An ultrahigh vacuum application of a refrigerator‐cooled cryopump

A refrigerator‐cooled cryopump is applied to an ultrahigh vacuum system made of aluminum alloys. This system is easy to bakeout and to achieve a pressure around 2–6×10⁻⁹ Pa. A pressure in the 10⁻⁹ Pa range is obtained without the baking process being repeated, if only dry nitrogen gas, instead of air, is introduced into the vacuum chamber. Some different regeneration procedures are also studied.