Ion Pump Operation on a 5.5 MeV and 12 MeV Van de Graaff Accelerator

An improved vacuum system, using combined Ion and Cryo-pumping techniques has been successfully used on Van de Graaff accelerator beam tubes. The pumping through-put of the Ion pumps has proved more than adequate in handling tube discharges. Base pressures are in the mid 10-7 torr range, while operating pressures have been improved by factors of 2-9 over Hg. diffusion pumped systems. System maintenance has been virtually eliminated. This paper describes Ion pump starting techniques, roughing systems and characteristic operation of Ion pumping and combined Ion and Cryo-pumping on a C.N. and E.N. accelerator.