The superfluid Stirling refrigerator, a new method for cooling below 0.5 K

Abstract

A new sub-Kelvin refrigerator, the superfluid Stirling cycle refrigerator, uses a working fluid of 3He- 4He mixture in a Stirling cycle. The thermodynamically active components of the mixture are the 3He, which behaves like a Boltzmann gas, and the phonon-roton gas in the 4He. The superfluid component of the liquid is inert. Two refrigerators have been built, and temperatures of 340 mK have been achieved.