Vacuum system of the third-generation synchrotron light source at SRRC

The SRRC 1.3 GeV electron storage ring was designed as a third-generation synchrotron light source. Aluminum alloys were adopted as the materials of the ring vacuum chambers. The anti-chamber structure with a 'concentrated + distributed ion pump' pumping configuration effectively removed the desorbed gas molecules in the bending chamber. A computer program was devised to simulate the distribution of the outgassing rate in the storage ring. It was shown that the arrangement of the pumps, according to the simulation, was effective to reduce the average pressure. An oil-free machining method with complete oil-free pumping configuration resulted in the reduction of the hydrocarbon contamination on the surface of the chamber. The welding and installation work were performed in a clean room or dust-controlled area so that little dust trapping was observed during the machine operation. The desorbed gases were mainly hydrogen molecules, which had less effect on the beam lifetime. An accumulated beam dose of >80 A·h was quickly achieved and the pressure rise per electron beam current (dP/dI) was reduced by three orders of magnitude in a short time period of normal operation. (author)