Performance study on a two-stage 4 K pulse tube cooler

Systematic investigations towards performance improvement of a two-stage 4 K pulse tube cooler, concerning structural parameters, staging configuration and compressor input power, are presented in this paper. Theoretical analysis and experiment reveal that a proper negative DC now through the double-inlet bypass has positive effects on cooling performance. With a modified cooler design a highest cooling power of 0.5 W at 4.2 K and 1 W at 5 K have been achieved. With heating load of 20 W at 67 K on the first stage, the 2nd stage can provide 0.42 W at 4.2 K. All these results have been obtained by using a 6 kW G-M compressor combined with a redesigned GM rotary valve. By using a compressor with measured input power of 1.7 kW the same cooler has a net cooling power of 170 mW at 4.2 K. The corresponding COP at 4.2 K is 1.0x10(-4), which reaches the same order of magnitude as that of GM or GM+JT coolers at the same temperature range.