Development of 4K GM-JT Cryocooler Systems

As an example of helium gas reduction due to the high price and difficulty of obtaining helium gas in recent years, one method is to cool superconducting magnets and superconducting radio-frequency cavities, etc. directly with a small mechanical cryocooler instead of using liquid helium. In this case, since the cooling capacity per unit is small, multiple units are used in combination depending on the required cooling capacity, which causes problems in terms of power consumption （efficiency）, footprint, and maintenance costs. Therefore, we have been developing a large-capacity and high-efficiency 4KGM-JT（Gifford-McMahon-Joule-Thomson） cryocooler system in the 10 W class at 4.2 K, using our 4K-GM cryocooler as a pre-cooler. This paper describes the technical details used in this cryocooler system.