Development of a Magnetic Refrigerator Operating between 2 K and 10 K
A prototype adiabatic demagnetization refrigerator (ADR) operating between 2 K and 10 K has been built and tested. The refrigerant for the ADR is Gadolinium Gallium Garnet (GGG). In the design thick slices of single-crystal GGG are sandwiched together with strips of high-purity copper. The copper strips are used to transfer heat between the GGG and the 2 K and the 10 K heat switches. The heat switches employed in the ADR have no moving parts. The 10 K heat switch is a helium gas-gap heat switch; while, the 2 K heat switch is a He II-gap heat switch. Preliminary tests indicate that the prototype ADR can provide 27 mW of cooling at 2 K for 165 s; where, the cycle period is 12.6 minutes. The efficiency of the ADR relative to Carnot is 25%. Methods for improving the efficiency of the system are discussed.
KeywordsEntropy Helium Epoxy Gallium Gadolinium
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