A Static Magnetic Refrigerator for Superfluid Helium with New Heat Switches and a Superconducting Pulse Coil

Abstract

A new magnetic refrigerator is proposed which can produce and preserve superfluid helium with high reliability and efficiency. This paper describes the design of the refrigerator and presents the results of experimental tests using a model refrigerator. The refrigerator is designed to give a Carnot cycle in a temperature range of 1.8–4.2 K. Gadolinium gallium garnet (GGG) is employed as the working substance, and new heat switches which have no moving parts and make use of differences in the heat transfer rates in the various heat transfer modes of a fluid are used. The working substance is magnetized and demagnetized by means of a superconducting pulse coil. A useful cooling power of about 0.6 W was obtained at 1.80 K. The calculated and experimental results verify that the magnetic refrigerator can, in principle, stably and continuously produce and maintain superfluid helium.