A high capacity completely closed-cycle 250 mK ~3He refrigeration system based on a pulse tube cooler

摘要

We present the design of a completely closed-cycle refrigeration system. The system consists of four stages; the first two, 40.5 and 2.7 K, are provided by a pulse tube cooler, the third and fourth stages by helium adsorption refrigerators. The adsorption refrigerators use ~4He and ~3He with base temperatures of 700 and 250 mK, respectively. Performance tests including some with the cooler rotated from the vertical showed that with a load of 15 mu K. a temperature below 286 mK can be maintained for 72 h.