Cryopumps and inlet flow restrictors for cryopumps

Abstract

A flow restrictor for restricting a flow rate of gas flowing into a cryopump and the cryopump are disclosed. The flow restrictor is configured to be mounted in an inlet of the cryopump, the flow restrictor comprising: an inlet component for providing a gas flow path into the cryopump; a shielding plate mounted to at least partially obscure the gas flow path though the inlet component; and an intermediate component linking the shielding plate to the inlet component, the intermediate component comprising at least one aperture, the at least one aperture defining at least one gas flow path into the cryopump The shielding plate is configured to shield the gas flow path through the inlet component such that when mounted on the cryopump there is no direct line of sight path through the inlet component to a cryopanel within the cryopump.

1 . A flow restrictor for restricting a flow rate of gas flowing into a cryopump, said flow restrictor being configured to be mounted in an inlet of said cryopump, said flow restrictor comprising:
 an inlet component for providing a gas flow path into said cryopump;   a shielding plate mounted to at least partially obscure said gas flow path though said inlet component; and   an intermediate component linking said shielding plate to said inlet component, said intermediate component comprising at least one aperture, said at least one aperture defining at least one gas flow path into said cryopump;   
       wherein
 said shielding plate is configured to shield said gas flow path through said inlet component such that when mounted on said cryopump there is no direct line of sight path through said inlet component to a cryopanel within said cryopump. 
 
     
     
         2 . The flow restrictor according to  claim 1 , wherein said inlet component has an annular form delimiting an orifice, said orifice defining said gas flow path. 
     
     
         3 . The flow restrictor according to  claim 1 , wherein said intermediate component comprises a plurality of apertures. 
     
     
         4 . The flow restrictor according to  claim 1 , wherein a surface of said intermediate component comprising said at least one aperture lies at an angle of between 120° and 60° to said shielding plate 
     
     
         5 . The flow restrictor according to  claim 4 , wherein said surface of said intermediate component comprising said at least one aperture is substantially perpendicular to said shielding plate. 
     
     
         6 . The flow restrictor according to  claim 1 , wherein said intermediate component comprises a cylinder. 
     
     
         7 . The flow restrictor according to  claim 1 , wherein an outer periphery of said inlet component extends beyond an outer periphery of said shielding plate. 
     
     
         8 . The flow restrictor according to  claim 7 , wherein an outer periphery of said shielding plate extends beyond a perimeter of said orifice of said inlet component. 
     
     
         9 . The flow restrictor according to  claim 1 , wherein said shielding plate and said inner component have a substantially circular outer perimeter. 
     
     
         10 . The flow restrictor according to  claim 1 , wherein said at least one aperture of said intermediate component is configured to restrict flow into said cryopump to a predetermined flow rate. 
     
     
         11 . A cryopump comprising:
 a pump inlet;   a refrigeration unit;   a cryopanel configured to be cooled by said refrigeration unit; and   a flow restrictor according to  claim 1 , said flow restrictor being mounted in an inlet of said cryopump such that said flow restrictor restricts a flow of gas into said inlet.   
     
     
         12 . A method of upgrading a cryopump comprising:
 removing a throttle plate mounted across an inlet of said cryopump for limiting flow into said cryopump; and   replacing said throttle plate with a flow restrictor according to  claim 1 .