Search

Eddy current losses in conducting plates placed in a non-uniform alternating magnetic field at cryogenic temperatures have been calculated taking into account temperature dependencies of resistivity, heat capacity and heat-transfer coefficient. The calculation method is based on a coupled solution of a quasi-stationary electromagnetic problem and a non-stationary heat-conduction equation. A simplification of the task is achieved by neglecting eddy current reaction and free space charge. In this case the problem is solved in two stages: 1) the calculation of electromagnetic field; 2) the determination of a temperature distribution in the plate. As the first boundary condition for heat-conduction equation it is assumed that the heat transfer from edges of the plate equals zero. The second boundary condition is determined as a solution of the integral equation describing the law of conservation of energy relevant to the plate. The nonlinear two-dimensional heat conduction equation has been solved using partition of coordinates, implicit difference approximation and modified Thomas algorithm for obtained finite-difference equations. The numerical results remain in a good agreement with data obtained by means of an experimental model of the cryogenic device, while neglecting of thermal processes results in substantial errors amounting up to several hundreds percent.

Power systems requiring power levels as high as a few megawatts to a few gigawatts for periods of several microseconds to several milliseconds with repetitive frequencies of a few hertz to a few kilohertz are being considered for potential space applications. The impulsive nature of the power presents the opportunity to use inductive energy storage techniques for pulse duty to enhance economic and practical considerations. An inductor must be efficient, lightweight, and reliable, and it must have high energy density if it is to be used in space based power systems. Cryogenic inductors are best suited for such an application. Parametric analyses of the two potential types of cryogenic inductors (superconducting and hyperconducting) reveal that the hyperconducting (high purity aluminum) inductor would be significantly lighter and achieve higher energy densities without the added penalty of a helium refrigeration system, thus resulting in improved overall system reliability. The lightweight hyperconducting cryogenic inductor technology is, however, in its infancy. This paper describes the required technology base which would allow the eventual application of the lightweight cryogenic inductor in space power systems, and also conclusively demonstrates the underlying principles.

The design, construction and testing results of the superconducting magnet system for a molecular tritium circulation source are presented. The system is used for electron antineutrino mass measuring experiments by tritium [Beta]-decay spectrum analysis. There are 13 superconducting tritium source solenoids, as well as 4 spectrometer magnets cooled by a two-phase helium mixture circulating through a 100 watt refrigerator. The temperature of the magnets is 4.5 to 4.8 K at 0.6 to 0.7 torr. The total cold mass is about 600 kg.

The present paper analyses effect of thermal processes on eddy-current losses in construction elements of cryogenic and superconducting devices. Maxwell's equations coupled with heat-conduction equation are solved with taking into account the dependence of resistivity, heat capacity and heat-transfer coefficient on temperature. Analysis of losses as a function of magnetic field, frequency and geometry factors is given for the case of thin strip in a uniform magnetic field. It is shown that losses calculated with taking into account the thermal processes may differ from those obtained at constant temperature.