Vacuum design for a Superconducting Mini-Collider

The phi factory (Superconducting Mini-Collider or SMC) proposed for construction at UCLA is a single storage ring with circulating currents of 2 A each of electrons and positrons. The small circumference exacerbates the difficulties of handling the gas load due to photodesorption from the chamber walls. The authors analyze the vacuum system for the phi factory to specify design choices. It is concluded that the SMC vacuum system, while more challenging than that of existing storage rings, is within the bounds of sound engineering practices. The antechamber moves the gas load away from the beam, thereby lowering the required distributed pumping. To minimize photodesorption, stainless steel backed by a Cu cooling bar has been selected for the chamber material. This design allows for chamber commissioning in approximately=300 hours of ring operation.<>