This review is devoted to the physics of current-carrying superconductors and normal metals having two or more stable states sustained by Joule self-heating. The creation, propagation, and localization of electrothermal domains and switching waves leading to the transition from one stable state to another in uniform and nonuniform samples are treated in detail. The connection between thermal bistability and hysteresis, dropping and stepped current-voltage characteristics, self-induced oscillations of current and voltage, selfreplication of electrothermal domains, and the formation of periodic and stochastic resistive structures are considered.

Self-heating in normal metals and superconductors

Extra AC losses for a CICC coil due to the non-uniform current distribution in the cable

The principles of operation and the design of power transformers based on superconducting shields have been considered. The laboratory prototypes of fault current-limiting and special-purpose (arc welding/furnace) transformers have been tested. The application of both low-T/sub c/ and high-T/sub c/ superconducting shields has been studied. >

Application of superconducting shields in current-limiting and special-purpose transformers

Technical magnetic properties of melt-spun (Nd1−xPrx)2Fe14B at low temperature

The influence on the propagation velocity of the normal zone of four phenomena was investigated: (1) the temperature dependence of the specific heat and the thermal conductivity; (2) the current-sharing zone; (3) the electromagnetic diffusion of current through a possible superstabilizer; and (4) the thermal diffusion through a possible insulator. At the beginning, these influences were studied independently of each other. In all cases, after a model of the particular phenomenon was created, the equations of thermal and electromagnetic behavior were solved analytically and the expressions for the propagation velocity obtained. These expressions were then put into nondimensional forms, which have allowed four correction factors to be defined that take into account the influences studied, and depend only on one or two nondimensional parameters. Subsequent studies were made to investigate how to combine these correction factors to obtain general formulas for the velocity, taking into account a part or all of these influences. A review is presented of these formulas, which are of interest for the superconducting windings where the heat transfer to helium can be neglected on the time scale of the quench process. >

General formulas for the adiabatic propagation velocity of the normal zone

Flow of helium II through porous plugs

Effects of transient heat transfer to liquid helium on steady propagation velocity of normal zones in superconducting wires

System for coil simulation measurements of losses and instabilities in superconducting wires

Influence of porous coatings on heat transfer in superfluid helium

Transient heat transfer from thin superconducting and normal wires to saturated Hell and to pressurized Hell was investigated. Rectangular current pulses of 0.5 milliseconds duration and longer were applied to the sample while voltage and current were detected with a resolution in the microsecond range. For the determination of the sample temperature the temperature characteristic of the wire resistivity was used in the case of normal conductors and the temperature characteristic of the critical current in the case of superconductors. Data are reported for bath temperatures of 2 K and, in the case of the superconducting samples, transverse magnetic fields of 1.5 T.

U. Ruppert

Papers

Flow of helium II through porous plugs

Effects of transient heat transfer to liquid helium on steady propagation velocity of normal zones in superconducting wires

System for coil simulation measurements of losses and instabilities in superconducting wires

Influence of porous coatings on heat transfer in superfluid helium

Transient Heat Transfer to Superfluid Liquid Helium