Pulse tube cryocooler and method for cooling down pulse tube cryocooler

Abstract

A pulse tube cryocooler includes a cold head including a pulse tube and a radiator thermally coupled to a high-temperature end of the pulse tube, and a forced cooler that forcedly cools the radiator in a cool-down operation of the pulse tube cryocooler from an ambient temperature to a cryogenic temperature.

What is claimed is: 
     
         1 . A pulse tube cryocooler comprising:
 a cold head including a pulse tube and a radiator thermally coupled to a high-temperature end of the pulse tube; and   a forced cooler configured to forcibly cool the radiator in a cool-down operation of the pulse tube cryocooler from an ambient temperature to a cryogenic temperature.   
     
     
         2 . The pulse tube cryocooler according to  claim 1 ,
 wherein the forced cooler is configured to stop forced cooling of the radiator after the cool-down operation.   
     
     
         3 . The pulse tube cryocooler according to  claim 1 ,
 wherein the forced cooler comprises:   a sensor that detects a state of the pulse tube cryocooler,   an air-cooled or liquid-cooled cooler that cools the radiator, and   a controller configured to:
 determine whether the pulse tube cryocooler is in the cool-down operation or not based on an output of the sensor, and 
 operate the air-cooled or liquid-cooled cooler in the cool-down operation. 
   
     
     
         4 . The pulse tube cryocooler according to  claim 3 ,
 wherein the sensor includes a temperature sensor provided in the cold head, and   wherein the controller is configured to:
 compare a measured temperature of the cold head measured by the temperature sensor with a temperature threshold, and 
 operate the air-cooled or liquid-cooled cooler in a case where the measured temperature of the cold head exceeds the temperature threshold. 
   
     
     
         5 . The pulse tube cryocooler according to  claim 1 ,
 wherein the forced cooler includes a cooling fan disposed separately from the cold head.   
     
     
         6 . The pulse tube cryocooler according to  claim 1 ,
 wherein at most ¼ of a total length of the pulse tube in an axial direction extends inside the radiator.   
     
     
         7 . The pulse tube cryocooler according to  claim 1 ,
 wherein the radiator includes a radiating fin that extends in an axial direction of the pulse tube, and   wherein the forced cooler includes a cooling fan disposed upward or obliquely upward of the radiating fin.   
     
     
         8 . The pulse tube cryocooler according to  claim 1 , further comprising:
 a valve unit disposed separately from the cold head and connected to the high-temperature end of the pulse tube by a pipe.   
     
     
         9 . A method for cooling down a pulse tube cryocooler that includes a cold head including a pulse tube and a radiator thermally coupled to a high-temperature end of the pulse tube, the method comprising:
 performing cool-down of the pulse tube cryocooler from an ambient temperature to a cryogenic temperature; and   forcedly cooling the radiator in the cool-down of the pulse tube cryocooler.