CRYOCOOLER AND OPERATION METHOD OF CRYOCOOLER

摘要

In a cryocooler 1 which generates a coldness having 4 [K] or lower by expanding helium, an expander 50 expands high-pressure helium. A compressor 12 compresses low-pressure helium returned from the expander 50, generates high-pressure helium, and supplies the high-pressure helium to the expander 50. When a temperature of helium in the expander 50 is 2.17 [K] or lower, the pressure of the low-pressure helium is equal to or higher than a pressure of a curve in which a volumetric thermal expansion coefficient of helium is 0 in a state diagram of helium in which a horizontal axis is temperature and a vertical axis is pressure.