Cornell Electron Storage Ring phase-III interaction region vacuum chamber

Two 115 in. long copper ultrahigh vacuum (UHV) chambers for the Cornell Electron Storage Ring (CESR) interaction region were fabricated. These chambers are a part of the phase-III upgrade project for the CESR storage ring. They incorporate several novel features including a remotely engaging differentially pumped Viton O ring sealed UHV flange, two rf shielded bellows joints, and inner stepped masking for synchrotron radiation. The fabrication of these chambers incorporates multistage electron beam welding to maintain the strict tolerance required for installation through superconducting and permanent quadrupole magnets. Before final welding, a series of electron beam welding setup tests were done to work out a welding procedure for optimizing the welding parameters and avoiding contamination in the weld zone. In this article we will describe the design, fabrication, welding, leak checking, and final UHV performance testing of these chambers.