Characteristics of a 4 K Gifford–McMahon cryocooler using the Gd2O2S regenerator material

In order to improve the cooling power at 4.2 K, performance of a Gifford–McMahon cryocooler was investigated. We focus on regenerator materials and structure of 2nd stage regenerator. A ceramics regenerator of Gd2O2S (GOS) was used in the cold part of the 2nd stage regenerator. To utilize the GOS effectively, we applied a layered structure to the 2nd stage regenerator. It was divided into three parts along the length for the temperature distribution, to which lead (Pb), HoCu2 and GOS spheres were filled. The cooling power improved to 0.22 W at 4.2 K. The electric power consumption is 1.3 kW. When only Pb and HoCu2 (without the GOS) are filled, the cooling power is 0.15 W at 4.2 K. The experimental results show that GOS is very effective to increase the cooling power at 4.2 K.