Intermediate cooling from pulse tube and regenerator in a 4Â K pulse tube cryocooler

This paper introduces intermediate cooling by thermally attaching heat exchangers on the second stage pulse tube and regenerator in a commercial 4 K pulse tube cryocooler. Due to the large enthalpy flow in the 2nd stage pulse tube and regenerator, both intermediate heat exchangers on the pulse tube and regenerator can provide cooling capacities in the temperature range of 5-15 K without or with minor effect on the performance of the 4 K stage. Extracting cooling capacity from the pulse tube or regenerator reduces the 1st stage cooling performance in the present study. The joint intermediate heat exchanger on the pulse tube and regenerator has demonstrated promising results for applications.