Cryopump

Abstract

A cryopump comprising: a vessel comprising a radiation shield having a frontal opening, said frontal opening forming an inlet to said vessel; a frontal array thermally coupled to said radiation shield and mounted across said frontal opening; a cryopanel structure mounted within said vessel; a two stage refrigerator extending into said vessel, a first stage of said refrigerator being thermally coupled to said radiation shield and a colder second stage of said refrigerator being thermally coupled to said cryopanel structure; wherein said vessel comprises an elongate vessel a distance between a surface of said cryopanel structure closest to said frontal opening and a surface of said frontal array closest to said cryopanel structure comprising between 0.6 and 1.2 times the diameter of said frontal opening.

1 . A cryopump comprising:
 a vessel comprising a radiation shield having a frontal opening, said frontal opening forming an inlet to said vessel;   a frontal array thermally coupled to said radiation shield and mounted across said frontal opening;   a cryopanel structure mounted within said vessel;   a two stage refrigerator extending into said vessel, a first stage of said refrigerator being thermally coupled to said radiation shield and a colder second stage of said refrigerator being thermally coupled to said cryopanel structure; wherein   said vessel comprises an elongate vessel a distance between a surface of said cryopanel structure closest to said frontal opening and a surface of said frontal array closest to said cryopanel structure comprising between 0.6 and 1.2 times the diameter of said frontal opening.   
     
     
         2 . The cryopump according to  claim 1 , wherein said distance is between 0.7 and 0.9 times the diameter of said frontal opening. 
     
     
         3 . The cryopump according to  claim 1 , wherein the diameter of the frontal opening is between 20 and 21 cm (7.8 and 8.2 inches) and said distance between said cryopanel structure and said frontal array is between 12 cm and 25 cm (4.7 and 10 inches). 
     
     
         4 . The cryopump according to  claim 1 , wherein said second stage of said two stage refrigerator is configured to maintain a temperature of said cryopanels to below 9K. 
     
     
         5 . The cryopump according to  claim 1 , wherein said frontal array comprises a disk element and an annular element, said disk element and said annular element being mounted axially displaced from each other said annular element being mounted to be closer to said frontal opening than said disk element, a diameter of said disk element being equal to or greater than a diameter of the aperture in said annular element and smaller than an outer diameter of said annular element, said outer diameter of said annular element being equal to or greater than a diameter of said frontal opening. 
     
     
         6 . The cryopump according to  claim 5 , wherein said frontal array comprises an axially extending cylindrically-shaped element, said cylindrically-shaped element connecting said disk element and annular element, said cylindrically-shaped element comprising a cylindrical surface, said cylindrical surface comprising a plurality of apertures.