Development of 1 K Refrigerator Using 0.1 W GM Cryocooler

Abstract

We have succeeded in developing a 1 K refrigerator by a cascade method with 4 K pot (plate) and 1 K pot, using the smallest commercially available 4 K GM cryocooler (0.1 W @ 4.2 K). Since the 0.1 W refrigerator has a low cooling power, in order to liquefy 4 He gas, not only sufficient heat radiation prevention but also pressurization of 4 He gas exceeding about 5 atm is required. In addition to the normal arrangement with the cold head of the refrigerator at the bottom, we have succeeded in realizing a 1 K environment in the inverted arrangement as well.