Cryogenic refrigerator and method of controlling cryogenic refrigerator

A cryogenic refrigerator comprising:

• an expander that generates cold by expanding a refrigerant gas in an expansion space;
• a compressor that compresses the refrigerant gas returning from the expansion space of the expander;
• pipes that are connected to the expansion space of the expander and the compressor and circulate the refrigerant gas between the expansion space of the expander and the compressor, the pipes including a high-pressure pipe in which a high-pressure refrigerant gas flows toward the expansion space of the expander from the compressor and a low-pressure pipe in which a low-pressure refrigerant gas flows toward the compressor from the expansion space of the expander;
• and
• a determiner that determines whether or not a frequency of pressure change of the refrigerant gas flowing in the pipes is in a predetermined range,
• wherein the determiner comprises:
• a memory unit that prestores a switching cycle for switching between supplying and discharging of the refrigerant gas under normal operation of the cryogenic refrigerator,
• a pressure acquisition unit that acquires pressure data of the refrigerant gas in a predetermined time interval and accumulates the pressure data in the memory unit,
• a cycle acquisition unit that analyzes the pressure data of the refrigerant gas accumulated in the memory unit and derives the frequency of pressure change, and
• a comparison unit that reads out the switching cycle from the memory unit and determines whether or not the frequency of pressure change is in the predetermined range.