AVS 46th International Symposium
    Vacuum Technology Division Tuesday Sessions
       Session VT-TuP

Paper VT-TuP8
True and Measured Outgassing Rates of a Vacuum Chamber of a Reversibly Adsorbed Phase

Tuesday, October 26, 1999, 5:30 pm, Room 4C

Session: Poster Session
Presenter: K. Akaishi, National Institute for Fusion Science, Japan
Authors: K. Akaishi, National Institute for Fusion Science, Japan
M. Nakasuga, Kyoto University, Japan
Y. Funato, Suzuka National College of Technology, Japan
Correspondent: Click to Email
We reported before that the outgassing rates measured in a 304 stainless steel chamber were dependent on pumping speed. So a pump down model based on the Temkin adsorption isotherm was constructed to explain theoretically the dependence of the measured outgassing rate on pumping speed. From the model an outgassing equation was derived, which describes the change of coverage of adsorbed molecules at the wall surface of the chamber with time. Two terms, true and measured outgassing rates of the vacuum chamber, appear in the equation, and it is shown that the true outgassing rate is proportional to the measred outgassing rate and the proportional constant reveals a reduction coefficient for the pumping speed of a vacuum pump. In this paper the magnitudes of the measured outgassing rates as a solution of the outgassing equation are estimated numerically as a function of pumping speed and compared to the measured outgassing data in experiment. A good agreement between theory and experiment for the measured outgassing rates is found.