Fermilab Accumulator Ring Ultra-High Vacuum System

An average pressure of 3 x 10{sup -10} Torr is required in order to store a beam of antiprotons (for up to 20 hours) in the Fermilab Accumulator Ring. The Accumulator Ring has a circumference of 474 m and consists of 114 main magnets which surround a continuous, stainless-steel vacuum chamber with a mean diameter of 12 cm. The Accumulator Ring is located in a below-grade tunnel which is inaccessible during normal operation. Consequently, all monitoring and control operations must be done remotely. In this paper the authors describe: (1) the rationale of the Accumulator Ring's vacuum system; (2) the specific choice of pumping systems (roughing, ion and sublimation) that was selected for implementation; (3) the details of the instrumentation, control and backeout systems (300 C) for monitoring the pressure and desorbing the vacuum chamber; and (4) the operating experience and performance of the entire system