Helium liquefaction by a Gifford–McMahon cycle cryogenic refrigerator

Abstract

This article describes the principal design features and performance test results of a three-stage Gifford–McMahon cycle cryogenic refrigerator by which the authors have achieved a no-load temperature of 3.3 K and succeeded in helium liquefaction. The refrigeration capacity was 20 mW at 4.2 K and the helium liquefaction rate was 10 cm3/h. The key point of the success is the selection of GdxEr1−xRh compounds as a regenerator material. This is the first time that a Gifford–McMahon refrigerator has liquefied helium without the use of a Joule–Thomson stage.