Cornell Electron Storage Ring phase-III interaction region vacuum chamber

Two 115 in. long copper ultrahigh vacuum (UHV) chambers for the Cornell Ele ctron Storage Ring (CESR) interaction region were fabricated. These chamber s are a part of the phase-III upgrade project for the CESR storage ring. Th ey incorporate several novel features including a remotely engaging differe ntially pumped Viton O ring sealed UHV flange, two rf shielded bellows join ts, and inner stepped masking for synchrotron radiation. The fabrication of these chambers incorporates multistage electron beam welding to maintain t he strict tolerance required for installation through superconducting and p ermanent quadrupole magnets. Before final welding, a series of electron bea m welding setup tests were done to work out a welding procedure for optimiz ing the welding parameters and avoiding contamination in the weld zone. In this article we will describe the design, fabrication, welding, leak checki ng, and final UHV performance testing of these chambers. (C) 2001 American Vacuum Society.