Behavior of a 4K-GM Cryocooler in a Magnetic Field

The behavior of a 4K-GM (Gifford-McMahon) cryocooler in a magnetic field has been investigated. Characteristics of the magnetic regenerator materials were researched. The specific heat of ErNi0.9Co0.1, ferromagnetic regenerator material decreased under a magnetic field of 1T, while that of HoCu2, an antiferromagnetic regenerator material, had little effect of the field. The SRDK-408BW 4K-GM cryocooler, made by Sumitomo Heavy Industries, Ltd., was installed in a cryocooler-cooled superconducting magnet. The cryocooler was operated in a magnetic field under 1T. The cryocooler with ErNi0.9Co0.1 rose to its reachable temperature after increasing the magnetic field. In contrast to ErNi0.9Co0.1, the cryocooler with HoCu2 has a constant cooling capacity under 1T.