The Stanford Two-Mile Linear Accelerator Vacuum System

The vacuum system of the Stanford two-mile linear accelerator has been designed as nominally a "very high" vacuum system operating in the 10-6 to 10-8 torr region. Main vacuum pumps are of the getter-ion type; the pumps are connected to an allmetal system fabricated of stainless steel except for viton "O" rings in the valve seats. The accelerator structure evacuated by this system consists of OFHC copper rectangular and disk-loaded waveguides with stainless steel flanges connecting the various portions of the structure. For completeness, a brief description of the vacuum system for the beam switchyard at the end of the accelerator is included because it is an integral part of the overall system. Conventional diffusion pumps are used to maintain pressures of 10-4 to 10-5 torr, i. e., nominally "high" vacuum.