~ 0.5%) the effect is reversible, being about 5-10% of the original critical current. Beyond this level permanent degradation occurs. The deterioration is progressive rather than catastrophic. The implications for magnet construction are discussed.         Studies on filamentary Nb/sub 3/Sn wires fabricated by the infiltration method    K. Hemachalam and M. Pickus Summary: Superconducting wires containing a network, of Nb/sub 3/Sn filaments are produced by powder metallurgy techniques. The fabrication involves achieving a controlled porosity in compacts of sintered niobium followed by tin infiltration and mechanical reduction. The Nb/sub 3/Sn filaments, typically 1-5 /spl mu/m in size, are formed by a short heat treatment. The effects of heat treatment on critical current and transition temperature are presented for reaction temperatures in the range of 700-1200/spl deg/C and for lengths of time varying from 1 min to several hours. The dependence of J/sub c/on filament size is studied. The conductor evaluation includes measurements of T/sub c/, of J/sub c/up to 170 kG, and mechanical bend tests. Efforts are made to explain the results, wherever possible, by means of microstructural observations such as the Nb/sub 3/Sn grain size and the microvoids formed as a result of diffusion treatment. In view of the high values of J/sub c/obtained- 1.1x10/sup 5/A/cm/sup 2/at 100 kG and 7.5x10/sup 4/A/cm/sup 2/at 150 kG (computed on the basis of the Nb/sub 3/Sn-Nb core)-these filamentary wires appear to have a potential especially for applications in high field superconducting magnets.         Multifilament V/sub 3/Ga and Nb/sub 3/Sn superconductors produced by the ECN-technique    J. Elen, C. van Beijnen and C. van der Klein Summary: Multifilament V/sub 3/Ga and Nb/sub 3/Sn have been produced using the ECN-technique. Composites of vanadium or niobium tubes, containing a powder of intermetallic compounds and embedded in pure unalloyed copper are reduced to wires of 1-0.5 mm diameter. V/sub 3/Ga is formed at reaction temperatures between 550/spl deg/C and 650/spl deg/C and Nb/sub 3/Sn between 600/spl deg/C and 700/spl deg/C. During the isothermal heat treatments intermediate formation of V/sub 6/Ga/sub 2/and Nb/sub 6/Sn/sub 2/occurs. T/sub c/values increase during progression of the reactions from 10 K to 15 K for V/sub 3/Ga and from 14 K to 18 K for Nb/sub 3/Sn. The J/sub c/(H) curves between 2 T and 11 T for V/sub 3/Ga show that the field dependence is strongly related to the degree of chemical reaction. After complete formation of the V/sub 3/Ga layer the decay of the almost exponential J/sub c/(H) curves is weakest, indicating that these samples are superior at higher field values, in spite of lower values at low fields. The J/sub c/values at 10 T of completely reacted V/sub 3/Ga samples are found to be strongly dependent on layer thickness, ranging from 1x10/sup 8/A/m/sup 2/for a layer of 12 /spl mu/m to 7x10/sup 8/A/m/sup 2/for a layer of 6 /spl mu/m.         Critical current and temperature of filamentary niobium tin as a function of reaction conditions    A. Mortis and I. McDougall Summary: The critical temperature of filamentary niobium tin as determined by reaction conditions has been measured along with critical current as a function of field at different temperatures in the range 4.2 to 18/spl deg/K. Using diffusion couples able to provide compound of less than stoichiometric amounts of tin, a minimum in Tc and a maximum in Jc has been established and it is shown that the optimum reaction depends on the operating temperature of the composite. A hypothesis is advanced explaining results in terms of changes in the position of niobium and copper in the compound lattice.         An improved method for fabrication of Nb/sub 3/(Al,Ge) wire    K. Togano and R. Rose Summary: Technologies for fabrication of Nb/sub 3/(Al/sub .75/Ge/sub .25/) wire by reaction of mechanically fabricated composites of Nb, Al and Ge have had very limited success due to the lack of plasticity of elemental Ge, which leads to gross compositional inhomogeneity and low transition temperatures. However, it is possible to develop considerable ductility in Al-Ge alloys, and by using such alloys composited with Nb, composites may be mechanically fabricated which, when reacted in wire form, have transition temperatures ca. 20/spl deg/K. Due to the nature of the ternary phase diagram, such transition temperatures may be achieved for all core compositions between Al- 14% Ge and Al-30% Ge. However, high reaction temperatures, ca. 1800/spl deg/C, are necessary, which suggests low-temperature stability problems with the A15 phase which are similar to those in the binary Nb-Al system.         Metallurgy, fabrication, and superconducting properties of multifilamentary Nb/sub 3/Al composites    J. Hafstrom Summary: The control of metallurgical structure during fabrication that will improve the superconducting properties of multifilamentary, aluminium-stabilized, Nb/sub 3/Al composites is described. Composites are fabricated by placing niobium rods in an aluminum matrix, and then drawing to wire. Nb/sub 3/Al is formed at temperatures exceeding 1800/spl deg/C for /spl sim/5 s and ordered at 750/spl deg/C for 48 h. A critical current, J/sub c/(H), in excess of 10/sup 5/A/cm/sup 2/(F/sub p/ /spl sim/ 7 /spl times/ 10/sup 8/ dynes/cm/sup 3/) at 7 T and a T/sub c/to 18.2 K are obtained. Attempts to improve J/sub c/(H) by controlling the grain size in the Nb/sub 3/Al diffused layer are discussed. Precipitates, arising from the addition of carbon during Nb/sub 3/Al layer growth, do not appear to be effective as grain-boundary or flux pinners. When 1% Zr is added to the Nb, the growth of the Nb/sub 3/Al layer is accelerated, T/sub c/is lowered and J/sub c/(H) is not significantly improved. J/sub c/(H) rapidly decreases with an increase in Nb/sub 3/Al or (Nb-Zr)/sub 3/Al layer thickness, d. J/sub c/(H) is independent of d in composites with d /spl gsim/ 1.5 /spl mu/m. In general, the Nb/sub 3/Al grain size appears comparable to d for d /spl les/ 1 /spl mu/m. Significant improvement of J/sub c/(H) for Nb/sub 3/Al superconducting composites reacted at temperatures above 1800/spl deg/C (to achieve T/sub c/> 17 K) is achieved only by maintaining the layer thickness well below d /spl sim/ 1.0 /spl mu/m.         Preparation of continuous, superconducting and high strength Nb/sub 3/Ge composite filament    I. Ahmad, W. Heffernan and D. Gubser Summary: A chemical vapor deposition process for the preparation of continuous, high strength and flexible Nb/sub 3/Ge/Nb/W-1% ThO/sub 2/filament and preliminary observation of its superconducting behavior are described.         Results of the Fermilab wire production program    B. Strauss, R. Remsbottom, P. Reardon, C. Curtis and W. McDonald Summary: In the Spring of 1974 the commercial wire business has reached a low ebb and continues supply by multiple sources was not encouraging. Fermilab, then just starting on its Energy Doubler program, was face with the problem of maintaining multiple sources of supple as well as a number of technical problems in obtaining the high critical current densities required for the dipole magnets. To alleviate these problems it was decided to embark on a multifaceted program to provide a usable high production method of fabricating multifilamet composite superconductor.         Superconducting Nb/sub 3/Sn cavities with high microwave qualities    B. Hillenbrand, H. Martens, H. Pfister, K. Schnitzke and Y. Uzel Summary: As the lower critical flux density B/sub c1/apparently presents no limit for microwave superconductivity, Type II superconductors with a high transition temperature offer advantages over niobium, the material normally used for superconducting cavities. We have developed Nb/sub 3/Sn cavities by exposing a Nb structure to a saturated tin vapour atmosphere at about 1000/spl deg/C. A report is given on the preparation of smooth and homogeneous Nb/sub 3/Sn layers and on measurements on X-band cavities. At 4.2 K, Q-values up to 2.7x10/sup 9/have been measured which are higher by a factor of seventy than for Nb resonators at the same temperature. Critical flux densities of 89 mT at 4.2 K and 106 mT at 1.5 K have been reached. With Nb/sub 3/Sn cavities of this kind it would for the first time appear to be possible to operate superconducting cavities for technical applications at a temperature of 4.2 K. This would offer Considerable advantages.         On properties of superconducting Nb/sub 3/Sn used as coatings in RF cavities    P. Kneisel, H. Kupfer, W. Schwarz, O. Stoltz and J. Halbritter Summary: Nb/sub 3/Sn layers of several /spl mu/m thickness on bulk niobium have been prepared by heating the niobium samples in a saturated tin vapor at 1050/spl deg/c. The layers have been analyzed by scanning electron microscopy and electron microprobe analysis; furthermore, measurements of penetration depth /spl lambda/(T), pinning, critical field B/sub c2/(T), rf surface resistance R(T) and rf peak field have been carried out. As a result /spl lambda/(T=0) /spl sime/ 170 nm, Ginzburg-Landau parameter /spl kappa/ /spl simq/ 18, London penetration depth /spl lambda//sub L/= 40 nm, coherence length /spl xi//sub F/= 40 nm and mean free path /spl ell/ = 2 nm have been found by using the values 2/spl mu//kT/sub c/= 4.2 and B/sub c/(0) = 0.54T. These material parameters - in connection with weak flux pinning - indicate quite homogeneous Nb/sub 3/Sn layers. With the cavity measurements a surface resistance R/sub res/(3 GHz) = 1.7 . 10/sup -7/Ohm could be achieved; the highest observed electric surface field so far was E/sub max/,surf. = 14 MV/m. The apparently good quality of the Nb/sub 3/Sn oxide interface is indicated by the BCS like /spl lambda/(T)-dependence and the comparably weak electron loading of Nb/sub 3/Sn cavities.         Measurement on a Nb/sub 3/Sn structure for linear accelerator application    G. Arnolds and D. Proch Summary: A three cell 8 GHz accelerator structure fabricated from bulk niobium, was processed in a tin vapor atmosphere at 1050/spl deg/C. The structure was operated in a /spl pi//2 standing wave mode. At 4.2 K a surface resistance of 1.1 /spl mu//spl Omega/ and an accelerating field of 2.7 MV/m was obtained. This corresponds to peak surface fields of E = 10 MV/m and B = 20 mT. The fields were limited by fast magnetic thermal breakdowns. The temperature dependence of the rf surface resistance yielded a transition temperature of T/sub c/= (18.0 /spl plusmn/ 0.2)K and an energy gap of 2/spl utri/ (0) = (4.6 /spl plusmn/ 0.2)kT/sub c/.         Frequency modulated superconducting resonators    H. Yen, G. Dick and J. Mercereau Summary: High Q superconducting resonators whose resonant frequencies can be mechanically modulated over a wide range at a rapid rate have been developed. In the few hundred megahertz range, frequency modulation (FM) of these resonators by nearly a factor of three has been achieved at modulation rates up to two kilohertz. Mechanical techniques for producing large FM are being developed in order to achieve efficient electromechanical energy conversion in these devices. This paper reports analyses and experiments on the time evolution of stored electromagnetic energy under adiabatic FM conditions. The behavior of coupled FM superconducting resonators as a microwave switch is also illustrated by computer simulation. Application of the coupled FM resonators to the generation of very high power microwave pulses is discussed.         Progress on the superconducting RF-particle separator for CERN    A. Citron, G. Dammertz, M. Grundner, L. Husson, P. Kneisel, H. Lengeler and E. Rathgeber Summary: The status of the deflectors for the superconducting rf separator is given. The design values for the Q-factor (Qo = 5.10/sup 8/) and the deflection field (E/sub o/= 2 MV/m) have been reached in two combined 60 cm sections. During a 430 h run at design field no deterioration of Q/sub o/and E/sub o/was observed. In a first measurement with a full deflector assembled from 5 sections (10/sup 4/cells) Q/sub o/= 9.10/sup 8/and E/sub o/= 1.2 MV/m corresponding to a peak magnetic field of 19 mT have been reached.         The split-loop resonator as a superconducting heavy ion accelerating element    G. Dick and G. Sprouse Summary: Ion acceleration tests utilizing a superconducting split-loop resonator at accelerating potentials above 2.7 MV/m have been made on ions up to mass 29 and charge state 12. The velocity acceptance and transit time effects were measured and found to be in good agreement with theoretical estimates. Because of the very low energy content of this resonator, the rf power dissipation at low /spl beta/ is less than 10% of an equivalent reentrant cavity design thus relaxing requirements on the superconducting surface resistance and on the phase stabilizing system.         Tests of a niobium split-ring superconducting heavy-ion accelerating structure    R. Benaroya, L. Bollinger, A. Jaffey, T. Khoe, M. Olesen, C. Scheibelhut, K. Shepard and W. Wesolowski Summary: A niobium split-ring accelerating structure designed for use in the Argonne superconducting heavy-ion energy booster has been successfully tested. The superconducting resonator has a resonant frequency of 97 MHz and an optimum particle velocity /spl beta/ = 0.11. Ultimate performance is expected to be limited by peak surface fields, which in this structure are 4.7 E/sub a/electric and 170 E/sub a/(Gauss) magnetic, where E/sub a/is the effective accelerating gradient in MV/m. RF losses in two demountable superconducting joints severely limited performance in initial tests. Following independent measurements of the rf loss properties of several types of demountable joints, one demountable joint was eliminated and the other modified. Subsequently, the resonator could be operated continuously at E/sub a/= 3.6 MV/m (corresponding to an energy gain of 1.3 MeV per charge) with 10w rf input power. Maximum field level was limited by electron loading. The mechanical stability of the resonator under operating conditions is excellent: vibration induced eigenfrequency noise is less than 120 Hz peak to peak, and the radiation pressure induced frequency shift is /spl utri/f/f = 1.6x10/sup -6/E/sub a//sup 2/.         Beam tests and phase locking of superconducting cavities for heavy ion linac    P. Ceperley, H. Glavish, S. Hanna, M. Samuel and J. Sokolowski Summary: This paper describes our progress in two important aspects of the development of a superconducting heavy ion linear accelerator: phase locking and bunching. This accelerator is based on a 430 MHz niobium reentrant cavity developed at Stanford. A compact electronic package has been developed to perform for each cavity the function of phase locking, as well as, supplying RF power, controlling cavity fields, and controlling the frequency tuners. Frequency tuning of the cavities was accomplished by use of two tuners per cavity, a coarse, motor-driven tuner and a fine piezoelectric one. The coarse tuner (2 MHz range) was initially operated to bring the frequencies of the cavities within the range of a few hundred hertz of each other. The fine one was continuously operated to automatically correct for small frequency differences. Large frequency changes were prevented by stabilizing the pressure of the dewar. The tuning and pressure stabilization allowed us to keep the frequency differences within 20 Hz. Further stabilization and phase locking will require damping of the acoustical modes of the dewar. The bunching capability of the superconducting cavities was demonstrated using a 2 MeV proton beam from a Van de Graaff accelerator. More than 43% of the beam was compressed into 250 psec bunches which would be suitable for the proposed accelerator. The practicality of these cavities in an operating accelerator was shown by their dependable operation for a few months, on and off, during these tests, even with minor vacuum failures.         AC-losses in multifilamentary superconductors at technical frequencies    G. Ries Summary: Multifilamentary superconductors exposed to an alternating field of small amplitude but in the technical frequency range as in a rotor of a superconducting generator show a characteristic dependence of losses on frequency. Shielding of the conductor by the induced currents is shown to be relevant. In a twisted cylindrical multifilamentary conductor the shielding currents are calculated and formulas for the hysteretic loss and eddy current loss are given as function of frequency and time constant /spl tau/ of the conductor. It is shown, that a long twist length can give lower losses than a short one.         Losses of multifilamentary superconductors with ordinary and alternating twist    K. Jungst and G. Ries Summary: As has been shown in previous papers the twist of multifilamentary superconductors gives rise to new coupling losses when the conductor is exposed to pulsed longitudinal magnetic fields. These losses can increase the total conductor losses considerably. For a loss reduction an alternating twist has been proposed by the authors. First conductor samples with alternating twist have been manufactured and magnetization experiments have been performed. The losses of such samples in longitudinal fields show reduced values compared to samples with ordinary twist, in good agreement with the theoretical predictions.         Anomalous increments of AC losses due to flux jumps    F. Irie, G. Klipping, K. Luders, T. Matsushita, U. Ruppert and M. Takeo Summary: AC losses are measured applying magnetic fields of frequencies from 8.6 to 75 Hz and of 3 kG peak values to wires of Nb-60.2Ti-2.8Zr alloy mounted in slots of a bakelite bobbin. The temperature is varied between 1.9 K and the superconducting transition temperature T/sub c/= 8.9 K using supercritical He as coolant for the higher temperature region. Anomalous increments of AC losses caused by flux jumps are observed at certain field values H/sub fj/. H/sub fj/is almost constant at temperatures T = 4.2 to 6 K and decreases if the temperature is reduced below 4.2 K. The temperature dependence of H/sub fj/can be explained qualitatively by the temperature depencence of both the specific heat and the pinning force of the sample. The quantitative difference as well as a very weak frequency dependence of H/sub fj/and a reduction of H/sub fj/by embedding the sample in grease may be due to the influence of the special heat transfer conditions.         Experimental simulation of pulsed field losses in tokamak toroidal field coils    J. Miller and S. Shen Summary: Experiments have been carried out to measure loss in a twisted multifilamentary composite superconductor when exposed to a transient longitudinal field. We investigate the variation of losses both as a function of transverse applied field and of sample transport current. Losses are probed mainly by measurement of the dynamic resistivity of the sample during the longitudinal pulse. Experimental results are compared with theories 1,2,5,6,8 for the zero transport current case. The extension of theory to include transport current is also discussed, and the impact on tokamak toroidal field coil design is considered.         Design and use of an electronic loss measurement apparatus for superconducting coils    E. Lucas, W. Punchard, P. Margosian and D. Beard Summary: A description is given of an apparatus that makes use of an electronic technique for measuring losses in rapidly pulsed superconducting coils. Data taken with this apparatus on a coil having an energy storage capability of approximately 7 kJ is presented. The apparatus described is essentially an electronic wattmeter. It makes use of a magnetically coupled coil to cancel out as nearly as possible the inductive portion of the coil voltage during charge and discharge, thus leaving a voltage which is due almost entirely to the coil energy losses. This voltage is then integrated and displayed along the vertical axis of an X-Y oscilloscope, the horizontal axis being the coil current. The area of the figure so formed is proportional to the energy dissipated during the cycle. Two different techniques for sensing the inductive component of the coil voltage are described together with data taken by each technique. Data are presented for full cycle hysteresis loops at frequencies of 11.7, 16.2, and 26.2 Hz and for half cycle hysteresis loop at discharge rates of 54 and 348 amperes per second and several charge rates. These data show the coil losses to be higher than those predicted by a simplified theory taking into account magnetization losses only.         60 Hz AC losses in superconducting solenoids    W. Lee and J. Broach Summary: Loss measurements have been made on inductively wound superconducting solenoids using a flowmeter-type measuring system. The solenoids were wound from representative samples of commercially available Nb-Ti multifilament wire and were powered by a variable voltage 60 Hz line source. Losses have been found to vary with the nth power of the exciting current where 3 /spl lsim/ n /spl lsim/ 4. Loss rates of 0.2 W per cm/sup 3/of conductor at 4 A, peak excitation, are typical for the samples measured.         Energy losses in mixed matrix superconducting wires under fast pulsed conditions    J. Wollan Summary: Energy losses have been measured on a set of mixed matrix (CuNi, Cu, NbTi) superconducting wires at /spl dot/B's up to 1.5x10/sup 7/G/s. The losses have been measured as a function of wire diameter, twist pitch, maximum applied field, and /spl dot/B. Both static and dynamic losses were measured for a field applied perpendicularly to the wire axis. The dynamic losses were measured by slowly applying an external field to a sample and then causing the field to decay exponentially in roughly 1 ms to 10 ms. Under low B (9 kG) and /spl dot/B (10/sup 6/G/s) conditions the hysteretic loss dominated. At high B (21 kG) and /spl dot/B (1.5x10/sup 7/G/s) the matrix losses became dominant. The systematic variation of the losses with the mentioned parameters will be presented and will be compared to theoretical predictions.         Experimental and theoretical approach of current distributions and losses in superconducting composites for fusion magnets    B. Turck Summary: In untwisted composites, azimuthal induced currents are responsible for magnetization and losses. In twisted composites extra coupling longitudinal currents are induced, owing to the solenoidal aspect of the filaments. A model is presented which takes into account the magnetization of both origin. Expressions are proposed as functions of the amplitude of the pulsed ex - ternal field. Experimental results are in good agreement. Critical densities for induced currents are given.         Superconducting wire test    R. Yamada, H. Ishimoto and M. Price Summary: An extensive and systematic measurement on niobium-titanium superconducting wire for the Energy Saver/Doubler project has been carried out. The measured characteristics are short sample data, hysteresis loss and ac loss. The effect of field orientation on the hysteresis and ac loss of the wire was measured for both soldered and unsoldered cable. The hysteresis loss curves are found to have different characteristics depending on the field orientation. In the case of soldered cable the coupling current between the strands is confirmed to be serious, especially with the wide face perpendicular to the field. The ac loss of several small dipole magnets was also measured by using an on-line computer system, and the results are compared with calculated values based on sample wire measurement. In the ac loss measurement of these magnets we observed two breaks in the excitation curve. The one at low field is attributed to complete flux penetration into the filaments and the other at high field to wire movement.         Hysteresis losses in superconducting coil    Y. Kuwasawa, T. Ando and S. Nakano Summary: The hysteretic losses of superconducting coils are measured and the results are compared with theoretical calculations. Wires used for coils are Nb-Ti twisted ones with 19 filaments. Coupling between filaments may be negligible, because they are insulated electrically from each other. Special care is also taken for the uniformity of magnetic field of the coils. The measured dependence of hysteretic losses on the magnetic field strength of coils agrees with the theoretical one and the loss energy density is irrelevant to the geometry of the coils.         Calculation of decrease in A.C. losses in wires of type II superconductors in longitudinal magnetic fields    R. Gauthier and M. LeBlanc Summary: We present two models for calculations of A.C. losses in wires of type II superconductors in static axial fields. Both models exploit the critical state equation using F/sub p/= /spl mu//sub o//spl alpha/(T)B(1 - B/H/sub c2/). In cylindrical geometry this needs to be supplemented by an additional prescription. For one model, we assume pure axial current flow (j/spl theta/ = 0). In the other, an empirical critical orientation equation d/spl phi//dr = /spl plusmn/ k F/sub p/\cos/sup 2//spl phi//B/sup 2/is introduced to govern the angle /spl phi/ flux lines make with the z axis as they move in and out during the current cycle. The calculated curves are compared with existing data on A.C. losses at low frequencies.         Skin effect alternating current losses in multifilamentary superconductors    J. Murphy Summary: Under some circumstances, losses in superconduct, ing magnet systems can be primarily due to the transport current carried by the conductor. This type of loss is sometimes calssified as a self-field loss. This paper discusses the theory of sinusoidal alternating transport current losses in a cylindrical multifilamentary superconducting wire. Maxwell's equations have been solved for a long wire of radius R/sub 0/, twist length L and classical skin depth /spl delta/. Eddy current and hysteresis loss expressions are presented in two limits. The limits have been distinguished by the field distribution in the region of the wire which is not carrying the transport current (R /spl leq/ R/sub 1/. At low frequencies, i.e.,/spl sqrt/2 R/sub 1/ < < /spl delta/, the axial component of the magnetic field or "self field" is uniform. At high frequencies, i.e.,/spl sqrt/2 R/sub 1/ > > /spl delta/, the magnetic field in the interior is concentrated in a thin layer of the order of a skin depth in thickness. The loss expressions were determined assuming a continuum model with anisotropic conductivities for the superconductor.         Losses in multifilamentary superconductors at low levels of excitation    V. Zenkevitch and A. Romaniuk Summary: Results are presented of a theoretical analysis and experimental study of coupling losses in the matrix of twisted multifilament superconducting wires in transverse variable magnetic fields. The data obtained relate to a range of the amplitudes and rates of the field variations such that no saturation of the superconducting filaments with induced current is attained. Cases of periodic and single field pulses of different shape were analyzed to show a considerable effect of these factors upon losses. It is shown that the loss dependence upon the twist pitch and matrix resistance is different for different pulse shapes.         Losses in twisted composite superconductors in a high pulsed magnetic field    V. Zenkevich, R. Mints, V. Andrianov, V. Baev and A. Rakhmanov Summary: An experimental and theoretical study was made of losses in twisted composite superconductors in a strong pulsed magnetic field. The field amplitude reached 4.5T, and the magnetic field variation rate 2,000 T/sec. It is shown that the dependence of the specific heat release on the maximum rate of variation of the magnetic field is essentially nonmonotonic in nature. In the transition to the normal state, the specific losses are considerably lower than in an analogous sample at constant temperature. A comparison between theory and experiment is presented.         The critical state stability    R. Mints and A. Rakhmanov Summary: A review of the theory of flux jump nucleation in hard and composite superconductors is presented. Stability criteria for some special cases are established. The basic physical ideas and quantitative methods of stability investigation are outlined.         Voltage locking in two coupled microbridge Josephson junctions    D. Jillie, J. Lukens and Y. Kao Summary: Voltage locking, defined as the production of an identical non-zero DC voltage in the absence of external microwave radiation across each Josephson junction of an array, has been observed in two microbridge Josephson junctions separated by a 2/spl mu/m wide strip of superconductor. Voltage locking occurs when the bridges are biased with the current flowing in opposing directions thru the bridges and out the strip connecting them. The voltage across each bridge can be pulled over 1/spl mu/V until each bridge displays an identical non-zero voltage, with the total voltage across both bridges equal to zero. Full locking, as defined above, is observed in excess of 40/spl mu/V. The voltage and temperature dependence of the locking is described.         Properties of superconducting weak links formed by magnetically weakening a short length of a uniform aluminum film    G. Dolan and J. Lukens Summary: The Josephson effect has been studied in uniform aluminum films in which a section about a coherence length long has been weakened by the application of a perpendicular magnetic field. These films, which are about 100 /spl mu/m long, have a constant thickness and width (about 0.04 /spl mu/m X 10 /spl mu/m). The applied field is confined to a strip across the film about 0.5 /spl mu/m in length by lead shield films which are deposited on top of the Al film but are electrically insulated from it. The pronounced Josephson-like features which we observe generally appear for applied fields in the shield gap approximately equal to or greater than H/sub c2/for a similar uhshielded Al film. They persist to applied fields several times H/sub c2/. While we do not observe the Josephson effect for fields much below H/sub c2/this may be a result of heating associated with the higher critical currents at low fields rather than an intrinsic property of the film. We note that heating generally prevents the observation of any Josephson effect in planar Al film microbridges. The magnetically weakened junctions have the unusual property that their resistance R, which is measured at small current in the high field limit, is a strong function of temperature. R diverges near T/sub c/approaching the normal state resistance of the entire strip a few millidegrees below the onset of the zero field resistive transition.         Direct-coupled Josephson full adder    J. Magerlein and L. Dunkleberger Summary: We describe a one-bit full adder circuit constructed from direct-coupled Josephson logic elements. The basic gate, which can perform various logic functions, consists of two Josephson junctions and two resistors connected in a loop. Switching the junctions into the finite-voltage state diverts the bias current into a parallel output line, which is directly coupled through the junctions of successive logic elements. The adder is constructed with a 100 /spl mu/m basic linewidth and 25 /spl mu/m square tin tunnel junctions. It operates under all input data conditions with an add time of about 1 nS and a power dissipation of 1 /spl mu/W per gate.         Critical currents in Al films with a triangular lattice of 1 /spl mu/m holes    A. Hebard, A. Fiory and S. Somekh Summary: Critical currents have been measured in an Al film perforated with a two-dimensional triangular lattice pattern of holes. A pulsed current technique has been used to determine the interaction between the vortex lattice and the hole lattice as a function of temperature and magnetic field. Enhanced critical currents of the perforated specimen, compared to critical currents of a similar unperforated reference specimen, are a result of the strong pinning forces at the edges of the holes which tend to trap the cores of the vortices in the holes. When the flux density matches the hole density, the coherent operation of the vortex hole coupling forces is observed to withstand a driving force from the applied current which approaches the theoretical maximum current carrying capacity of a superconductor. At low temperatures, fast pulse measurements reveal that the super-normal instability transitions tend to be suppressed by the application of a magnetic field, allowing the determination of the flux flow thresholds at temperatures well below T/sub c/.         Nine gigahertz impedance measurements on Ta and Nb point constants    D. Claridge, R. Giffard, P. Michelson and W. Fairbank Summary: The 9 GHz complex impedance of a number of niobium and tantalum superconducting point contacts has been measured as a function of dc bias current. In order to obtain more information, the I-V curve of each junction was also recorded. The impedance measurements are in qualitative agreement with predictions based on the resistively shunted junction model modified to include noise.         Josephson logic circuit with a sinusoidal current supply    K. Lofstrom and T. Van Duzer Summary: We propose here a method of powering latching-type Josephson junction logic circuits by a high-frequency sinusoidal source, allowing parallel connection and automatic resetting during each zero crossing of the supply. Analytical guidelines useful in the design of such circuits are developed.         Toroidal field coil system of the oak ridge EPR reference design    J. Lue and J. Luton Summary: A refined design of the toroidal field (TF) coil system for the Oak Ridge Tokamak Experimental Power reactor (EPR) study is presented. This design is based on cable conductor cooled by force-flow supercritical helium. It uses superconducting multifilamentary Nb/sub 3/Sn for a maximum design field of 11 T at the coil windings. A hybrid system which uses NbTi at low field regions is recommended. The coil structure consists of stainless steel segments welded together to form a continuous stiff honeycomb. Conductor optimization and stability analysis specifically applicable to the forced-flow cooled conductors are given.         A 10-tesla pure tension superconducting toroidal field coil system design    S. Wang, L. Turner, F. Mills, D. DeMichele, P. Smelser and S. Kim Summary: The conceptual design of a 10-Tesla pure tension superconducting toroidal field coil (TFC) system has been developed in sufficient detail to define a realistic design for the TFC that could be built based upon the current state of technology with minimum technological extrapolations.         Designing superconducting toroidal field windings for a fusion-driven actinide burner    J. Murphy, H. Howland and J. Chi Summary: The fusion-driven actinide burner is a tokamak fusion reactor which is designed to dispose of actinide wastes from fission reactors. If a fusion reactor is to operate economically, then the major magnet systems must be designed to be superconducting. The toroidal field coils utilized in the magnetic confinement of the plasma are expected to generate peak fields of approximately 9.2 Tesla. This high peak field necessitates that Nb/sub 3/Sn conductors be utilized. The toroidal field coil is designed to have minimal bending stresses. Although the toroidal field windings carry primarily dc currents, the plasma charging/discharging system imposes ac fields on the windings which vary in magnitude and direction. The superconductor configurations to be utilized have been optimized to achieve low ac losses for the anticipated environment.         Superconducting toroidal field magnet for an experimental tokamak    J. Parain Summary: We have studied a TOKAMAK equipped with superconducting toroidal field coils, to be used for plasma physics experiments. The torus is characterized by a radius of 1.7 m, a magnetic field of 3T and a small aspect ratio R/a = 2.6. These parameters require a conductor with a high current density. The fast rise time of the plasma current, 0.15 s, causes serious losses in the toroidal field coils, introducing additional problems. We describe in the following the main conductor, the mechanical structure, the refrigeration system and the protection scheme.         A preliminary study of the superconducting toroidal magnet for fintor 1 reactor    G. Pasotti, M. Ricci, N. Sacchetti and M. Spadoni Summary: Within the framework of a conceptual design for the fusion reactor FINTOR a superconducting toroidal magnet system has been studied. A D-shaped 24 coil system has been designed. The magnetic field and ripple have been calculated. Several cooling systems have been considered and the circulation of the two-phase helium seems to be the most reliable. Eddy current and hysteresis losses have been calculated for the particular geometry of the composite conductor in the hypothesis of a linear rise of the field. Some aspects of the mechanical structure are also considered.         Conceptual design for an air-core superconducting polodial coil system for the experimental power reactor    S. Wang, L. Turner, P. Smelser and S. Kim Summary: As an integral effort in the Argonne Tokomak Experimental Power Reactor Conceptual Design, design studies on the superconducting ohmic heating (OH) coils and the superconducting equilibrium field (EF) coils were completed. These conceptual designs are developed in sufficient detail with clear information on high current ac conductor design, cooling, venting provision, coil structural support, and zero loss poloidal coil cryostat design. Also investigated is the EF field penetration into the blanket and shield.         Superconducting induction coil for a doublet tokamak experimental fusion power reactor    W. Chen, W. Toffolo and J. Purcell Summary: A superconducting induction coil system was designed for a noncircular tokamak experimental fusion power reactor based on the Doublet concept. This coil system is used for inducing and sustaining the plasma current during the thermonuclear burn. The coil must be cycled in about 2 seconds; thus, it is important to design it for low AC loss during pulsing operation. A braided superconducting cable capable of carrying 450 kA at a central field of 5.65 Tesla was chosen as the conductor. The coil system consists of a central solenoid and 12 outer coils, with a total of 157 series connected turns. The central solenoid has a single layer winding of 134 turns on a fiberglass epoxy spool. The outer coils are located so that the error field generated at the plasma location is limited to a few gauss. The winding is reinforced by prestressed stainless steel bands on the outer surface, so that there is no relative motion between the cable and the coil spool or insulation during pulsing.         Safety systems and structural aspects of superconducting magnets for fusion power reactors    J. Powell, J. Lehner, G. Danby, D. Hsieh, M. Reich and A. Prodell Summary: Potential safety systems are examined for superconducting magnets in fusion power reactors. Because of current and voltage limitations, energy removal systems do not appear practical for dumping significant amounts of energy external to the magnet for designs currently envisioned. Some type of Temperature Equalization System appears necessary to minimize temperature inhomogeneities if energy is dumped internally during a quench or other accident situation since inhomogeneities may cause electrical breakdown and/or structural damage. Large detection nets appear necessary to detect potential "hot spots" before they can damage the magnet. Qualitative fault/event trees have been developed for some potential accident pathways; however, many years will be required before quantitative risk assessment studies can be made.         Superconducting magnet system U-25 MHD facility    R. Niemann, S. Wang, W. Pelczarski, J. Gonczy, K. Mataya, H. Ludwig, D. Hillis, H. Phillips, L. Turner, J. Purcell, D. Montgomery, J. Williams, A. Hatch, P. Marston, P. Smelser, V. Zenkevitch, L. Kirjenen and W. Young Summary: The Argonne National Laboratory has designed and is constructing a superconducting dipole magnet system for use in the bypass loop of the U-25 MHD facility in Moscow. Presented in detail are the system design parameters. Reviewed are the magnet geometry, stability criteria, cryostat thermal and mechanical design, cryogenic system parameters, and controls. Details of the servo mechanism winding machine, the epoxy fiberglass tension member support system, and the diagnostic instrumentation system for monitoring of the magnet's thermal parameters, structural forces and component accelerations during system cool-down and with the Magnetohydrodynamics (MHD) channel in operation are included.         Superconducting magnets for an MHD test facility and base load power plant    Z. Stekly, R. Thome and W. Punchard Summary: The development of Magnetohydrodynamic (MHD) power generation in the U.S. may involve the construction of an Engineering Test Facility (ETF) as a step toward a base load or full-scale power plant. This paper describes the superconducting magnet requirements for the ETF and base load plants and gives the results to date in a program involving production of magnet reference designs for the two systems. Each magnet produces a tapered field profile with a maximum of 6.0 T on axis. Warm bore inlet and outlet diameters for the ETF magnet are 0.9 m and 1.75 m, respectively; and the active field length is 7.0 m. For the full-scale system, the corresponding dimensions are 2.25 m, 4.75 m, and 16 m. Overall electrical and mechanical characteristics for these design points are given. Some of the areas which present unique design and construction problems for magnets of this size are discussed.         Superconductivity defects and stoichiometry in A15 materials    R. Dynes, J. Poate, L. Testardi, A. Storm and R. Hammond Summary: We have fabricated thin films of Nb/sub 3/Ge, Nb/sub 3/Sn, V/sub 3/Si and V/sub 3/Ge and investigated their superconducting and structural properties. In the case of the Nb compounds the dependence of T/sub c/, resistance ratio and phase on stoichiometry have been determined. Defects have also been introduced into these films, in a controlled fashion, by irradiation with 1.9 MeV/sup 4/He particles, and the structural and superconducting properties measured. The results indicate a universality of behavior in these materials and suggest that stoichiometry is not the most crucial parameter in affecting T/sub c/.         Tunneling, X-ray and electron diffraction studies of the structure of Nb/sub 3/Ge films    J. Rowell, P. Schmidt, E. Spencer, P. Dernier and D. Joy Summary: In an attempt to understand the structure of high T/sub c/Nb/sub 3/Ge films we have utilized tunneling, x-ray diffraction and transmission electron diffraction. Tunneling experiments indicate that such films have an appreciable highly disordered component. In x-ray diffraction, only two anomalous diffraction peaks are observed which are not sufficient to identify the unknown phase. The complex electron diffraction patterns are interpreted most easily as evidence for superlattice formation. Finally we show that large lattice expansions and depressions of T/sub c/are produced when Nb/sub 3/Ge films are exposed to hydrofluoric acid, presumably due to inclusion of hydrogen.         Critical current measurements of CVD prepared Nb/sub 3/Ge containing various amounts of second phase (Nb/sub 5/Ge/sub 3/) material    R. Carlson, R. Bartlett, L. Newkirk and F. Valencia Summary: Data are presented which show a relationship between the critical current density and second phase (tetragonal Nb/sub 2/Ge/sub 3/) material in CVD deposited Nb/sub 3/Ge for deposition temperatures ranging from 750 to 900/spl deg/C. The data were measured in the temperature range from T/sub c/(/spl ap/ 21 K) down to 13.8 K and at 4 K for several of the samples. Also reported is the slope of the critical current density with respect to temperature, dJ/sub c//dT. Samples with the largest J/sub c/at 13.8 K also had the largest (dJ/sub c//dT) and the lowest extrapolated intercept of the J/sub c/curve with the temperature axis. J/sub c/at 13.8 K as a function of second phase has a maximum of 2.5x10/sup 6/A/cm/sup 2/for approximately 2 to 3% Nb/sub 2/Ge/sub 3/present in the coat. The temperature dependence of the critical current was represented by J/sub c/(T) = J/sub c/(0)[1-(T/T/sub c/)/sup 2/] for most samples.         Effect of third element additions on the properties of bronze processed Nb/sub 3/Sn    D. Dew-Hughes Summary: The effect of additions of Al, Sn or Zr to the Nb core, together with additions of Al, Ga or In to the bronze matrix, on the rate of layer growths and critical current density of Nb/sub 3/Sn formed by the bronze process has been studied. Small amounts of Al (1.25 wt%) in the core, separately or together with a few percent of Al in the matrix, replacing some of the Sn, increase the rate of growth of the Nb/sub 3/Sn layer. Larger quantities of Al (>2 wt%), of Ga or of In in the matrix decrease the rate of layer growth by more than can be accounted for by the concomitant reduction in Sn content. Low field critical current density is more dependent upon layer thickness and growth rate than upon composition. High field critical current density is directly related to the upper critical field.         Influence of low temperature neutron irradiation on the superconducting properties of V/sub 3/Ga multifilamentary wires    M. Couach, J. Doulat and E. Bonjour Summary: The influence of low temperature neutron irradiation on multifilamentary wires of V/sub 3/Ga has been investigated. The critical field H/sub c2/was measured as a function of temperature in the range of fields 0 to 8 Teslas before, after irradiation and after annealing at room temperature ; so was the critical current I/sub c/(H,T) on the temperature range 4.2 K to T/sub c/. The low field part of the curve H/sub c2/(T) measured in all cases allowed the determination of the Maki parameter and an extrapolation of this curve was done using the Werthamer formula. A decrease of critical current was found, amounting to about 30 % at 4.2 K for the largest irradition dose, 3x10/sup 18/n/cm/sup 2/. The samples were sensitive to room temperature annealing. A plot of the pinning force versus reduced field shows that the samples do not obey a scaling law, except near T/sub c/.         J/sub c/changes after neutron irradiation of Nb/sub 3/Sn at 8 K    B. Brown, T. Blewitt, T. Scott and D. Wozniak Summary: In order to understand radiation effects in fusion magnet materials under operating conditions, the critical current (J/sub c/) and critical temperature (T/sub c/) have been measured up to 3.2 T as a function of dose after fast neutron irradiation at 6 K in Nb/sub 3/Sn/sup 1/and after thermal neutron irradiation at 8 K in 0.1 a/o/sup 235/U-Nb/sub 3/Sn. Experimentally determining an equivalent fast-neutron dose for the latter fission-fragment damage allows comparison of the irradiations. Increases in high J/sub c/material (1.5x10/sup 6/A/cm/sup 2/at 4.5 K and 3.2 T) where observed after 1x10/sup 18/n/cm/sup 2/(E > 0.1 MeV). An extension of the dose up to 2.5x10/sup 19/n/cm/sup 2/resulted in decreases in J/sub c/by a factor of 20 and decreases in T/sub c/from 18 to 11 K. The results are explained by a model that considers enhanced flux pinning (F/sub p/) by the radiation-induced defect cascades at low doses. At higher doses the decreases in T/sub c/dominate and lower F/sub p/. The field dependence of the F/sub p/changes can be explained by considering changes in H/sub c2/The model predicted the observed J/sub c/changes in the/sup 235/U-Nb/sub 3/Sn. The J/sub c/changes differ from those found after neutron irradiations at /spl sim/400 K due to the different flux pinning characteristics of the different defect structures.         The influence of implanted ions on the superconducting transition temperature of transition metals and transition metal carbides    J. Geerk, K. Langguth, G. Linker and O. Meyer Summary: The implantation of several different ions into transition metals and transition metal carbides leads to a strong variation of T/sub c/. In molybdenum layers, T/sub c/was found to increase after implantation of B, C, N, P, As and S ions up to a maximum value of 9.4 K at concentrations of about 25 at. %. No T/sub c/increase has been observed for Ne, Xe and Al implants. Structure determination, resistivity measurements and additional channeling measurements on implanted Mo single crystals indicate that the T/sub c/-enhancement is due to a strongly distorted host lattice. Systematic studies have also been performed for other transition metals. Single crystals of NbC/sub 0.89/and VC/sub 0.88/have been implanted with carbon ions at different temperatures. For NbC T/sub c/increased from 3 to 7 K after implantation at RT and reached a maximum of 11.5 K after annealing at 1100/spl deg/C. VC was found to become superconducting at about 3.2 K after implantation of carbon ions into the single crystal at 700/spl deg/C. Backscattering measurements showed an improvement in the stoichiometry of the implanted regions; channeling spectra revealed that radiation damage was not completely annealed in the hot VC implants.         Measurements of magnet quench levels induced by proton beam spray    H. Edwards, C. Rode and J. McCarthy Summary: A superconducting dipole magnet was installed in the Fermilab primary beam line. Targets were inserted in the proton beam upstream of the magnet and measurements made of the energy deposition within the magnet sufficient to cause quenching. The quench levels were 25 mW/g for 1 sec beam spill and 1 mJ/g for a spill of 1 msec or less. In comparison, the energy deposition at the extraction septum was 0.6 mJ/g.         Stability-optimized, force-cooled, multifilamentary superconductors    L. Dresner Summary: A numerical program has been written to calculate the temperature-time history of a uniformly pulse-heated composite superconductor cooled by supercritical helium in forced convection. The program determines the maximum sudden temperature rise from which the conductor can still recover the superconducting state. The program includes the effects of (1) current sharing, (2) the temperature variation of the specific heat of both the matrix and the superconductor, and (3) the temperature variation of the heat transfer coefficient. Using this program, one may optimize force-cooled conductors with respect to stability by simultaneously varying the copper-to-superconductor (Cu/SC) ratio and the metal-to-helium ratio. Use of stability-optimized conductors allows a given stability level to be maintained for a particular field and bath temperature and the pressure drop and pumping losses to be reduced.         Experimental investigation of training and degradation in superconducting magnet systems(SMS)    O. Anashkin, V. Varlakhin, V. Keilin, A. Krivikh and V. Lyikov Summary: Training and degradation phenomena inherent in SMS, especially in those with complex configuration, are a serious obstacle to the creation of partially stabilized SMS with predictable parameters. The mechanical origin of these phenomena is well recognized, although their more detailed mechanism has not been definitely found. Some of us succeeded in reproducing training and degradation in short samples of superconducting wires strained and charged with transport current in an external magnetic field. No dependence on current charging rate was found-evidence in favor of impulse nature of heat disturbances. Subsequently it was observed that the number of training quenches increases when the heat transfer from the sample decreases ( in these experiments the deterioration of heat transfer was made by placing samples in vacuum instead of liquid helium). All these facts as well as some others argue in favor of serration yielding as the most probable cause of training and degradation. We have carried out a number of experiments studying these phenomena in model circular and oval windings placed in an external superconducting field. The tested windings were separated from the external coil by a separate cryostat. The size of the windings was up to 190 mm, the external field up to 7 T. Potted as well as free-wound samples were tested. They were made of multifilament niobium-titanium wires of different diameter with copper-to-superconductor ratio about 1:1 and 2:1. It was found that the oval windings had much more severe training and degradation than the circular. Some dependences of these phenomena on wire diameter and features of the windings are also reported.         Cryostability of a small superconducting coil wound with cabled hallow conductor    Y. Iwasa, M. Hoenig and D. Montgomery Summary: A commercially fabricated Nb-Ti composite cabled hollow conductor was investigated for its stability in the form of a small (110-mm diameter) coil. The experiment has confirmed the general validity of our earlier theoretical analyses and revealed some unexpected transient effects.         Cryostatic stability equation    S. Sydoriak Summary: As regards recovery from a quench, boiling in narrow channels is shown to be qualitatively superior to pool boiling because the recovery heat flux equals the breakaway flux for narrow channels whereas the two are markedly different in pool boiling. A second advantage of channel boiling is that it is well understood and calculable whereas pool peak nucleate boiling heat flux has been adequately measured only for boiling from the top of an immersed heated body. Peak boiling from the bottom is much less and (probably) depends strongly on the extent of the bottom surface. Equations are presented by which one can calculate the critical boiling heat flux for parallel wall vertical channels subject to either natural convection or forced flow boiling, with one or both walls heated. The one-heated-wall forced flow equation is discussed with regard to design of a spiral wound solenoid (pancake magnet) having a slippery insulating tape between the windings.         Method for estimating the refrigeration costs of supercritical helium cooled cable superconductors    A. Bejan and M. Hoenig Summary: Refrigeration costs constitute an important aspect of the economics of force-cooled cable superconductors. The refrigerator power required to operate a forced cooled superconducting magnet is analyzed. The paper develops a simple method for estimating the total refrigerator power associated with a given length of cabled conductor of specified geometry. The estimate relies on the thermodynamics of supercritical helium in the superconducting cable. Finally, the technique is used to point out what features of the forced cooled superconductor design are desirable from a refrigeration cost standpoint.         Optimization of current leads for superconducting systems    M. Hilal Summary: An optimized current lead in the context of this paper is one cooled by many baffles which intercept heat at fixed refrigerated stages. The helium boil-off-gas from the lead does not cool the leads but is totally utilized via heat exchangers in the refrigeration cycle. Discrete cooling without gaseous heat exchange has the advantage of eliminating the possibility of voltage breakdown in gas near the input leads. A method is presented to optimize a baffle system of fixed temperature shields to intercept heat conducted into a dewar through and generated by the current lead. The refrigeration power required for 1,2,3...n shields is compared with that required for an infinite number of shields, which is the absolute minimum power,P/sub min/, and is given byP_{\min} = 2I\sqrt{T_{H}} \int\min{T_{C}}\max{T_{H}}\sqrt{\frac{\rho k (T_{H}-T)}{T^{3}}}dT, where T/sub c/and T/sub H/are the cold and hot-end temperatures, /spl rho/ is the resistivity, k is the thermal conductivity and I is the transport current. The value P/sub min/I depends on /spl rho/ and k of the material and end point temperatures. Also given is the lead optimization procedure for the case of a load current which is constantly changing with time in some prescribed way. Similar optimization of gas cooled leads with respect to minimizing refrigeration power is given.         Test results of "Tokamak-7" superconducting magnet system (SMS) sections    D. Ivanov, V. Keilin, E. Klimenko, I. Kovalev, S. Novikov, B. Stavissky and N. Chernoplekov Summary: At the Kurchatov Atomic Energy Institute the "Tokamak-7" installation with SMS for the main toroidal field is being built. Design parameters of SMS were published earlier. At this time the testing of parts of SMS is almost complete. Each part represents 1/8 of the magnet system and consists of six double pancakes. The pancakes are wound of multi-channel electroplated strip with parallel niobium-titanium wires. All pancakes are connected in parallel hydraulically and in series electrically. The possibility of additional current in each pancake or group of pancakes is also provided. The test rig comprises a helium refrigerator (600 W at 4.5K), a test cryostat, several power supplies and a diagnostic system. Precooling of the sections takes about 24 hours. During this period, the maximum helium inlet pressure is about 1.6 MPa (abs.). At working conditions the inlet pressure is about 0.2-0.3 MPa (gauge), temperature is in the range 4.5-5.0K, helium flow is about 300 nm/sup 3//h. The highest current was equal to 5650A (maximum design current is 6000A), corresponding to a field at the superconductor of about 3.5T. In some cases the central pancakes were excited with up to 900A additional current. As a rule, the superconducting-to-normal transition occurred in the most peripheral pancakes instead of the most magnetically loaded central pancakes and was caused by shielding currents. The latter have maximum value in the peripheral pancakes. The number and intensity of voltage jumps in the normal zone detection circuit have been much lower than in the test of the CMS-0.25 installation.         Forced flow cooling of ISABELLE dipole magnets    J. Bamberger, J. Aggus, D. Brown, D. Kassner, J. Sondericker and T. Strobridge Summary: The superconducting magnets for ISABELLE will use a forced flow supercritical helium cooling system. In order to evaluate this cooling scheme two individual dipole magnets were first tested in conventional dewars using pool boiling helium. These magnets were then modified for forced flow cooling and retested with the identical magnet coils. The first evaluation test used a 1 m long ISA model dipole magnet whose pool boiling performance had been established. The same magnet was then retested with forced flow cooling, energizing it at various operating temperatures until quench occurred. The magnet's performance with forced flow cooling was consistent with data from the previous pool boiling tests. The next step in the program was a full-scale ISABELLE dipole ring magnet, 4.25 m long, whose performance was first evaluated with pool boiling. For the forced flow test the magnet was shrunk-fit into an unsplit laminated core encased in a stainless steel cylinder. The high pressure gas is cooled below 4 K by a helium bath which is pumped below atmospheric pressure with an ejector nozzle. The performance of the full-scale dipole magnet in the new configuration with forced flow cooling, showed a 10% increase in the attainable maximum current as compared to the pool boiling data.         The MX magnet system    R. Bulmer, M. Calderon, D. Cornish, T. Kozman and S. Sackett Summary: The Lawrence Livermore Laboratory has put forward proposals for building a large mirror fusion experiment called MX (Mirror Experiment). This machine is designed to advance both the physics of mirror systems and the technologies which will be required on future machines such as FERF (Fusion Engineering Research Facility) and reactors. One such technology to benefit is superconductivity, since the confining field will be generated by two large NbTi Yin-Yang shaped coils. The maximum field at the conductor is 7.5 T and the total stored energy is 500 MJ. The paper gives details of the magnet system conceptual design including the design philosophy of the superconductor and the structure to restrain the very large electromagnetic forces.         High energy physics and applied superconductivity    P. Reardon Summary: The purpose of my talk today is to report on the application of superconductivity in the field of high energy physics and I hope to demonstrate to you and even a wider audience that the application of superconductivity in high energy physics is accepted as a proper and proven technology for the conduct of its business. This acceptance required pioneering efforts on the part of many dedicated scientists and engineers. They turned their interests from more parochial pursuits to cope with unfamiliar phenomena, applying their initiative and experimental competence to a new subject with poorly defined boundaries.         Superconducting microbridges in delft    G. Daalmans, T. Klapwijk and J. Mooij Summary: Research in our group is concentrated on superconducting microbridges. Basic properties of bridges as well as the possible application as detectors of (sub) millimeter radiation are investigated. Specific projects discussed in this paper are: a) Ginzburg-Landau calculations on two- and three-dimensional constrictions, I/sub c/(T), I/sub s/(/spl phi/), /spl psi/(x). b) experimental investigations of basic properties of microbridges such as critical currents for various geometries and materials, regimes at finite voltages, thermal properties. c) mutual influence of microbridges close together on the same metal film. d) fabrication of variable thickness niobium bridges suitable for submillimeter detection. e) antenna design for optimum coupling of radiation field into weak link.         Properties of superconducting weak links prepared by ion implantation and by electron beam lithography    E. Harris and R. Laibowitz Summary: In this paper, we present our latest results on the properties of superconducting weak links prepared in Mo films by ion-implantation and in Nb films by electron-beam lithography. In the case of the ion-implanted weak links, which structurally resemble proximity-effect bridges, we find that the static properties are quite well described by a recent theory of Likharev and Yakobson. We further find that the rf response of these weak links is in excellent agreement with quasistatic resistively-shunted-junction model calculations based on a sinusoidal current-phase relation at those temperatures for which such a current-phase relation is predicted by the static theory of Likharev and Yakob-son. For the e-beam fabricated Nb bridges, which have the Dayem bridge geometry, our sample preparation techniques have allowed us to produce bridges and two-junction interferometers in which the link dimensions are as small as about 2000 Angstroms. We find that Josephson effects are observable in these bridges even when the bridge dimensions exceed the temperature-dependent coherence length by about an order of magnitude, but are still less than the effective thin-film penetration depth.         Comparative studies of ion-implant Josephson-effect structures    R. Kirschman, J. Hutchby, J. Burgess, R. McNamara and H. Notarys Summary: We have investigated Josephson-effect structures formed by Cu or Fe implant of localized regions in Ta films and have compared their properties to those of other types of proximity-effect bridges. Properties investigated include coherence length, penetration depth, critical current versus temperature, critical current versus magnetic field, and rf response. We find no significant differences between the various types of bridges, provided a material-dependent scaling factor is applied to the bridge length.         Properties of new types of niobium weak links    B. Boone, C. Arrington, Li-Kong Wang and B. Deaver Summary: Measurements have been made of the characteristics of weak links fabricated in several different ways from thin films of niobium. Weak links have been made in films of uniform thickness by implanting ions into a narrow line across a long thin Nb strip and in variable thickness (thick-thin-thick) form by depositing thick films of Nb, Sn, In or Pb on top of a thin Nb strip, leaving a short thin bridge joining two large thick pads. Bridges about 1 /spl mu/m long and 1-30 /spl mu/m wide have been studied by measuring the I-V curves as a function of temperature, applied microwave power and magnetic field. These weak links exhibit Josephson effects, have characteristics that can be interpreted as multiple flux flow, and have other features that can be explained phenomenologically in terms of a relaxation time of the order parameter.         Improved performance of tin variable-thickness superconducting microbridges    M. Octavio, W. Skocpol and M. Tinkham Summary: We have fabricated tin variable-thickness microbridges with which we have observed the ac Josephson effect to as high as 3.7 mV, corresponding to the 187th harmonic of X-band radiation. The dc I-V curves of the bridges show reduced hysteresis and strong subharmonic gap structure to very low temperatures. We use the gap structure as a local thermometer in order to demonstrate that the improved high-frequency performance correlates with the more efficient removal of Joule heat from these bridges.         Controllable superconducting weak links    T. Wong, J. Yeh and D. Langenberg Summary: We report the experimental characteristics of controllable superconducting weak links (CLINKs), in which the necessary localized weak region is produced by creating a nonequilibrium excess quasiparticle population which suppresses the superconducting order parameter. Direct quasiparticle injection, photo-injection, and phonon injection have been used. The characteristics (e.g., critical current) of these CLINKs can be electrically or optically tuned continuously at any temperature below T/sub c/. The ac Josephson effect has been observed in each type. We have developed a rudimentary theory which appears to account for some of the experimental observations. The theory is based on the phenomenological Rothwarf-Taylor equations for a nonequilibrium superconductor, modified to include quasiparticle and phonon diffusion spatial dependence of the densities, together with the modified heating or T* model of Parker and existing theoretical models of weak links.         Energy spectra of phonons emitted from a nonequilibrium superconducting thin film    Jhy-Jiun Chang and D. Scalapino Summary: Results of a theoretical investigation of the energy spectra of phonons generated by a superconducting thin film under IR and optical pumping, phonon injection via heat pumping, and electron injections through SIS tunnel junctions are reported. The coupled quasiparticle and phonon kinetic equations and a modified BCS gap equation are used as the basis of our study. The use of the thin films as phonon generators or phonon convertors to produce narrow band phonons of energy in the meV range and the mechanisms that limit the bandwidth are discussed.         Results from the MIT-EPRI 3-MVA superconducting alternator    J. Smith, G. Wilson, J. Kirtley and T. Keim Summary: A summary report is given of the experience gained in the design, construction and testing of a 3-MVA synchronous machine with a rotating superconducting field winding. Included are the objectives and chronology of the project, a brief description of the machine, and a summary of test results. Conclusions are presented and key problem areas requiring additional work are outlined. Plans to build an advanced concept machine are given.         High speed superconducting generator    R. Blaugher, J. Parker and J. McCabria Summary: The Westinghouse Electric Corporation under USAF sponsorship is currently involved in a technology development program directed toward the design, construction, and test of a 12,000 rpm, ac generator, with a design capability of 10 MVA, utilizing a superconducting field winding. The first phase of this program, which was completed in early 1974, demonstrated that a four-pole superconducting rotor could be spun at 12,000 rpm with the field excited to the design current level. This program is currently in its second phase with the construction of a complete generator. The design of the second-phase rotor is generally based on the information obtained from the phase-one effort and involves design changes in the superconducting coils, insulation system, helium flow scheme, and mechanical approach. It is intended that full-power tests on the complete generator be conducted in 1977. This paper will review the generator design with special emphasis on the cryogenic and mechanical features. Design changes relative to the phase-on rotor will be discussed, followed by a review of the test objectives. Finally certain features of future machine designs and requirements will be discussed.         A two-phase cooling system for superconducting A-C generator rotors    T. Laskaris Summary: An analytical study of a two-phase cooling system for rotors of superconducting A-C generators is presented. The system employs a two-phase, irreversible flow process to deliver the helium to the superconducting winding such that the liquid is separated from the vapor by the rotation and forms a pool. The free surface of the pool is maintained at subatmospheric pressure and the winding, which is partially immersed in the liquid, is cooled by pool boiling at temperatures below 4.2 K. The essential feature of the process is the ability to externally control the level of liquid in the rotor, and to regulate the mass flow rate through the rotor to meet its steady state and transient requirements, irrespective of the rotational speed.         Thermal performance of the rotor of the MIT-EPRI 3 MVA superconducting alternator    A. Bejan and P. Thullen Summary: The MIT-EPRI 3 MVA superconducting alternator has undergone a number of successful electrical and mechanical tests. During these tests a great deal of information on the thermal performance of the rotor has been collected. This information has not been presented in the literature or discussed generally. Thermal performance data of interest to generator designers such as: helium flow circuit behavior and conceptual design, electrical lead performance following reconstruction and shield thermal performance is discussed.         Superconducting D.C. machines: A 1 MW propulsion system; studies for commercial ship propulsion    A. Appleton, T. Bartram, R. Potts and R. Watts Summary: This paper describes the commissioning and some of the tests which have been carried out on a superconducting propulsion system comprising a 1 MW superconducting generator and a 1340 hp superconducting motor. The design, construction and tests on the system have taken place over a period of 5 years and the paper presents some construction and operational experience. The major problems were the behaviour of the helium compressor and a 'cold leak' on the generator cryostat. The paper also presents the results of studies which have been carried out in the use of superconducting propulsion systems in a number of types of ship. The studies were carried out by IRD in close liaison with the British Ship Research Association and a large British Shipbuilder.         Superconducting A.C. generators: Progress on the design of a 1300 MW, 3000 rev/min generator    A. Appleton, J. Ross, J. Bumby and A. Mitcham Summary: This paper describes the design of a 1300 MW superconducting a.c. generator. Considerable attention has been given to the properties of the low temperature rotor forging, the rotor screen and the construction of the stator support structure. A forging has been purchased for metallurgical examination but the results will not be available in time for the conference. The effects of changing the material of the rotor screen are described.         A superconductive field winding subsystem for a 3000 hp homopolar motor    R. Ackermann, R. Rhodenizer and C. Ward Summary: A superconductive field winding subsystem has been developed for a 3000 hp homopolar motor for a model ship propulsion system. This subsystem includes a large NbTi superconductive coil mounted in a cryostat designed to withstand relatively severe environmental conditions expected during the ship-board tests planned by the Navy. Other components are a 2.5 kVA exciter for energizing the windings, an instrumentation console for monitoring system operation and a transfer line to permit operation with batch quantities of liquid helium. An overall description of the design and construction of the individual components in the system is presented along with a summary of preliminary component test results.         Superconducting linear synchronous motor tests    D. Atherton, A. Eastham, J. Cunningham, S. Dewan, G. Slemon and R. Turton Summary: We have tested a large superconducting linear synchronous motor designed for high-speed magnetically levitated vehicles. A single superconducting magnet, from the array of 45 carried by the proposed vehicle, interacts with guideway windings mounted on the rim of a 7.6 m diameter rotating wheel. The split 3-phase "stator" windings are energized from a variable-frequency 40 kVA current-source inverter power supply. All forces and torques developed on the magnet have been monitored over the complete 360/spl deg/ cycle of force angle for a range of suspension heights, lateral displacements, and pitch, roll and yaw angles, at speeds up to 100 km/h. Controlled starting, stopping and section entry have been demonstrated. The results are in excellent agreement with analysis based on mutual inductance computations and on a coupled circuit model of the machine. Highlights of the results are discussed.         Brushless superconducting alternators    O. Mawardi, S. Muelder and R. Michelotti Summary: A report is presented on the program at CWRU to demonstrate the feasibility of a brushless superconducting alternator. In this machine the rotating field windings of the generator are excited by a flux pump. In this manner the conventional slip rings used to lead the current to the windings are eliminated. Some of the novel features of the generator are the large current in the field windings and the rapid dynamic response to faults.         Evaluation of superconductors for large scale switching of electrical power    K. Gray, W. Chen and R. Huebener Summary: The extreme difference between the electrical resistance of a superconductor in the superconducting and the normal state suggests its application in various large scale switching operations of electrical power. We have performed a theoretical evaluation of such applications in a superconducting rectifier operating at 60 Hz both for magnetic and thermal switching. Operation in both liquid helium and hydrogen has been considered. Based on an optimistic evaluation of the materials parameters expected to become available, neither mode of operation appears feasible. For magnetic switching the difficulty arises mainly from the large magnitude of the switching losses. This requires operation using a relatively low critical field, which is incompatible with the high normal resistivity needed in an efficient switch. Thermal switching at 60 Hz appears infeasible because of the incompatibility of a fast thermal time constant and a reasonably large temperature increment above the temperature of the liquid coolant. These problems are absent in devices operating at frequencies much less than 60 Hz, and various potential applications will be discussed.         Calorimetric studies of composite superconductors based on Nb/sub 3/Sn    H. Gegel, D. Yeh, J. Pajor and J. Ho Summary: Heat capacity measurements between 4 and 24 K have been made on Nb/sub 3/Sn composite superconductors. The results are shown to be useful in determining the degree and uniformity of the compound formation through solid state reactions. Considering its simplicity and sensitivity, low temperature calorimetry should be considered as one of the practical techniques for materials characterization and manufacturing processes evaluation.         Properties of multifilamentary Nb/sub 3/Sn conductors    H. Hillmann, H. Kuckuck, H. Pfister, G. Rupp, E. Springer, M. Wilhelm, K. Wohlleben and G. Ziegler Summary: Measurements on Nb/sub 3/Sn multifilamentary conductors show that normally a degradation of the transition temperature T/sub c/and of the critical current I/sub c/occurs as a result of the compressive strain exerted by the bronze on the Nb/sub 3/Sn layers when cooling down. When tensile stresses are applied, therefore, an increase of the I/sub c/up to a maximum value is observed at first and then the I/sub c/begins to decrease. These compressive strains are favourable factors when the conductor is subjected to tensile and bending loads. A coil reacted after winding produces a flux density of 12 T in a 7.5 T background field. The measured I/sub c/values were 10 % higher than in short samples. A coil wound with pre-reacted conductors produces a flux density of 13 T in an 8 T background field and, with an insert coil in the 55 mm bore of this magnet, 14.5 T has been measured.         Critical current of multifilamentary Nb/sub 3/Sn - insert coil and long sample bend tests    A. Petrovich, B. Zeitlin, J. Cutro, M. Walker and C. Rosner Summary: Cabled and monolithic multifilament Nb/sub 3/Sn conductors have been prepared utilizing various manufacturing approaches. One insert coil and eighteen samples, each approximately two meters in length, have been tested for critical current carrying capability in a background field of 10 T at 4.2 K. The various conductor configurations were evaluated in both the wind-after-react (WAR) and react-after-wind (RAW) conditions. Achievable bend diameters and critical current degradation due to bending are reported as a function of the level of sensitivity for detection of the onset of resistive behavior. Levels of critical current density as high as 10/sup 5/Amperes/cm/sup 2/(bronze and filament area) were observed. Bend diameters as small as 1.9 cm appear to be achieved in conductors carrying 100 to 300 amperes, depending upon the level of resistivity which can be tolerated for the conductor application. The 4.5 cm I.D. potted react-after-wind coil performed to short sample critical current producing 1 T in the 10 T background field.         The influence of thermally induced matrix stresses on the superconducting properties of Nb/sub 3/Sn wire conductors    T. Luhman and M. Suenaga Summary: The superconducting critical temperature, T/sub c/, critical current density, J/sub c/, and upper critical field H/sub c2/have been measured on bronze-processed Nb/sub 3/Sn monofilament conductors prior to and after etching away the bronze matrix. Each superconducting parameter showed significant changes when the bronze matrix was removed. It is shown that the source of these changes are stress induced by thermal contraction of the bronze matrix.         The effect of ternary additions to Nb/sub 3/Sn on the upper critical field at 4.2K    R. Akihama, K. Yasukochi and T. Ogasawara Summary: The effect of ternary additions of Group III/sub b/-IV/sub b/metallic elements (Al,Ga,In, Tl,Pb) to Nb/sub 2/Sn on the upper critical field H/sub c2/(4.2K) has been studied. Samples were prepared by arc melting in an argon atmosphere. The measurements of H/sub c2/(4.2K) were performed with a pulsed magnet, and the value of H/sub c2/was determined from measurements of the electrical resistivity. H/sub c2/(4.2K) of the Nb/sub 3/Sn compounds was observed to increase by about 70 KG to a maximum of 300 KG through the replacement of several percent of the Sn by Group III/sub b/-IV/sub b/metallic elements. Of these systems, Nb/sub 3/(Sn-In) and Nb/sub 3/(Sn-Pb) were also prepared by the diffusion method: Cold-rolled tapes of Nb doped with the third element were immersed and heat treated in a Sn bath or a Cu-30wt%Sn bath. H/sub c2/as high as 270 KG was achieved for the Nb/sub 3/(Sn-In) tape prepared in the Cu-30wt% Sn bath at a reaction temperature of 850/spl deg/C. The critical current of this tape was substantially higher than that of the standard Nb/sub 3/Sn tape in a high field region.         High current superconductors for tokamak toroidal field coils    W. Fietz Summary: Conductors rated at 10,000 A for 8 T and 4.2 K are being purchased for the first large coil segment tests at ORNL. Requirements for these conductors, in addition to the high current rating, are low pulse losses, cryostatic stability, and acceptable mechanical properties. The conductors are required to have losses less than 0.4 W/m under pulsed fields of 0.5 T with a rise time of 1 sec in an ambient 8-T field. Methods of calculating these losses and techniques for verifying the performance by direct measurement are discussed. Conductors stabilized by two different cooling methods, pool boiling and forced helium flow, have been proposed. Analysis of these conductors is presented and a proposed definition and test of stability is discussed. Mechanical property requirements, tensile and compressive, are defined and test methods are discussed.         H/sub c1/ of niobium stannide: 200 gauss or over 1000 gauss?    R. Shaw, B. Rosenblum and F. Bridges Summary: The microwave surface resistance of a type II superconductor is a very sensitive measure of the density of vortices in the region a few penetration depths from the sample surface. The surface resistance can be quite insensitive to the usual defect pinning and provides an excellent method for studying the often difficult to measure lower critical field H/sub c1/. Various surface barrier effects exhibit themselves quite clearly. We have examined the low field properties of several superconductors including a series of Pb-In alloys. The values of H/sub c1/we deduce from these measurements correlate very well with the values determined by earlier magnetization studies. We find that the low field microwave properties of highly stoichiometric, low flux pinning samples of Nb/sub 3/Sn are qualitatively the same as those of the Pb-In alloys and other materials. The H/sub cl/we determine for Nb/sub 3/Sn is 1400 /spl plusmn/ 100 gauss. This is well above the values for H/sub c1/widely assumed. We believe that previous determinations are in error. The low ac loss and the lack of flux penetration in Nb/sub 3/Sn, which has been interpreted in terms of a low H/sub cl/and a delayed flux entry by surface barriers, is actually largely due to the high H/sub c1/in most cases. The favorable implications for practical applications of this high H/sub c1/for Nb/sub 3/Sn are discussed.         Critical current properties of multifilament V/sub 3/Ga wire at temperatures above 4.2 Kelvin    D. Howe, T. Francavilla and D. Gubser Summary: Studies of the superconducting properties of V/sub 3/Ga formed in composite wires by solid state reaction are presented. Multifilament wires were fabricated containing nineteen V-6.1 at.%Ga filaments or thirty V-8.0 at. %Ga filaments in a Cu-17.5 at .%Ga matrix. A study of J/sub c/as a function of magnetic field and temperature on these wires is reported. At a temperature of 8.6 K, and in a magnetic field of 10 Tesla, a J/sub c/of 4.2x10/sup 5/amps/ cm/sup 2/was measured for the thirty filament wire. This is significantly higher than the J/sub c/of commercially available V/sub 3/Ga tape Or Nb/sub 3/Sn wire, These studies indicate that not only does our V/sub 3/Ga wire exhibit high magnetic field properties Superior to those for commercially available wire at 4.2 K, but it also retains its superior J/sub c/values at temperatures in excess of 11 K.         Metallurgical and physical properties of ternary Molybdenum Sulfides (M/sub x/Mo/sub 3/S/sub 4/) as synthetized in the bulk state    R. Flukiger, H. Devantay, J. Jorda and J. Muller Summary: The compounds M/sub x/Mo/sub 6/X/sub 8/(M=Pb, Sn, Cu, x =S, Se) crystallizing in the rhombohedral Chevrel phase have been prepared by melting under a pressure of 100 bars of argon and temperatures above 1700/spl deg/C . The variation of the superconducting transition temperature as a function of the concentration x was studied in the systems Cu/sub x/Mo/sub 6/S/sub 8/and Cu/sub x/Mo/sub 6/Se/sub 8/. The microscope observation of these compounds leads to the conclusion that the phase forms congruently. Large single crystals have been prepared. The temperature at which the rhombohedral phase transforms to the orthorhombic structure decreases strongly if the Cu content increases.         Pressure composition effects on superconducting A15 compounds    R. Blaugher Summary: The phase stability of "bulk" A15 compounds prepared using ordinary metallurgical technique is contrasted with high pressure-high temperature synthesis in relation to the formation of high T/sub c/"stoichiometric" compounds. Alloys of Nb-Ge, Nb-Al, and Nb-Ga were prepared by standard metallurgical procedures and subsequently submitted to simultaneous high pressure-high temperature treatment. These materials were characterized as to phase development and superconducting properties to evaluate the influence of the high pressure treatment. The results indicate that high T/sub c/materials may ultimately be obtained by high pressure-high temperature synthesis. The high pressure phase stability of A15 compounds is discussed. The phase formation of off-stoichiometric high T/sub c/A15 compounds is also presented in terms of a non-equilibrium process involving a high quench rate.         Test and evaluation of conductors for superconducting magnetic energy storage    R. Schermer and W. Hassenzahl Summary: We have constructed pancake coils of a monolithic conductor and several different types of braid and cable, using a variety of insulating tapes and bonding resins. The coils were tested to quench in self-field at currents up to 2700 amperes. Results are presented for the training behavior of the various coils as compared to short-sample tests. A conductor composed of several braids or cables in parallel, which will be suitable for the in situ fabrication of large magnets is described.         Fluxoid pinning in bulk Niobium by voids produced during neutron irradiation    C. Koch, H. Freyhardt and J. Scarbrough Summary: Fluxoid pinning due to voids has been studied in niobium irradiated at temperatures from 460 to 1080/spl deg/C. T/sub c/decreased slightly and H/sub c2/increased with irradiation temperature indicating possible O/sub 2/contamination. The J/sub c/vs H behavior was more complex, with maximum J/sub c/values obtained in the samples irradiated at 790 and 940/spl deg/C. With the measured superconducting parameters, and data on void size and distribution, our results were quantitatively compared with expressions for void pinning using the statistical theory of Labusch. Of particular interest in this study was the sample irradiated at 790/spl deg/C which has an ordered void super-lattice.         A quench-age method for the fabrication of Nb(Al) superconductors    R. Ciardella, M. Dariel, J.L.-F. Wang and M. Pickus Summary: The possibility of taking advantage of the extended, high temperature solid solubility of Al in Nb in order to produce composite Nb-Nb/sub 3/Al superconductors was investigated. Rapid quenching after an elevated (1950/spl deg/C) solution treatment makes it possible to retain at room temperature a metastable solid solution containing up to 21 at.% Al. The solid solution transforms into the A-15 phase in the course of a short and relatively low temperature(1000/spl deg/C) aging treatment. The inductively measured onset of superconductivity was 17.6 K in a 100 /spl mu/m thick core of Nb/sub 3/Al embedded in a Nb matrix and prepared by the quench-age method.         High specific heat metals for use in superconducting composites    S. Rosenblum, H. Sheinberg and W. Steyert Summary: In an effort to enhance adiabatic stability, copper containing percentage amounts of Gd/sub 2/O/sub 3/powder was prepared. The specific heat (C/sub v/) of the resulting material was measured at temperatures from 2 to 12 K in zero and 2.4 T applied magnetic field. Below 5 K the C/sub y/is one to two orders of magnitude higher than that of ordinary copper. For example, at 3.7 K in zero field the C/sub v/of 2.4% GdAlO/sub 3/is 1.5 mJ/g-K and for 7.2% Gd/sub 2/O/sub 3/C/sub v/is 3.7 mJ/g-K. These results are only weakly dependent on the magnetic field. Resistance ratios (room temperature to 4 K) of 99 to 46 are obtained, depending on the method of preparation. Mechanical properties of the copper seem good; photomicrographs of the material are shown. Additional cost for materials is $1.20 per pound for 3% oxide in copper. In superconducting applications a fault which reduces the magnetic field on the copper will actually lower the temperature through adiabatic demagnetization unless there is an appreciable heat imput. At 4 K, for example, a 3% oxide material could absorb the heat required to raise pure copper to 11 K, with no change in temperature. It is hoped that this "doped" copper will provide more adiabatic stability for composite superconductor-copper wires than pure copper alone.         Preparation and superconducting properties of Lithium Titanate    U. Roy, A.D. Gupta and C. Koch Summary: Several methods to prepare superconducting lithium titanate are described. Material characterization has been performed by optical metallography and powder x-ray diffraction technique. The critical temperature, T/sub c/and critical current density, J/sub c/, (as a function of the applied field H up to 7.0 T) have been measured. In our specimens T/sub c//spl ap/ 11.4 K, H/sub c2/(4.2 K) > 7.0 T and J/sub c/< 10/sup 7/Am/sup -2/. Possible methods to increase J/sub c/in this material are discussed.         On the superconducting properties of the V/sub 2/Hf-base laves phase compound tapes    K. Inoue and K. Tachikawa Summary: V/sub 2/Hf-base Laves phase compound tapes were fabricated by two different processes. The first of them is the composite process in which the Laves phase layers are formed by the diffusion between the vanadium sheath and the Hf/sub 0.4/Zr/sub 0.6/alloy core. Critical current density J/sub c/and upper critical field H/sub c2/of the V/Hf/sub 0.4/Zr/sub 0.6/composite tape rapidly increase with decreasing temperature. At 1.7 K the Laves phase layer in the V/Hf/sub 0.4/Zr/sub 0.6/composite tape shows H/sub c2/of 254 kOe and J/sub c/(150 kOe) of 2x10/sup 5/A/cm/sup 2/which are higher than those reported for the commercially available Nb/sub 3/Sn and V/sub 3/Ga. The second process is the direct plastic deformation process in which the arc-melted V-Hf-Nb alloys, including the Laves phase, were cold-rolled into tapes. The V- 17at%Hf-16.3at%Nb tape shows transition temperature T/sub c/of 9.5 K and the overall critical current density of 1x10/sup 4/A/cm/sup 2/at 100 kOe and 4.2K.         Ultra high-current superconducting cables for a 2.2-tesla, 300-kilojoule energy storage magnet    G. Miranda, R. Rhodenizer, P. Rackov, W. Punchard and T. De Winter Summary: We have built and tested two types of superconducting cables to be used in pulsed energy storage magnets for the LASL Magnetic Energy Transfer and Storage (METS) program. These 2.2-T, 300-kJ magnets are to operate at 10 to 12 kA with a safety factor in critical current of about 50% at 10 kA. The conductor must exhibit low losses in addition to being stable. Magnetic Corporation of America (MCA) designed a flat conductor using 1224 copper-matrix, monofilament wires combined in two stages of cabling followed by two stages of flat braiding. Two of these conductors were constructed, one with wire already on hand and the second using wire made specifically for this application. Intermagnetics General Corporation (IGC) designed two rectangular conductors using 315 and 319 mixed-matrix multifilament wires combined in three stages of cabling followed by compaction in a Turk's head. The maximum transport current capabilities (I/sub T/) of these cables were measured in hairpin shaped samples with the straight section under test in perpendicularly applied fields. The measured results at 2.5 T for the two MCA cables were 11.7 kA and 15.4 kA, and for the IGC cables were 18.2 kA and 19.3 kA (extrapolated). In addition, samples of the compacted and uncompacted major strands from the IGC cables were tested. The results of these measurements are compared with values of I/sub T/calculated from the single-wire critical currents taking into account the adjacent conductor fields and the cable self-fields. Several causes of degradation of I/sub T/in the compacted cable are discussed including those due to experimental factors.         Superconducting performance of production NbTi alloys    D. Colling, T. De Winter, W. McDonald and W. Turner Summary: A producer of multifilamentary NbTi superconducting composites must depend on specified and uniformly reproduced production quantities of NbTi. Characterization of commercial NbTi starting diameter rod has sug-tested that impurity content, nonmetallic inclusion content and mechanical properties of the NbTi may also affect superconducting performance of multifilamentary wire. This paper describes the superconducting performance, i.e. critical current density at field of commercial NbTi containing 45 to 46.5 wt. pct. Ti and analyzes the influence of NbTi mechanical properties on superconducting performance. Production billets with Cu/NbTi ratios of 1.25:1 to 5.5:1 which contain as many as 2046 NbTi filaments are included in this survey. All billets were extruded and drawn to final size with constant major heat treatment and 90-97% reduction after major heat treatment. Superconducting critical current density is shown to be a function of total reduction of NbTi under these conditions, with values of 2.4x10/sup 5/A/cm/sup 2/(4T), 2.0x10/sup 5/A/cm/sup 2/(5T), and 1.6x10/sup 5/A/cm/sup 2/achieved reduction ratios from starting rod size to final filament size of 10/sup 5/or better. Superconducting performance of NbTi heats with tensile reductions in area of 65.5% to 80.5% do not support the suggestion that more ductile NbTi produces higher current density filaments. Mechanical properties appear to be too simple a parameter to predict superconducting performance of NbTi.         Damage to stabilizing materials by 400 GeV protons    P. Sanger, B. Strauss, R. Boom and G. Kulcinski Summary: A study of the radiation induced resistivity resulting from 400 GeV protons was made. The pulsed beam of the Fermi National Accelerator Laboratory was used with an intensity of 6x10/sup 12/protons per pulse at 400 GeV with a slow spill of approximately 1 sec. The instantaneous irradiation rate on the sample is 1.5x10/sup 13/p/cm/sup 2//sec. The resistivity of copper increased linearly with proton fluence at a rate of approximately 3.6x10/sup -25//spl Omega/m/p/cm/sup 2/. Subsequently isochronal annealing was performed. Following the first room temperature anneal, 16% of the induced resistivity was still present. Subsequent irradiations of the same sample indicate that this residual resistivity increases with each irradiation with a tendency to saturate at a higher resistivity. The annealing results and the effects of repeated irradiations will be discussed in detail.         Pulse loss and voltage measurements on superconducting magnets    S. Shen and H. Yeh Summary: This paper describes an electrical method for measuring pulse losses and compensated voltage in superconducting magnets. Test results from two pulsed solenoids are recorded and analyzed digitally by computer. Dependance of loss performance on B/sub max/and B is studied. The effects of conductor motion and presence of normal metal on the loss performance are also discussed.         A computer model for noise in the DC SQUID    C. Tesche and J. Clarke Summary: A computer model for the dc SQUID is described which predicts signal and noise as a function of various SQUID parameters. Differential equations for the voltage across the SQUID including the Johnson noise in the shunted junctions are integrated stepwise in time. Noise-rounded I-V characteristics are computed as a function of applied flux, /spl Phi//sub a/, and ring inductance, L. A measure of the SQUID response, dV/d/spl Phi//sub a/, is calculated as a function of bias current. Low frequency voltage power spectral densitiesS\min{v}\max{o}computed for various /spl Phi//sub a/and L show considerable variation from the corresponding single junction Values. The flux resolution(S\min{v}\max{o})^{1/2}/ (dV/d\Phi_{a})as a function of bias current is computed for several values of L and /spl Phi//sub a/. The results are in good agreement with experiment.         Silicon-barrier Josephson junctions in coplanar and sandwich configurations    M. Schyfter, J. Maah-Sango, N. Raley, R. Ruby, B. Ulrich and T. Van Duzer Summary: Recent considerations on sandwich-type crystalline-silicon-barrier Josephson junctions are given. We show how low-shunt-capacitance electrode configurations can be realized on the thin silicon membranes. As an extension of our work on sandwich-type silicon-barrier devices, we have fabricated junctions with coplanar electrodes separated by a narrow gap on a highly doped silicon surface. These show supercurrents in the range of 1-10 mA for gaps in the range of 0.1-0.3 /spl mu/m in a strip of 30 /spl mu/m width and a surface doping of about 2x10/sup 20/cm/sup -3/. In both structures, small changes can be made to obtain the behavior of a super-Schottky diode rather than a Josephson junction. These diodes are found to have high sensitivities (S=2000 to 2300 V/sup -1/) and can be designed to have low series resistance.         Critical current densities in superconducting granular Al-Al-/sub 2/0-/sub 3/films    D. Abraham, S. Alterovitz and R. Rosenbaum Summary: This paper reports measurements of the critical current densities on thin granular superconducting Al-Al-20-3 films as a function of the normal state resistivity of the granular material and as a function of temperature. It is observed that the Al-Al-20-3 films exhibit critical current densities of 10/sup 2/A/cm/sup 2/to 10/sup 3/A/cm/sup 2/over a broad range of normal state resistivities ranging from 30 /spl mu//spl Omega/cm to 3000 /spl mu//spl Omega/cm; the critical current density is inversely proportional, approximately, to the square root of the normal state resistivity, and in most cases, is directly proportional to (1 - T/T/sub c/). SQUID quantum devices having very large widths of 10 /spl mu/m to 25 /spl mu/m have been prepared from these very low critical current films.         Nonlinear effects in coupled Josephson devices    Y. Imry and P. Marcus Summary: The nonlinear equations for two magnetically coupled Josephson point junctions driven by a current source in the presence of an applied field and including capacitive and dissipative currents have been accurately solved numerically. The asymptotic periodic behavior is used to determine the static current-voltage characteristic, which has three parts connected by constant current steps - a zero-voltage part in which the phase differences of the junctions tend to constant values, an intermediate-voltage part in which current and voltage slowly "beat" between the junctions and a high-voltage part approaching the constant resistance line. The dynamic characteristic for slowly increasing and decreasing currents shows hysteresis and the positions of the voltage jumps are sensitive to the applied field.         Calculation of threshold curves for Josephson quantum interference devices    B. Landman Summary: In many applications of Josephson quantum interference devices, or interferometers, it is important to know the threshold curve which relates the maximum zero-voltage current of the device to the externally applied magnetic field. Generally there is no analytic expression for this curve available and numerical calculation is required. Several such techniques are discussed emphasizing one found to be most rapid in execution. This latter technique treats the problem as that of maximizing the zero-voltage current subject to the constraints that the sum of the phase differences of the superconducting order parameter across junctions and inductances in each interferometer loop be an integral multiple of 2/spl pi/. Lagrange multipliers are used to formulate the constraints and to obtain simultaneous nonlinear equations whose solution yields the threshold curve. These equations are solved using the multi-dimensional Newton-Raphson iteration procedure. An implementation of this technique has been programmed in APL and has calculated 50 point threshold curves in times as small as 2 minutes. Aspects of this implementation are discussed and examples of threshold curves are given.         Thin film Niobium SQUIDs at 20 MHz and 9 GHz    F. Rachford, S. Wolf, J. Hirvonen, J. Kennedy and M. Nisenoff Summary: Niobium thin film SQUIDs containing various types of weak link configurations have been studied at 20 MHz and at 9 GHz. Structures seen in the microwave response of these devices are similar to the hysteretic steps seen in the normal to superconducting transition of soft superconducting microbridges which have been attributed to the generation of phase slip sites in the weak link. The quasiparticle diffusion length for niobium associated with the phase slip sites is nearly temperature independent, and is found to be less than a micrometer in length, approximately an order of magnitude shorter than the corresponding value for tin. The temperature range of operation and the noise characteristics of these devices operated as rf-SQUIDs at 20 MHz appear to vary inversely with the ratio of the quasiparticle diffusion length to the zero temperature coherence length inferred from the microwave data. The minimization of this ratio should result in better SQUID response at all excitation frequencies.         Performance factors in rf SQUIDs--High frequency limit    R. Buhrman and L. Jackel Summary: The mode of operation of rf SQUIDs in the limit where the bias frequency /spl omega/ exceeds the natural R/L frequency of the SQUID ring is analyzed. Optimum coupling conditions are presented and the intrinsic noise limits are discussed.         Perturbation theory of injection locking for Josephson junction oscillator    K. Acharya and E. Thompson Summary: The system consisting of a Josephson element inside a resonant cavity biased by a current source has been analyzed from the circuit point of view. The dynamical equations for an ideal Josephson element shunted by a resistance and an external linear circuit in series with a rf voltage source are solved by a systematic perturbation theory. When the rf voltage is zero, these solutions describe the cavity induced step and for a non zero rf voltage, these solutions indicate the phenomenon of phase locking. The lock range is obtained as a function of the cavity Q, the coupling of the element to the cavity, the critical junction current and the incident power. The results are compared with the Longacre and Shapiro theory of the magnitude of the cavity induced step, the general phase locking theory of Adler and the experimental results of Stancampiano and Shapiro.         Picosecond pulses from Josephson junctions: Phenomenological and microscopic analyses    R. Peterson and D. McDonald Summary: A Josephson junction modeled by the phenomenological current relation together with internal resistance can exhibit pulses in the voltage across the junction when driven by an oscillating current source. These pulses occur singly, in pairs, triplets, etc. with a repetition rate equal to twice the driving frequency. The inclusion of capacitance and inductance generally degrades the pulse characteristics, but attainable values for tunnel junctions are tolerable, with typical parameter values, the pulses have picosecond widths. The phenomenological model becomes suspect on such time scales, however, because typical gap frequencies are just under 10/sup 12/Hz. Preliminary studies based on the microscopic tunnel-junction theory nevertheless show results qualitatively similar to those of the Phenomenological model. The effects of resistor noise and current noise have also been studied. It is concluded that well developed ps voltage pulses can be created in physical Josephson junctions.         Author Index (1976)    No author information available Summary: Not available

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