High Enthalpy Materials for Use in Superconductor Stabilization and in Low Temperature Cryocooler Regenerators

Abstract

At helium temperatures the heat capacity of most materials becomes very small. Materials which undergo phase transitions at low temperature may, however, show anomalies in the specific heat making it one or two orders of magnitude higher than in normal metals. Such materials are of technical interest for superconductor stabiliztion or regenerative refrigeration. We present some metallic materials with very high specific heat anomalies due to various kinds of phase transitions and Schottky effects. A magnetic field up to 7 Tesla does not influence their heat capacity significantly. We report different possibilities of using these substances for superconductor stabilization, and show our first results. Regenerative gas-cycle refrigerators with usual regenerators cease operation below about 15 K because the heat capacity of the regenerator material becomes smaller than that of the helium working fluid. New materials with very high specific heats in this low temperature range are proposed.