| 摘要 |
PROBLEM TO BE SOLVED: To suppress evaporating of a liquid helium simultaneously when suppressing a temperature rise of a low-temperature part in the case of removing impurities. SOLUTION: The cryostatic refrigerator comprises a JT refrigerating unit 20 for generating a cryostatic by Joule-Thomson expanding a high pressure helium gas, and a precooling refrigerating unit 30 for precooling a high pressure helium gas to the unit 20. In this case, supply piping 70 for reversely supplying a helium gas discharged from compressors 21, 22 of the unit 20 to a high pressure passage 41 of a first heat exchanger 40 to remove impurities of the passage 41 is provided. Heaters H1, H2, H3 for heating the gas are provided. Further, return piping 71 for returning the gas flowing through the exchanger 40 to the compressors 21, 22 is provided. An adsorber 72 is provided in the piping 71.
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