Properties of kinetic inductances of superconducting fine filaments and thin films are reviewed and discussed. When the thickness of films or diameter of fine filaments are smaller than magnetic field penetration depth of superconductors, higher field is required for vortex (flux quantum) penetration into fine filament superconductors. In such cases, effect of kinetic inductance can be observed. The possibility of energy storage systems by kinetic inductance are discussed and the maximum storage energy density of kinetic inductances is estimated to be two orders smaller than that of electro-magnetic inductances. But the energy and inductance per unit volume of kinetic inductances are estimated to be several orders larger than that of electro-magnetic inductances. The applications of kinetic inductances are also discussed and integrated kinetic inductance for electronics and small scale energy storage systems are proposed. The properties of effective flux in kinetic inductance are also discussed. It is pointed out that the effect of kinetic inductance may become important in fine filament composite superconductors and high Tc superconducting thin films.
There is no disturbance-free superconducting coil. The disturbance gives the temperature rise of the superconductor, and the normal transition occurs when the temperature of the conductor exceeds its current sharing temperature. If the superconducting coil is stabilized adequately in some way, the normal zone does not appear, or the created normal zone disappears by itself. But if not, the normal zone propagates and the coilgets to quench. When a superconducting coil is used in some system, it is to be designed as a reliable and stable coil so as not to raise quench and not to lower the efficiency of the system operation. High stability can be achieved by giving a lot of coolant in the coil and giving a large amount of substrate to the superconductor, both of which lower the compactness or the performance of the coil. In order to get stable and compact superconducting coils, many stabilization methods have been thought out. In this paper, major cryogenic stabilization methods are explained and the problem about magnetic instabilities in superconductors is not discussed assuming that finemulti-filamentary strands are used as constituents of the conductors.
With the intention of identifying a quench position in a superconducting coil, the behaviour of an artificially quenched superconducting coil has been investigated. The superconducting coil is a solenoidal, bobbinless, and tightly wound impregnated coil with many voltage terminals, thermocouples, and heaters. The propagation of a normal zone is made two-dimensional by a one-turn-heater or three-dimensional by a point-heater set in the coil. The time-varying terminal voltages and temperatures in the coil have been in detail examined with respect to quench positions, i.e., locations of the heaters. Normal front velocities and effective thermal conductivities of the radial, azimuthal, and axial directions are also analyzed from those experimental results.
A quench simulation program has been developed with the intention of identifying a quench position in a superconducting coil and it has been applied to behaviour analysis of an artificially quenched superconducting coil. The superconducting coil is a solenoidal, bobbin-less, and tightly wound impregnated coil with many voltage terminals, thermocouples, and heaters. The propagation of a normal zone was made two-dimensional by a one-turn-heater or three-dimensional by a point-heater set in the coil. The time-spatial changes in terminal voltages and temperatures agree well with those obtained from the previous experiment within an accuracy of ±10ms or ±1mm. If accurate thermal properties of the materials constituting the superconducting coil are obtained, identification of the quench position in the coil should be possible.
This paper describes the principal design features and performance test results of a three-stage Gifford-McMahon cycle cryogenic refrigerator by which we have achieved no-load temperature of 3.3K and succeeded in helium liquefaction. The refrigeration capacity was 20mW at 4.2K and the helium liquefaction rate was 10cm3/h. The keypoint of the success is the selection of GdRh and Gd0.5Er0.5Rh compounds as a regenerator material. This is the first success that regenerative cycle cryogenic refrigerator has liquefied helium without auxiliary refrigerator for precooling.