Hybrid cryogenic vacuum pump apparatus and method of operation

Abstract

Apparatus for vacuum pumping an enclosed chamber without the use of activated charcoal to remove hydrogen by cryosorption. As a result, the potential for contamination by a sorbent material is eliminated. The pumping structure includes an integral two-stage vacuum pump. The first-stage pump is a cryogenic pump having a pump chamber and cryoarrays mounted on an expander for cryocondensation of the principal gases present in the vacuum chamber. The second-stage pump operates at room temperatures and includes one or more getter pumps whose principal function is to remove hydrogen molecules that may be present in the vacuum chamber after the first-stage cryopump has removed most of the cryocondensable gases from the vacuum chamber. In one aspect of the invention, the first-stage pump is separated from the second-stage pump by a gate valve to protect the getter pumps during the regeneration flushing of nitrogen through the first-stage cryogenic pump chamber. In another aspect of the invention, a technique is disclosed to eliminate the need for a gate valve separating the two pumps. In another aspect of the invention, an ion pump is added to the two-stage vacuum pump to reduce the helium and neon molecules that may be present after the pumping of hydrogen and the other cryocondensable gases in the vacuum chamber.