Investigations on a 1 K hybrid cryocooler composed of a four-stage Stirling-type pulse tube cryocooler and a Joule-Thomson cooler. Part A: Theoretical analyses and modeling

Abstract

This paper conducts systematic theoretical analyses of a hybrid cryocooler composed of a four-stage Stirling-type pulse tube cryocooler (SPTC) and a Joule-Thomson cooler (JTC), in which the former provides the necessary precooling powers to the latter which aims at reaching a temperature of 1.0 K. The structural design of the hybrid cryocooler is described and its working mechanism focused on. Both enthalpy flow and mass flow rate models are developed and then combined to study the cooling performance. The ideal gross cooling capacity and its changing characteristics with both the last stage precooling temperature and the upstream pressure are elaborated. It is found that the optimal last stage precooling temperature provided by the four-stage SPTC should be around 8.0 K with the optimal upstream pressure of 0.36 MPa to maximize the gross cooling capacity of the hybrid cryocooler at the aimed temperature. Finally, the heat exchanger efficiency of the JTC is considered to study the hybrid cryocooler performance close to the real situation. Given the last stage heat exchanger efficiency of 97%, with He-4 in the four-stage SPTC and He-3 in the JTC, a cooling power of 14.7 mW at 1.0 K can be achieved. The results indicate that the suggested hybrid cryocooler would become a promising candidate for cooling the superconducting nanowire single photon detector (SNSPD) for the potential applications in the next-generation space quantum information technology.