The purpose of this study is to improve the cooling capacity of a two-stage Gifford-McMahon (GM) cryocooler at 4.2 K. We focus on regenerator materials of 2nd-stage regenerator. One of the demanded factors for regenerator materials is a high specific heat at the using temperatures. From the point of view, ceramic material, Gd2O2S (GOS), has very attractive property around 4 K. However, effective temperature range of the specific heat of the GOS is narrow. Therefore, we adopted layered structure to the 2nd-stage regenerator. From the experimental results, the cooling power at 4.2 K achieves 0.21 W using the GOS regenerator material. That volumetric ratios of 2nd-stage regenerator are Pb:HoCu2:GOS = 40:30:20. When filling the regenerator materials of Pb and HoCu2 (the volumetric ratios are Pb:HoCu2 = 40:60), the cooling power at 4.2 K is 0.15 W. The results show that the cooling power is 40 % improved using the GOS material.
GM cryocooler
Gd2O2S regenerator material