Helium Liquefaction by Gifford-McMahon Cycle Cryogenic Refrigerator

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.