386 mW/20 K single-stage Stirling-type pulse tube cryocooler

•A single-stage Stirling-type multi-bypass pulse tube cryocooler has been built and tested.•The lowest no-load temperature is 15.5 K.•A cooling capacity of 386 mW/20 K can be achieved with the input power of 246 W.

Recently, we reported a single-stage Stirling-type pulse tube cryocooler (SPTC) that achieved a no-load temperature of 18.6 K and 0.2 W/20.6 K with 268 W input power at the frequency of 38 Hz. By further optimizing the regenerator, using the stainless steel screens only, a new SPTC driven by a dual-opposed linear compressor has been built and tested. At present, a lowest temperature of 15.5 K, which is a new record for single-stage SPTC, and 386 mW/20 K cooling power can be achieved with 246 W input power, which is comparable to the two-stage SPTC with a similar input power. The optimization process of regenerator will be presented in this paper. Experimental results indicate that it is important for SPTC to reduce the flow resistance of regenerator at the warm end and enhance the regenerative capacity of the cold end to improve the cooling performance. Lead spheres were also employed as part of the regenerator to achieve the possible lower temperature, but the test results show that there is no evident improvement in achieving lower temperature.