Abstract: A method for operating a cryocooler includes: connecting a second compressor in series with a first compressor on a high pressure line or a low pressure line; connecting a buffer volume to the low pressure line via a supply valve; executing initial cooling for cooling an expander from an initial temperature to a cryogenic temperature in a state where the second compressor and the buffer volume are connected to the cryocooler; and executing a steady operation of maintaining the expander at the cryogenic temperature after the initial cooling. The execution of the initial cooling includes supplying a working gas to the expander by using the first compressor and the second compressor, and controlling the supply valve to keep a pressure of the high pressure line within a preset appropriate pressure range based on the measured pressure of the high pressure line.

Abstract: A cryocooler includes: an expander capable of executing initial cooling for cooling from an initial temperature to a cryogenic temperature and a steady operation of maintaining the cryogenic temperature subsequent to the initial cooling; a high pressure line which is connected to the expander and through which a working gas taken into the expander flows; a low pressure line which is connected to the expander and through which a working gas exhausted from the expander flows; a pressure sensor that measures a pressure of the high pressure line; a buffer volume for storing the working gas; a supply valve that connects the buffer volume to the low pressure line; and a controller that controls the supply valve during the initial cooling based on the pressure of the high pressure line measured by the pressure sensor to keep the pressure of the high pressure line within a preset pressure range.

Abstract: A cryocooler includes an expander that includes a cooling stage, an exhaust temperature sensor that measures an exhaust temperature which is a temperature of a working gas exhausted from the expander and outputs an exhaust temperature signal indicating the measured exhaust temperature, and a controller that compares, during execution of initial cooling in which the cooling stage is cooled from an initial temperature to a cryogenic temperature, the measured exhaust temperature to a reference temperature based on the exhaust temperature signal and completes the initial cooling in a case where a temperature difference between the measured exhaust temperature and the reference temperature is within a reference range.

Abstract: A cryocooler includes an expander that includes a cooling stage, an exhaust temperature sensor that measures an exhaust temperature which is a temperature of a working gas exhausted from the expander and outputs an exhaust temperature signal indicating the measured exhaust temperature, and a controller that compares, during execution of initial cooling in which the cooling stage is cooled from an initial temperature to a cryogenic temperature, the measured exhaust temperature to a reference temperature based on the exhaust temperature signal and completes the initial cooling in a case where a temperature difference between the measured exhaust temperature and the reference temperature is within a reference range.