Multi-Stage Pulse Tube Refrigerator for Temperatures below 4 K

This paper describes the experimental results of multi-stage pulse tube refrigerators with novel staging configuration. Based on a previous study of the multiple staging configuration for the pulse tubes and the characteristics of the pulse tube operated at liquid helium temperature, a three-stage pulse tube refrigerator was fabricated and tested. Pressure oscillation was generated by a valved compressor generally used for G-M cryocoolers. A lowest temperature of 3.6 K has been achieved by this system. The performance of the regenerative tube inserted between the hot end of the third stage pulse tube and its phase shifter located at room temperature has been discussed.