Cryogenic refrigerator and magnetic shield

摘要

The cryogenic refrigerator includes a two-stage cooling stage 72, a two-stage cylinder 51 provided with the two-stage cooling stage 72 at the end, and a magnetic regenerator 60b, and the two-stage cylinder 51 can be reciprocated in the two-stage cylinder 51. A housed two-stage displacer 52 and a magnetic shield 70 installed on the two-stage cooling stage 72 and extending outside the two-stage cylinder 51 along the two-stage cylinder 51 are provided. The magnetic shield 70 is formed of a normal conductor, and the product of the electric conductivity in the temperature region of 10K or less and the thickness of the magnetic shield 70 is 60 MS (mega siemens) or more and 1980 MS or less.