Abstract: The invention relates to a device (21) for avoiding the memory effect in cryogenic pumps having a first cooling stage (23) and a second cooling stage (25) which adjoins the first cooling stage (23) in the axial direction. A cylindrical shield (31) has an opening (37) and a base (35), which base (35) is penetrated centrally by the two-stage cooling head (21) in such a way that the first cooling stage (23) is arranged outside the shield (31) and the second cooling stage (25) is arranged within the shield (31). An intermediate chamber (34) is formed between the shield (31) and the first cooling stage (23), and the base of the shield (31) is connected in a thermally conductive manner to the first cooling stage (23) by means of a thermal bridge (33). A cooling panel (43) which serves as pumping surface is connected to the second cooling stage (25) and is provided within the shield (31).

Abstract: The invention relates to a device (21) for avoiding the memory effect in cryogenic pumps having a first cooling stage (23) and a second cooling stage (25) which adjoins the first cooling stage (23) in the axial direction. A cylindrical shield (31) has an opening (37) and a base (35), which base (35) is penetrated centrally by the two-stage cooling head (21) in such a way that the first cooling stage (23) is arranged outside the shield (31) and the second cooling stage (25) is arranged within the shield (31). An intermediate chamber (34) is formed between the shield (31) and the first cooling stage (23), and the base of the shield (31) is connected in a thermally conductive manner to the first cooling stage (23) by means of a thermal bridge (33). A cooling panel (43) which serves as pumping surface is connected to the second cooling stage (25) and is provided within the shield (31).

Abstract: A cryopump includes a housing in which is mounted a cooling head having a first, 80.degree. K. cooling stage and a second, 20.degree. K. cooling stage. A shield mounted on the cooling head surrounds the two stages, and a cooling surface within the housing and within the shield surrounds the second stage. The housing and the shield include corresponding inlet openings for admitting gases, and a diaphragm protects the cooling surface from heat radiation entering the inlet openings. The diaphragm is closer to the cooling surface than is the shield, creating a transfer opening that permits free access of gases into the volume within the shield. The cooling head can be rotated by an adjustment motor to displace the shield inlet opening with respect to the housing inlet opening to control the suction capacity of the pump for process gases without the need for an additional reduction valve, while maintaining the capacity for processing water vapor.

Abstract: A seal for vacuum flange connections includes a plastically deformable seal ing and an associated ring designed to ensure that the seal remains tight even upon cooling after a previous heating. This is obtained by providing a support ring having two resilient retaining portions, each for one plastically deformable seal ring. The design makes it possible to repeatedly use and re-use seal rings, which preferably are made of metal for example, gold.