Ultra high vacuum cryopump relief valve assembly

摘要

A secondary pressure relief valve assembly is coupled to a cryopump relief valve for reducing the gas load on the cryopump. The pressure relief valve assembly comprises a main housing mounted to a crypoump exhaust conduit enclosing that portion of the cryopump valve typically exposed to the external environment. A second relief valve is mounted to the main housing and operates in series with the cryopump valve to exhaust pressurized gases from the cryopump during regeneration. A pump is coupled to a port on the main housing and maintains a pressure within the main housing which is less than the pressure of the external environment. As such, the pressure differential across the cyropump valve is reduced. Since the leakage and permeation gas loads are linearly related to the pressure differential, they are correspondingly reduced.