Interaction Region Vacuum System Design at the Pep-ii B Factory

The Interaction Region Vacuum System in the PEPII B-Factory at SLAC must produce average pressures in the 10 Torr range. Low beamline pressures will minimize the background radiation encountered by the BaBar Detector. A combination of copper and stainless steel vacuum chambers with continuous antechambers are used to make up the beam tubes. Linear Non-Evaporable Getter (NEG) pumps are used to produce distributed pumping along the length of these beam tubes. High conductance "microwave" type screens provide RF shields between the beam aperture and the NEG pumps. In this paper the design features of the beam tubes, NEG pumps, and RF pump screens are described and the vacuum and impedance analyses conducted in support of the design are discussed.