Demonstration of a 10K Stirling cooler for space applications

The performance capability of a two-stage Stirling cycle cooler intended for space applications in the range of 10 K has been demonstrated and characterised over a range of interface temperatures. To achieve the desired performance, several design improvements were made to an existing qualified cooler, originally intended for application in the 20-50 K range. The modifications have extended the ability of the cooler to provide 45 mW of heat lift at 10.4 K, with a base temperature at 9.4 K. Significant advances have been made despite the inherent limitations of regenerator material heat capacity and the constraints of Carnot efficiency at these low cryogenic temperatures. Background information is provided on the closed cycle mechanical cooler with an outline of the design, including a summary of the developments to improve regenerator performance, compressor capacity and reduction of parasitic heat losses in the system. Results of recent characterisation testing are presented herein. These results are compared with calculated performance from modeling, and reviewed in light of design improvements that are proposed to further reduce the base temperature and increase heat lift of the cooler accordingly.