Abstract
The vacuum chamber with non-evaporable getter (NEG) film coating provides clean surface and large pumping speed after activation at high temperature in situ baking. Activation processes of NEG coated aluminum chambers (Ti-30%, Zr-30%, V-40%) have been made by baking the chamber at either 180℃ for 24h or 200℃ for 2h. The photon exposure tests are performed at the 19B1 white light beam line of 1.5GeV Taiwan Light Source to inspect the outgassing rate inside the chamber. The yield of photon stimulated desorption (η) was measured by the throughput method. A residual gas analyzer has been installed for measuring the species of gas. After activation and photon exposure for several times, the ultimate pressure of NEG coated aluminum chamber is about 4×10^(-11)Torr. The initial photon stimulated desorption rate of 2×10^(-5) molecules/photon was obtained which is about one order of magnitude lower than non-coated aluminum alloy chamber. The yield of photon stimulated desorption can reach about 1×10^(-7) molecules/photon when beam dose was more than 20Ah. The residual gases in the system are mostly the hydrogen molecules rather than methane or others. It mainly came from experimental system. However, it is found that part of methane was generated from chemical reaction at NEG film surface. The thermal outgassing of Kr had been found during activation and pressure build-up process as well.
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