A 4.0°K Single-Engine Cycle Helium Refrigerator

Abstract

Claude-cycle helium refrigerators have in the past used two or more expansion engines, or a single expander in conjunction with liquid nitrogen precooling, to provide refrigeration[^1,2]. This paper describes a new modified Claude-cycle helium refrigerator, in which a single reciprocating expansion engine is the sole source of refrigeration, Refrigeration capacity is at least 1 W at 4.0°K, with additional refrigeration at 30° K. available for heat stationing. After initial system charging and clean-up, operation of the refrigerator is completely automatic, both for cooldowa and for steady-state operation. The system was designed to provide for redundancy of the expander and/or compressor, with automatic switchover in case of component degradation. That is, a spare component can be installed in the system, ready for immediate use when required. Where redundancy is not required, the system can be operated at full load without a redundant expander or compressor.