AVS 45th International Symposium
    Vacuum Technology Division Wednesday Sessions
       Session VT-WeA

Paper VT-WeA9
Characterization of Aluminum Materials Focusing Electron Stimulated Gas Desorption and Its Surface Analysis in Surface Treatment Techniques

Wednesday, November 4, 1998, 4:40 pm, Room 329

Session: Vacuum Systems and Components
Presenter: M. Nishiwaki, KEK, Japan
Authors: M. Nishiwaki, KEK, Japan
S. Kato, KEK, Japan
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In a hot vacuum environment such as a particle accelerator, gas desorption from a vacuum surface during the operation seriously affects the stability, the quality and the lifetime of the electron or ion beam. In order to adopt vacuum materials and surface treatment techniques to hot vacuum, reported data of thermal outgassing from vacuum surface do not always give established indication for outgassing due to particle irradiation. Therefore it is very important to evaluate gas desorption of the materials and the treatment techniques using energetic particle bombardment. We focused on measurement of electron stimulated gas desorption from aluminum materials mainly and its surface analysis in this study. Four different surface treatment techniques for aluminum materials were carried out to make comparison, that is, machining with oil lubricant and subsequent degreasing (OL), machining with a liquid jet of ethyl alcohol (EL), machining in a gas mixture of argon and oxygen (EX) and machining with corona discharges in the same gas mixture (EXP). In order to measure electron stimulated desorption rates from those surfaces quantitatively, a throughput method was used with a pressure calibrated RGA. The base pressure of the sample chamber was in an order of 10@super -7@ Pa. Electrons from an e-gun were irradiated against the samples at a typical condition of a kinetic energy of 1.5 keV, a current density of 10@super -3@ A/cm@super 2@ at a normal incident and a sample temperature of 27 ° C. Surface characterization of those samples was also done by use of Auger electron spectroscopy with sputter etching. This gives information about depth profiles of atomic compositions in an altered surface layer due to the treatment discussing the relation between the electron stimulated desorption rates and the surface atomic compositions.