Pressure burst free high capacity cryopump

A cryopump comprising:

• a vacuum vessel;
• a refrigerator having at least a first stage and a second stage;
• a radiation shield mounted within the vacuum vessel and enclosing second stage cryopumping surfaces, the radiation shield and the second stage cryopumping surfaces configured to be cooled by the refrigerator of the cryopump, the radiation shield comprising:
• a housing including a primary opening, an end opposite the primary opening, and a lateral side wall connected to the end, a frontal array being across the primary opening and the housing having an inner surface facing the second stage cryopumping surfaces and having an interior volume sufficient to hold the second stage cryopumping surfaces, the second stage cryopumping surfaces including primary second stage condensing surfaces and non-primary second stage condensing surfaces;
• a drain hole located in a center region of the end of the housing to permit cryogenic liquid and gas to traverse therethrough during a regeneration operation, the drain hole providing for fluid communication between the interior volume of the housing and an annular space between the vacuum vessel and the radiation shield;
• and
• a baffle:
• (a) directly connected to the inner surface of the end of the radiation shield housing to extend across the drain hole and to cover the drain hole, wherein the baffle and the inner surface of the end of the radiation shield housing define a channel having two ends, the drain hole being in fluid communication with the channel at a location between the two ends and (b) configured to direct gases traversing through the drain hole away from the non-primary second stage condensing surfaces.