Investigation on a J-T cooler used to couple with a pulse tube cryocooler.

The closed-cycle J-T cooler has been widely used in long-term missions, but as the temperature goes down, it gains the disadvantages of lower efficiency, lower reliability and higher complexity. An effective solution is to couple the J-T cooler with a pulse tube cryocooler. This study aims at the cooling temperature of 4 K with the hybrid system. A thermodynamic model of the J-T cooler precooled by a three stage cryocooler is developed and the working principles of the components are analyzed. The research shows the cooling capacity is always positively related to the lowest cooling temperature. The cooling capacity is determined by the compressor, aftercooler and the heat sinks, while the cooling temperature is mainly affected by the heat exchangers and throttling device. An experimental system is designed as well, and the next work is on the way.