2021 年 56 巻 3 号 p. 135-141
This is a review of compact liquefaction/recondensation equipment with cryocoolers, namely, GM-coolers and pulse tube cryocoolers. The improvement of liquefaction performance is remarkable since the advent of the 4-K pulse tube cryocooler. This article describes a brief history about 4-K cryocoolers and their liquefaction performance. Additionally, commercialized helium gas liquefaction/recondensation systems with cryocoolers are introduced and those specifications are shown.