The vacuum system for the PEP II High Energy Ring straight sections

The six straight insertions of the PEP II High Energy Ring (HER) serve various functions: lattice tuning, beam injection and abort, providing space for RF cavities, longitudinal and transverse feedback, beam diagnostics and the interaction point. A stainless steel vacuum system has been designed; prototypes are currently being built. Cooling is required due to radiation coming from the last arc dipole and resistive losses in the vacuum chamber. Although the nominal beam current of the HER is 1 A the vacuum system is designed for 3 A to provide margin and an upgrade path.