Surface Characterization of the Vacuum Chambers by the Synchrotron Radiation Induced Outgas-Desorption Measurements

Gao-Yu Hsiung^1*, Chia-Mu Cheng¹

¹Instrumentation Development Division, National Synchrotron Radiation Research Center, Hsinchu, Taiwan

* Presenter:Gao-Yu Hsiung, email:hsiung@nsrrc.org.tw

The vacuum chambers for the synchrotron light sources, e.g. TLS or TPS, subjected the synchrotron radiation (SR) that induced significant outgas-desorption that caused the beam loss and the consequent high radiation and the beam-ion instabilities. The major outgas molecules contained the atoms of hydrogen, carbon, and oxygen, that desorbed from the surface of vacuum chambers after the complicated chemical reactions associate with the dissociation and the recombination induced by the synchrotron radiation, which is different from that of the thermal desorption of the vacuum baking. It has found the photon stimulated desorption (PSD) has generated the specific molecules that recombined the surface impurities, e.g. N or F atoms, from the surface oxide layers had not been observed from the baking. To inspect the SR induced the surface outgas-desorption, the experiments for measuring the PSD were performed on the 19B(PSD) Beamline of the TLS. The surface characterization and the behavior of the PSD outgas through the SR exposure will be presented.

Keywords: synchrotron radiation, photon stimulated desorption, accelerator, outgas, vacuum