Development of a 2 K Joule-Thomson Cryocooler with 4He

The 2 K mechanical Joule-Thomson (JT) throttling refrigeration system is crucial for the scientific observation and quantum communication of space detectors with extremely high sensitivity and resolution, such as X-ray Microcalorimeter Spectrometer and Superconducting Nanowire Single-Photon Detectors. A 2 K-JT refrigeration system is currently under development and the operating mass is 4He. The JT cycle, precooled by a two-stage thermally coupled pulse tube cryocooler, is driven by a four-stage JT compression system. The precooler can provide 12 K and 85 K temperature zone pre-cooling at the same time. The four-stage direct current (DC) linear compressor set achieves a very low inlet pressure and a greater overall compression ratio of up to 200. The pressure drop in the low-pressure line is a very important parameter in the design of a 2 K-JT refrigeration system. Reducing the pressure drop in the low-pressure flow path of the system can effectively decrease the load on the compressor unit and facilitate the achievement of lower pressure and lower temperature at the evaporator. The design progress of the 2 K-JT refrigeration system is described in terms of integrated consideration of fluid flow and heat transfer. At present, the JT system experimental platform has been built and the corresponding performance tests are being carried out.