Vacuum design for the 3 GeV TPS synchrotron light source

Abstract

The 3 GeV Taiwan Photon Source (TPS) is a synchrotron light accelerator which is designed for a beam emittance of < 2 nmrad at a beom current of 400 mA. The vacuum system for the electron storage ring provides a pressure of < 1 nTorr for the electron beam with long beam life time and small disturbance from trapped ions. Due to the limited space for the pumps and the poor conductance of the beam ducts, the vacuum chambers should be manufactured with a clean surface of very low outgassing rate. Aluminum alloys vacuum chambers and the structures of confined-pumping for the localized photo-desorption are selected to meet the design requirement. The CNC-machining for the bending chambers in pure alcohol spraying, followed by ozonated water cleaning and TIG welding in clean room, provides a clean surface and simple structure which lowers the outgassing rate and the chamber impedance. Combinations of the lumped non-evaporable getters (NEG) and the sputtering ion pumps are located near the absorbers for higher efficiency of localized pumping capability. Either the NEG-strips or interior NEG-coating will be used for the Undulator chambers for providing a good linear pumping feature. The design concept will be described in this paper. Besides, the simulation of the pressure distribution and some test results of outgassing measurement for the aluminum chambers will be discussed. © 2008 IOP Publishing Ltd.