A 600mW@20 K thermally-coupled two-stage pulse tube precooler for space 4 K JT cryocooler reaches high efficiency with double-inlet phase shifter

The suitable cryogenic environment is a necessary condition for ensuring the high precision and high sensitivity operation of space exploration equipment. The two-stage pulse tube cryocooler (PTC) is the basis for the normal operation of space exploration equipment working in the liquid hydrogen temperature range and cryogenic systems such as the Joule-Thomson cryocooler (JTC) that requires pre-cooling in the liquid hydrogen temperature range. Based on the pre-cooling requirements of ⁴He JTC developed by our laboratory, a high efficiency thermally-coupled two-stage PTC utilizing double-inlet phase shifter and pure SS screen filling is designed, manufactured, and tested with an eye toward space applications. Under a total electric power of 185 W, a cooling capacity of 647 mW@20 K was obtained, resulting in a maximum relative Carnot efficiency (rCOP) of 4.90 %, which met the design target. In addition, the cooling characteristics and temperature stability of the PTC were tested.