DIFFERENTIAL PRESSURE ELECTRON BEAM SYSTEM, METHOD AND GUN

摘要

A differential pressure electron beam system comprising means defining at least a first vacuum enclosure (12) adapted to be maintained at a first vacuum level and a second vacuum enclosure (18) adapted to be maintained at a second vacuum level higher than the first vacuum level. An electron gun generates an electron beam within said first and second enclosures; the electron gun means includes the second vacuum enclosure. Gun mounting means mounts the electron gun for movement within said first vacuum enclosure. Valve means (98) between the first and second vacuum enclosures permits communication between the first and second enclosures when the first enclosure is being pumped, and isolates the second vacuum enclosure from the first when the second enclosure is at a higher vacuum than the first enclosure. Active pumping means pumps the first and second vacuum enclosures to the first vacuum level. Ultra-high vacuum pumping means (94) within or in communication with the second vacuum enclosure pumps only the second vacuum enclosure to said second vacuum level.