IUVSTA 15th International Vacuum Congress (IVC-15), AVS 48th International Symposium (AVS-48), 11th International Conference on Solid Surfaces (ICSS-11)
    Vacuum Science & Technology Wednesday Sessions
       Session VST-WeM

Paper VST-WeM5
Simulation of Hydrogen Outgassing in a Fusion Device and a UHV Chamber by Recombination Limited Model

Wednesday, October 31, 2001, 9:40 am, Room 125

Session: Gas Sorption Phenomena I
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
Recently it has been asserted by Moore and Nemanic that hydrogen outgassing from stainless steel should be considered by recombination limited model, and they have proposed to use a thin-walled chamber of stainless steel. So we attempted to calculate the recombination rate of hydrogen at a metal surface by solving numerically one dimensional diffusion equation. The calculation were made for two cases: the redesorption rate of hydrogen implanted into the wall of a fusion device during hydrogen pulse discharge, and the hydrogen outgassing rate of a vacuum chamber during baking and in post-baking. For the second case, it was assumed that the initial hydrogen distribution in the wall before baking is uniform, hydrogen desorption occurs only on the vacuum side, and hydrogen permeation from the air side is negligible. As a result of numerical calculation, we will discuss the effect of thin wall on achieving a low outgassing rate in a short time by baking, the role of surface layer such as oxide layer, and so on.