Experimental Investigation of 4.5°K Small Refrigerator

Abstract

This paper describes the design and performance of 4.5°K closed-cycle refrigerator.Using a Gifford-McMahon cycle refrigerator (manufactured by Cryomech Inc.) for cooling helium gas down to 16°K, the addition of a Joule-Thomson expansion circuit provides 1 watt (using Cryomech GB 02 refrigerator, without LN2), and 1.6 watts (using Cryomech GB 12 refrigerator, with LN2) of refrigeration power at 4.5°K.Performance is shown in Table 1.The refrigerators feature (1) to be automatic, maintenancefree and compact size, which can run continuously for about 3, 000 hours without operator, (2) to have a high efficient small heat exchangers, (3) to have a simple thermal switch to make short the cool-down time by automatically precooling the low temperature parts, (4) to have a fixed J-T valve and an automatic by-pass valve.