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1966     Front Cover (1966)    No author information available Summary: Not available         Table of Contents (1966)    No author information available Summary: Not available         Some Fundamentals of Superconductivity    T.G. Berlincourt Summary: Superconductivity provides the most efficient means known to man for generating high magnetic fields. It is also the basis for the most sensitive detector of weak magnetic fields and the most sensitive detector of electromagnetic radiation in the far infrared region. In addition, superconductivity holds promise for advanced computer applications. The principal aim of this conference is the elucidation of such practical applications. My own assignment is to discuss some of the underlying fundamentals as an introduction to the talks that are to follow. I will begin with a few historical comments, making only scant mention of the microscopic aspects of superconductivity.         Critical Properties of Superconducting Materials of Technological Importance    A. Paskin Summary: Most reviews of superconducting materials concentrate on analyzing ideal superconductors in terms of ideal calculations. As most of the technological properties of superconductors depend on their nonideal or irreversible behavior, this review is devoted more to presenting the ideas and the vocabulary that are now used to elucidate the critical superconducting properties relevant to the superconducting technology. Emphasis will be given to four critical properties in irreversible type II superconductors.         Some Remarks on Superconductivity    P.W. McDaniel Summary: Because of the dependence upon strong and complex magnet; fields to contain and control reacting thermonuclear plasmas in an, practical fusion reactor, the AEC took immediate interest in the 1959 Bell Telephone Laboratory developments in magnetically hard superconductors. At that time it was decided to place the emphasis in the AEC program on fundamentals of superconductivity and superconducting materials, with the expectation that industry, following its usual pattern, would develop the technology of magnet design and fabrication. Subsequently, the rapidly developing needs of the high energy physics program and recognition of the potential cost savings to be achieved by using superconducting magnets in that program have acted as a spur to considerable expansion of our efforts in superconducting magnet technology also. At present, we are spending more than two million dollars in each sector of this exciting field.         Superconducting Ultrahigh-Q Tunable Radio-frequency Filter    F.R. Arams Summary: This paper describes the application of superconductivity to the problem of reducing radio-frequency interference (RFI). Others at Airborne Instruments Laboratory who contributed to this work include K. Siegel, D. Kornfeld, E. Sard, and J. Fradkin. Selectivity is normally obtained in communications receivers by narrowing the IF bandwidth by means of a fixed-frequency crystal filter. This approach becomes ineffective where strong interfering signals, particularly those closely spaced in frequency, generate third-order intermodulation or cross modulation in the rf stages or in the mixer. Ever-increasing signal densities place more emphasis on RF1 suppression than noise factor as the prime obstruction to signal readability.         High Q Cavities - Design and Application to Measurement of Material Properties and Communications    W.H. Hartwig Summary: The improvement in Q possible in the superconducting mode exceeds 3 orders of magnitude and may reach 5 orders with good design. In the range 10 to 1000 MHz the configuration for best geometry shifts from a lumped L-C circuit, through helical resonators, to re-entrant cavities with quarter-wave TEM-mode stubs. The highest Q's are obtained with true cavities at higher frequencies, since the geometry is most favorable. To keep an economical size for a liquid helium bath some compromise in geometry is often necessary.         Superconducting Parametric Amplifiers    P. Bura Summary: Two basic phenomena underlie parametric amplification with superconductors. They are (1) variation of penetration depth with current or magnetic field and (2) motion of vortices or variation in magnetization of type II superconductors. The first of these can be called a Meissner mode, since magnetic field is excluded from the metal except for the penetration depth layer. In the second, or Abrikosov, mode, fluxoids penetrate the superconductor and are vibrating under the influence of Lorentz force at microwave frequencies.         Josephson Junction Physics and Weak Junction Magnetometry    A.H. Silver Summary: Ideally, a Josephson tunneling junction consists of two superconductors separated by a nonsuperconductor such that the current density is given by j = j/sub C/ sin /spl gamma/, where j/sub C/ is the critical current density and /spl gamma/ = h/sup -1//spl int/2mv/spl middot/ dl evaluated across the junction is the line integral the electron pair mechanical momentum. For one or more such junctions in a superconducting ring the fluxoid quantization reduces to /spl Sigma//sub i//spl gamma//sub i/ + 2/spl pi//spl Phi///spl PHi//sub 0/ = 2/spl pi/k, where /spl Sigma = /spl phi/ A /spl middot/ dl is the magnetic flux in the circuit, /spl Phi/sub 0/ = h/2e = 2.07 x l0/sup -l5/ webers, k is an integer, and the index i designates the junctions. For two such junctions the maximum total supercurrent that can be supported by the two junctions in parallel is I= /spl int/sub s/j/sub c/(r) sin y(r) /spl middot/ dS, the Fourier transform of the spatial variation of j/subc/(r), and becomes I = I/sub 0/ cos (/spl pi//spl Phi///spl Phi/sub 0/). Because of the smallness of /spl Phi/sub 0/, the maximum supercurrent of such a configuration can be used as a galvanometer of high sensitivity.         A Review of Cryotron Amplifiers    J.L. Mundy Summary: Templeton and De Vrooman and Van Baarle were among the first to use the cryotron for amplification. In their work the cryotron is ted as a switch to modulate a dc input signal. The signal level is then ,increased above the input noise of room-temperature amplifiers with a transformer. Pickup noise is the main drawback to this scheme, but, through clever balancing, minimum detectable voltages of 10/sup -11/ V have been achieved.         Hybrid Cryotron Technology    D.L. Peltzer Summary: The cryotron is a superconducting switching device usually formed by thin-film deposition in vacuum. Hybrid cryotron technology combines film deposition through stencil masks with selective etching techniques to produce arrays of interconnected cryotrons. Use of the stencil masks allows arrays to be formed in a single evacuation of a vacuum system with reliable interlayer electrical contacts and low production costs. Photoresistive techniques are used to etch the many closely spaced controls and interconnections of the array.         Cryotron Fabrication    J.P. Pritchard Jr Summary: The cryotron thin-film superconductive device may be readily employed to perform digital logic and storage functions. However, the base cost of providing a controlled cryogenic environment for operation limits its commercial potential to very large-capacity data-processing applications, e.g., a combined gate and/or bit storage count > 10/sup6/. The lossless properties of superconductive signal paths and availability of diamagnetic shielding permit practical consideration of data processors having a device count > 10/sup 9/.         Josephson Switches    J. Marisoo Summary: Josephson junctions have previously been used as gaussmeters and as microwave sources. This paper describes another application, that of a switch or logic element. The operation of the device is based on the existence of two tunnel- ing states for the Josephson junction and the fact that the transition from one state to the other is controllable with an external magnetic field.         Cryotron Memory Cells    A.R. Sass Summary: A survey of the technology of cryotron memory cells is complicated by the various forms of multiloop, persistent current cells that have been designed for the storage and readout of an information bit. In order to examine the subject it is convenient to restrict this presentation to persistent current cells of a single loop whose gate is the gate of a crossed-film cryotron (CFC) and whose read current is the control of the cryotron. The destructive read-write operation of such a cell is examined in terms of the control current-gate current phase diagram of a CFC. NDRO using the magnetic field of the persistent current to switch a “detect” gate into the normal state is examined and its limitations are discussed. The basic analogies between the cryotron cell and a magnetic core are pointed out.         Flux Pumps and Superconducting dc Generators    D.L. Atherton Summary: Flux pumps are power supplies that operate within the cryogenic environment required for superconducting magnets. One variety uses a cryogenic current step-up transformer and reactor power cryotrons, others are varieties of superconducting dynamos. Early flux pumps used superconducting pistons and thermally operated flux valves.         The Place of Superconducting Magnets in Over-All Magnet Technology    W.F. Gauster Summary: In any given situation, the choice of the appropriate type of magnet (water-cooled magnet coils for continuous duty with and without iron, long and short pulse coils, cryogenic and superconducting magnet coils) depends strongly on the desired field strength and working diameter. Using these two quantities as the variables, Bruce D. Montgomery developed an interesting graph (IEEE Spectrum 3, p. 8, Aug. 1966) showing the ranges of the recommended use of the various magnet types. In this presentation, which considers the expected future development of the over-all magnet technology, the dominant magnet type is by far the superconducting magnet coil.         Niobium-Tin Composite Tape Magnets    C.H. Rosner Summary: The utilization of Nb/sub 3/Sn, which still has the highest known critical temperature-critical current and magnetic field combination for construction of high-field superconductive magnets, has so far not been widespread, and relatively few supermagnets exceeding 100 kG are ir use today. Continued efforts since the early 1960’s have led to the development of several practical types of conductors based on either the diffusion process or a vapor deposition method. Emphasis on flexibility and reusability of superconductive materials has resulted in the availability of high-field conductors that can be handled with minimum care; the use of thin layers of Nb/sub 3/Sn circumvents the stress limitations often associated with intermetallic compounds.         Plasma-Plated Nb/sub 3/Sn Coils    D.A. Haid Summary: Plasma-plating is a technique that permits the rapid construction of high-field niobium-tin superconducting magnets without the costly intermediate step of preparing the intermetallic compound in the form of wire or strip. This talk outlines the general procedures followed in plating helical windings and describes the design, construction, and operation of a 2-in.-bore, 70-kG test magnet. Also mentioned are those operational features that directly contributed to the flexibility permitted the design engineer - the ability to vary the conductor cross section throughout the coil, to utilize various materials of construction, and to employ other superconducting materials, such as NbZr and V/sub 3/Si.         Ti-Nb Magnets    C.N. Whetstone Summary: Total thermal stability for copper-superconductor composites is observed below the nucleate to film boiling transition. In this regic transition and recovery currents are independent of the superconducting critical temperature and depend only on the heat transfer properties of metals to liquid helium. Operation just below the nucleate to film boiling transition takes advantage of the increased cooling, and thus higher stabilized current densities can be supported. At the lower fields there is a copper limited region which is completely determined by the maximum nucleate boiling flux. In this region stabilized currents are inversely proportional to the square root of the copper resistivity. For higher fields, there is a superconductor limited region in which critical currents follow a superconducting short sample curve at slightly elevated temperatures. The temperature of the composite conductor was measured in the copper limited region with use of carbon thermometry. In this region the temperature rise is 0.66/spl deg/K and is identified with the nucleate to film boiling transition. In the superconductor limited region at the higher fields, currents are lower, and temperature rises approach zero as the composite curve approacheshort sample values at 4.2/spl deg/ K.         Inorganic Insulated NbZr and NbTi Solenoids    R. Hintz Summary: Thus far, work at Berkeley has concentrated on small superconducting solenoids with high current density. These magnets are being used for nuclear alignment and adiabatic demagnetization. Currently they are being wound with no insulation on the copper-plated wire. This results in a coil that is strongly shorted turn-to-turn. However, the coils are carefully insulated layer-to-layer with a tightly woven Fiberglas cloth. These magnets can be charged conveniently, have produced high current densities, and can be safely carried through the transition from the superconducting to the normal state.         A Large Model MHD Magnet    Z.J.J. Stekly Summary: A large, stabilized, MHD-type superconducting magnet was built to demonstrate the feasibility of this type of magnet for central station MHD power generation. The magnet windings are formed in a saddle shape, required to produce a field perpendicular to the magnet bore. The bore of the lgnet is 12 in., in which the field is uniform for about 4 ft. The overall length of the magnet assembly (including structure) is 120 in., and the outside diameter is 54 in.         A Low-Temperature Electron Microscope with High-Field Superconducting Lenses    H. Fernandez-Moran Summary: Results from an extension of earlier work are described which were obtained with different types of cryoelectron microscopes using highfield, niobium-zirconium solenoid lenses with specially designed cryogenic specimen stage assemblies, pole pieces, and superconducting regulating circuitry. Exceptional long-term stability and high quality of electron microscopic images directly recorded at magnifications or 200 to 20,000 were demonstrated under carefully controlled cond. tions, operating in persistent current mode at 4 to 32 kG and 4 to 50kV accelerating potential. Electron micrographs of biological specimens were recorded at liquid helium temperature (4.2/spl deg/K) with a superconducting Nb-Zr objective lens of special design. Resolutions of 10 to 20 /spl Aring/, were reproducibly attained, particularly in specimens of catalase crystals embedded in thin layers of heavy metals. These exhibited exceptional contrast and anomalous transparency phenomena. Preliminary experiments have also demonstrated characteristic electron optical phenomena associated with trapped fluxes in thin superconducting film.         Cabled Magnets    H. Brechna Summary: The work reported is based on partially and fully stabilized cabled coils with various cooling configurations. When cooling was enhanced, either by providing cooling channels around the cable or by pressurizing the liquid helium through a coil, the heat transfer coefficient was found to exceed 0.4 W/cm/sup2/ in coils with a bore 3 in. in diameter and 6 in. in length for currents up to 800 A and central fields up to 35 kG.         Argonne National Laboratory 12-ft Hydrogen Bubble Chamber Superconducting Magnet    J.R. Purcell Summary: The design for a large, superconducting split-coil system in the Argonne National Laboratory’s 12-ft -i.d. hydrogen bubble chamber has been considered at length. Iron is to be used in any event for magnetic shielding, and a complete magnet design incorporating a stabilized conductor and a self-contained refrigeration system has evolved. The design problems are discussed and the proposed system is described. The reasons for the choice of the composite conductor configuration are given, and some of the conductor characteristics are described.         Brookhaven National Laboratory 14-ft Bubble Chamber Magnet    A.G. Prodel Summary: A comparison is made between a conventional copper-iron 20-kG magnet for the BNL 14-ft bubble chamber and the 30-kG, 14-ft superconducting magnet designed for this facility. Design parameters for the superconducting magnet are discussed. Experimental results of the effects of stress on the resistivities of copper and aluminum are presented. Details of the superconducting magnet conductor configuration, magnet coil assembly, and magnet assembly are given.         Hybrid Magnets    J. Williams Summary: A hybrid magnet is defined to be a combination of a water-cooled copper magnet and a superconducting magnet. The purpose of the combined use of these systems is the exploitation of the advantages of each individual system and the minimization of their disadvantages. The water-cooled copper magnet is inexpensive in construction and flexible in use and is capable of generating a field of any strength, subject only to the limit of available power. However, the power required for the generation of high fields is very great. For instance, 200 kG in 2 in. bore requires 10 MW. Furthermore, the outer sections of a conentional magnet generate less magnetic field per watt than do the inner sections.         An Alternator with Superconducting Field and Room-temperature Armature    H.H. Woodson Summary: Initial studies of the use of superconductors in rotating machines showed that ac losses and viscous losses at low temperature require so much additional refrigeration that it is more attractive to operate superconductors only on direct current and in stationary fields. This still allows considerable gain because superconductors produce higher flux densities than copper and iron, and no iron is required in the magnetic circuit. Consequently more space is available for active armature conductors. These two advantages, higher field strength and more room for armature conductors, indicate improvements in alternator size and weight, especially in machine sizes greater than about 50 kW.         Energy Storage in Superconducting Coils    E.J. Lucas Summary: To investigate the problems associated with the use of superconducting coils in pulsed energy storage devices, two coil systems were built. The first system made use of a single-layer coil having an inductance of 8.35 mH. This coil was wound with a stabilized superconductor composed of nine Nb-25% Zr 0.010-in.-diam wires imbedded in a 0.040 x0.5-in. copper substrate. The coil was constructed by edge bending this conductor on a 4-in. radius.         Energy Storage in Flux Tubes    D.A. Haid Summary: Plasma-plating is aptly suited to the construction of inductive energy storage devices possessing low inductance, high discharge current, and unlimited storage time. Advantages and disadvantages of superconducting low inductance storage are discussed.         Generation of Electrical Pulses with Superconductors    G.K. Gaule Summary: Electrical energy in the form of short, steep pulses of large currents (1000 A and higher) at high voltages (1000 V and higher) is needed to drive pulsed transmitters, pulsed high field magnets, plasma discharges and pulsed light sources, and in similar applications in nuclear physic and other fields. If the pulse rate required is moderate, the average power requirements can be fulfilled by a small, continuously operating power source which merely "charges" a storage device from which the pulse energy is drawn. In most conventional designs, the storage function is performed by large capacitors. It had been known that inductors could store electrical energy in an analogous fashion, but inductive storage became a practical goal only with the advent of high-field, high-current superconductors, which permit the storage of large (> 5 k J) energies in systems of less bulk and weight than the conventional ones. While an extremely high field is not essential for inductive storage, parameters leading to a high inductance at a given (high) current and to satisfactory msec-pulse or "high frequency" properties are being explored. Loss-free operation between pulses in the "persistent" mode is possible with a superconducting switch short-circuiting the solenoid. For this, a high current (160 A and higher) superconducting relay switch was developed.         Some Remarks on Superconductive ac Power Transmission    D.C. Freeman Jr Summary: Thermal losses in superconductive power transmission lines (exclusive of dissipation in the superconductor and charging current losses) can be overcome by about 1.2% of the power line capacity for long, high-capacity (> 1000 mVA) lines. This is substantially less than the electrical losses in conventional EHV transmission lines. On a capital cost basis, estimates indicate that the cryogenic line refrigeration and installation requirements can be met with an investment per kilowattyear which compares very favorably with those for conventional long, high-capacity EHV lines - provided again that zero line power dissipation is assumed.         A Review of Low Temperature Transmission Lines and Transformers    S.H. Minnich Summary: Perennial speculation exists on the advantages of applying cryogenics to electrical apparatus, such as transformers, and to underground transmission. A number of design conditions must be satisfied if this is to be done. For transformers, the iron cannot be refrigerated; hence the windings must be kept separate. In high-capacity transformers, the leakage flux densities are probably too high for the use of soft superconductors. Hence, normal conductors or hard superconductors must be used. Considerations of eddy current losses indicate the need for fine strands and transposed conductors. If these are used, the losses in hard superconductors are substantially equal to those in normal conductors. Hence, high-conductivity normal conductors operating at hydrogen temperatures are preferred. Potential highvoltage capability of liquid hydrogen is also an advantage. Substantial theoretical gains in power densities and reduction in over-all losses can be calculated, and indicate the need for continuing work in this area.         Applications of Superconductivity to Active Space Shielding    E.D. Hoag Summary: A continuing program sponsored by the National Aeronautics and Space Administration, George C. Marshall Space Flight Center, Huntsville, Alabama, is being carried on at the Avco Everett Research Laboratory to study active radiation shielding for space vehicles. This program encompasses a broad range of topics, including theoretical and experimental studies on active shielding concepts as well as supporting work on superconducting magnet technology needed to implement these concepts.         Superconducting Gyroscope Systems    K.F. Schoch Summary: Superconducting gyroscope development was begun because the use of superconducting magnetic bearings, together with gyro operation in the cryogenic environment, offered the possibility of avoiding random changes in drift behavior which limit the accuracy of conventional gyros. This development has been supported to a varying degree by NASA, the Air Force, and the Navy. NASA has supported work at the Jet Propulsion Laboratory and the General Electric Company. The Air Force has supported work at Minneapolis-Honeywell and also at General Electric.         Application of Superconducting Magnets to a Thermonuclear Rocket    G.W. Englert Summary: An analytical evaluation was made of a conceptual thermonuclear rocket. The energy source of the rocket was a reaction volume confined by a magnetic mirror system in which one mirror was slightly weaker than the other. A stream of high-energy helium-3 and deuterium ions is emitted from the weaker mirror, providing a small amount of thrust at a very high specific impulse. The thrust can be increased sufficiently to make this system of interest for interplanetary travel by the addition of a hydrogen propellant. This additional propulsion mass is injected in the path of the escaping high-energy reactor particles. The reactor particles transfer energy to a portion of the hydogen and ionize it. The ionized portion could be quite effectively accelerated by the gradient of the magnetic field already provided by the local mirror magnet. This process was studied in detail by the method given in NASA TN D-3656.         Magnetic Fields for Beam Handling and Accelerators    P.G. Kruger Summary: Conventional quadrupole lenses provide magnetic fields of about 20 kG and magnetic field gradients of about 2 or 3 kG/cm. On the other hand, it is well known that Nb/sub 3/-Sn will operate satisfactorily up to 200 kG, and that magnetic field gradients of at least 25 kG/cm can be achieved’ with this material. Furthermore, since the approximate focal length of a quadrupole lens system is proportional to (BR/(db/dr))/sup 2/, where BR is the magnetic rigidity of the particle to be focused, it seems attractive to try to make a quadrupole lens by using current-sheets of Nb/sub 3/-Sn, so that dB/dr is as large as possible. Under these circumstances one will have a smaller focal length for a lens system and a correspondingly larger angular aperture than that provided by conventional quadrupole lens systems.         Superconducting Accelerator Development at the University of Illinois    A.O. Hanson Summary: In examining possible proposals for replacing our present accelerators, we can consider the AGS synchrotron and the FFAG betatron, but these cannot reach a full 100% duty factor. The machines that can effectively reach unit duty factor and are most attractive to us are the CW linac and the microtron using superconducting cavities such as are under development at Stanford. We would require only small currents but want the ultimate in energy resolution, 0.1% or better.         Superconducting Accelerator Design    P.B. Wilson Summary: The application of superconductivity to accelerators has been considered in several previous papers. At Stanford University, activity has been directed principally toward the development of a superconducting electron linear accelerator with unity duty cycie. In addition to a large gain in duty cycle over present pulsed machines, other advantages may well result from steady-state operation, such as better energy resolution and greater stability through the use of feedback systems. The rf losses to be expected in a superconducting linac can be estimated by using the results of measurements that have been ma on test cavities.         Application of Superconductivity to Electron Microscopy    E.D. Klema and J.M. Donhowe Summary: The use of superconducting magnets for lenses has already been shown to be potentially of great importance to electron microscopy. Such lenses provide extreme stability of the magnetic field with time along with low power requirements. As these magnets are developed specifically for electron microscope lenses in the future, they will surely be incorporated into new units, especially in the case of high-energy electron microscopes.         List of Registrants (1966)    No author information available Summary: Not available

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