Analysis and Tests of Hybrid Start-up Process of a Space Dilution Refrigeration Unit

Abstract Space dilution refrigerators for space applications have evolved over the past thirty years. The microgravity condition makes the helium isotope fluid flow and mix difficult in space. The surface tension of capillaries replaces gravity in the space dilution refrigerators, resulting in a different operating process compared with that of the ground systems. The start-up process of the space dilution refrigeration unit with a high pre-cooling temperature is carefully analyzed and tested. The dilution unit starts successfully and obtains 162 mK at a flow rate of 4 mL/min 3 He and 50 mL/min 4 He. The operating conditions and the phase interface location are carefully discussed for the performance and optimization based on the experimental results.