AVS 47th International Symposium
    Vacuum Technology Wednesday Sessions
       Session VT-WeM

Paper VT-WeM4
Study the Exposure Dose-Dependent Photon Stimulated Desorption Phenomena

Wednesday, October 4, 2000, 9:20 am, Room 201

Session: Sorption Processes and Leak Detection
Presenter: G.Y. Hsiung, SRRC, Taiwan
Authors: G.Y. Hsiung, SRRC, Taiwan
K.-Y. Young, Institute of Nuclear Science, NTHU, Taiwan
Y.J. Hsu, SRRC, Taiwan
J.-R. Chen, SRRC and Institute of Nuclear Science, NTHU, Taiwan
Correspondent: Click to Email
The photon stimulated desorption (PSD) is studied by using the synchrotron radiation white light of critical energy at 2.14 keV from the 1.5 GeV Taiwan Light Source (TLS). The samples of various materials, e.g. aluminum alloys, OFHC, etc. are installed in a chamber at a beam line of SRRC for exposure measurement. The sample is water cooled during the exposure to the synchrotron light that the variation of temperature on the surface is < 0.2 degree C. A quadrupole mass spectrometer is used to measure the desorbed gas molecules by PSD in the exposure chamber. The result shows a decrease of the PSD-rate for each gas after a long time exposure of photon beam on the samples. The measured photoemission yield on the sample during exposure also decreases. The curves of pressure rise of each PSD-gas versus the time during the exposure show various kinds of trend with different time lag of the peak. The desorbed molecules including H2O, O2, CO, and CO2, have the time lag longer than those of H2 and hydrocarbon molecules. The longer beam dose exposed on the sample, the longer time lag of PSD peak trended. The phenomenon of exposure dose-dependent PSD relates to the surface condition of the exposed samples. A Secondary Ion Mass Spectroscopy (SIMS) system is built in the exposure chamber to assist the in-situ surface characterization. The correlation between the yield of both PSD and photoemission and the surface concentration during and after the exposure will be compared. The phenomenon of exposure dose-dependent PSD is described and compared.