Cryopumping for Cyclotrons

High pumping speeds and high pumping capacities are required for the vacuum systems of large cyclotrons. Only cryopumps and getter pumps safely provide these features. The best pumping system for a particular machine can be designed only upon fixing size, operating pressure, pumpdown time, mechanical design and materials of the latter. The criteria for the selection of the pumps are discussed here and the solutions adopted for a few existing machines reviewed. The vacuum design and performance of VICKSI, which makes use of condensation cryopumps developed at CERN, are described in detail.