Cooling Capacity Characteristics of Low Power Consumption （2 kW Class） 4 K-GM Cryocoolers

From the COP （Coefficient of Performance） equation, there are two ways to improve cooling efficiency cryocoolers: （1） increasing capacity, and （2） decreasing electrical input power. In recent years, we have focused on possibility method for a 4 K-GM （Gifford-McMahon） cryocooler. this paper, 7 kW class compressor, which is commonly connected cold head, was replaced with low power consumption （2 class） compressor. The experiments achieved measured capacity 0.95 W at 4.2 K head reciprocation speed 36 rpm compressor 1.9 kW. calculated relative Carnot were 5.0×10-4 3.5 %, respectively. A reciprocating selected secure sufficient expansion work in second space. This an effective by