Analysis of Rare Earth Compound Regenerators Operating at 4 K

This paper describes the analysis of regenerators which consist of rare earth compounds. In a regenerative cycle refrigerator, refrigeration loss is larger than useful refrigeration capacity at liquid helium temperature, and the main loss is regenerator loss. The purpose of this paper is to establish a numerical calculation method which gives useful information for designing high efficiency regenerators. The model regenerator consisted of two regenerator compounds: Er3Ni, which is hot-side material, and another material such as ErNi2, Er0.75Dy0.25Ni2, ErNi, or Er0.9Yb0.1Ni. The regenerator efficiency was calculated for various ratios of the two materials. Regenerator efficiencies for various combinations of rare earth compounds are systematically discussed. The maximum regenerator efficiency was obtained at 4 K with the condition that Er3Ni was 45% and Er0.9Yb0.1Ni was 55% of the regenerator volume. Moreover, it was shown that a refrigerator with this optimized regenerator could achieve a 52% larger refrigeration capacity than one with an all-Er3Ni regenerator.