Design of the vacuum system for the high energy ring of an asymmetric B-factory based on PEP

The multi-ampere current required for high-luminosity operation of an asymmetric B factory lads to extremely stressing requirements on a vacuum system suitable for maintaining long beam-gas lifetimes and acceptable background levels in the detector. The authors present the design for a Cu alloy vacuum chamber and its associated pumping system for the 9-GeV electron storage ring of the proposed B factory based on the Positron-Electron Project (PEP). The excellent thermal and photodesorption properties of Cu make it possible to handle the high photon flux in a conventional, single-chamber design with distributed ion pumps. The X-ray opacity of the Cu is sufficiently high that no additional lead shielding is necessary to protect the dipoles from the intense synchrotron radiation generated by the beam. The design allows chamber commissioning in <500 hr of operation.<>