GB1170824A - Rapid pump-down vacuum chambers incorporating cryopumps - Google Patents

Abstract

1,170,824. High vacuum pumps. 500 Inc. Sept.21, 1967 [Oct.27, 1966], No.43097/67. Heading F1N. A vacuum is produced rapidly in a working chamber 12 by opening a valve 20 to a cryopump 26 having a thermal mass 40,41 previously cooled to a temperature sufficiently low to allow the gases in the working chamber to condense thereon without causing the temperature of the thermal mass to rise above the maximum condensation temperature. The thermal mass 40, 41 is cooled by a refrigerator 45 operable before evacuation of the chamber 12 commences and accordingly of smaller capacity than a refrigerator required to operate only during actual evacuation. The thermal mass is preferably lead or copper plates but may be neon or high-pressure helium contained in a plurality of thin-walled stainless steel tubes (80, Fig. 5, not shown). If the thermal mass is in the plate form shown it may be cooled by liquid flowing in coils in thermal contact therewith. Refrigerator 45 had a highly cooled section 46 in thermal contact with a radiation shield 38. The shield 38 has a top plate 53 supported on inclined walls 54, the spaces therebetween affording communication to the cryopumping chamber 36. The space between the walls 35, 49 of the cryopump and radiation shield is insulated by particulate or foamed insulation or by being evacuated by a mechanical pump 42. A rough vacuum is produced in the working chamber prior to the opening of the valve 20 by a mechanical pump 15, and after operation of the cryopump 26 the residual gases are removed by a diffusion, ion or sublimation pump 18. A single cryopump 26, Fig.6 (not shown) may be connected to a number of working chambers each controlled by an individual valve (92, 93, 94).