Vacuum chamber of the injector synchrotron for the Advanced Photon Source

The 40 chambers of the 368 m, 7-GeV injector synchrotron of the Advanced Photon Source are made from 1 mm-thick, 316 LN stainless steel tubing. Tubes are cold-drawn to an elliptical shape with inside major and minor axes of 6 cm and 3.7 cm, respectively. This results in a thin metallic chamber without corrugations, which allows maximum beam space in the magnets and withstands atmospheric pressure. Sections of the chamber are bent to match the radius of curvature (33.3 m) of the beam over the entire effective length of the dipole magnets. A modified orbital welder is used to join sections of tubing. The chambers and the pumping system required to achieve a pressure of 10-9 Torr are described. A straight section of chamber tubing was tested under external pressure up to 60 psig. At 15 psig, the resulting deflection at the minor half axis was 0.2 mm and a maximum compressive stress of 13,500 psi was measured. Tube deformation remained in the elastic region up to ∼ 38 psig