Investigation of a 1.6 K Space Cryocooler for Cooling the Superconducting Nanowire Single Photon Detectors

The superconducting nanowire single photon detectors (SNSPD) are now widely used in space quantum communication, satellite laser ranging, and quantum key distribution, etc. However, a very low temperature around 2 K is required for its operation and performance improvement. We are developing a 1.6 K hybrid cryocooler to meet this demand, which is composed of a three-stage Stirling-type pulse tube cryocooler (SPTC) and a Joule-Thomson cryocooler (JTC). The hybrid cryocooler has no moving component at the cold end and is driven by the long life linear compressor, thus realizing high reliability, low vibration and long operation life time. The cryogenic system, including the coupling structure with the SNSPD, is descripted in detail. The thermodynamic enthalpy analysis of the last-stage of the hybrid cryocooler is carried out, by which the upstream pressure and precooling temperature are optimized to meet the required base temperature and cooling capacity with less input power. The model is described and the experiments coupling with a SNSPD simulated load are carried out. The results show that the hybrid cryocooler can achieve 16.3 mW at 1.6 K, 20 mW at 1.8 K and 25 mW at 2.1 K, respectively, and thus suggests a promising space cryocooler for cooling the SNSPDs.