COMBINATION OF A CRYOPUMP AND A NONEVAPORABLE GETTER PUMP IN APPLICATIONS

A preliminary study on the pumping performance of a cryopump combined with a high-capacity non-evaporable getter (NEG) pump was performed. T he pumping speed, the pump-down time, and the gas composition in a sta ndard UHV chamber were evaluated using the cryopump alone and combined with a high capacity getter pump made from sintered porous getter mat erial. In order to exploit the high specificity of the getter pump for hydrogen and water vapor, the cited quantities were measured both bef ore and after a baking treatment. It was found that the ultimate press ure in the baked chamber could be greatly improved using the getter pu mp and that pump-down times of the unbaked chamber were consistently r educed due to the very high pumping speed of NEGs for water vapor. (C) 1997 American Vacuum Society.