Cryopump and method of operating the cryopump

Abstract

A cryopump includes a high-temperature cryopanel, a low-temperature cryopanel, and a cooling system. The cooling system has: a refrigerator provided with a first stage for cooling the high-temperature cryopanel and a second stage for cooling the low-temperature cryopanel; and a control unit configured to control a cool-down operation in which the first stage and the second stage are cooled in order to initiate a vacuum pumping operation of the cryopump. The cooling system may be configured to selectively provide a cooling relief effect to the first stage at least temporarily in the cool-down operation.

What is claimed is: 
     
         1 . A cryopump comprising:
 a high-temperature cryopanel;   a low-temperature cryopanel; and   a cooling system comprising:   a refrigerator comprising a high-temperature stage for cooling the high-temperature cryopanel and a low-temperature stage for cooling the low-temperature cryopanel; and   a control unit configured to control a cool-down operation in which the high-temperature stage and the low-temperature stage are cooled in order to initiate a vacuum pumping operation of the cryopump, wherein   the cooling system is configured to provide a cooling relief effect selectively to the high-temperature stage at least temporarily during the cool-down operation.   
     
     
         2 . The cryopump according to  claim 1 , wherein
 the cooling system is configured to supply an operating gas, having a temperature higher than that in the vacuum pumping operation, to the high-temperature stage at least temporarily during the cool-down operation.   
     
     
         3 . The cryopump according to  claim 1 , further comprising:
 a heat load generating element configured to provide a heat load to the high-temperature stage.   
     
     
         4 . The cryopump according to  claim 1 , wherein
 the cooling system is configured to control the cool-down operation to include an initial cooling phase in which temperatures of the high-temperature stage and the low-temperature stage are lowered toward respective target temperatures,   the cooling system is configured to provide the cooling relief effect selectively to the high-temperature stage at least temporarily during the initial cooling phase.   
     
     
         5 . The cryopump according to  claim 1 , wherein
 the cooling system is configured to control the cool-down operation to include, subsequent to an initial cooling phase, a temperature adjustment phase in which temperatures of the high-temperature stage and the low-temperature stage are adjusted to respective target temperatures, and when the initial cooling phase is terminated, the low-temperature stage is cooled to a temperature higher than its target temperature,   the control unit is configured to control a heat cycle frequency in the refrigerator so as to cool the high-temperature stage to its target temperature in the temperature adjustment phase,   the cooling system is configured to provide the cooling relief effect selectively to the high-temperature stage at least temporarily during the temperature adjustment phase.   
     
     
         6 . A method of operating a cryopump comprising:
 cooling a cryopanel from an initial temperature higher than a cryogenic temperature for a vacuum pumping operation to the cryogenic temperature by using a refrigerator; and   after the cooling, initiating the vacuum pumping operation, wherein   the cooling includes providing a cooling relief effect selectively to a high-temperature stage of the refrigerator.