Outgassing rate of preconditioned vacuum systems after short exposure to the atmosphere: Outgassing rate measurements on Viton-A and copper
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When the sorption and desorption rates depend primarily on the diffusion of water vapor and atmospheric gases through the bulk of the sorbent (which may be an elastomer or plastic) and the process is reversible, then by an application of Fick`s law and Duhamel`s theorem equations can be derived for the outgassing rate as a function of time during subsequent pumpdowns in terms of the time of exposure to atmosphere with known relative humidity and the outgassing rate as a function of time during the initial conditioning cycle. Good agreement with the predictions of these equations has been obtained from measurements of repeated pumpdowns of a large-area sample of a Viton-A elastomer. However, similar experiments on copper plates showed relatively poor agreement with the theoretical equations indicating that the sorption--desorption process for water vapor in the oxide layer on metal surfaces may not be exactly reversible or that the process is not strictly controlled by diffusion. {copyright} {ital 1995} {ital American} {ital Vacuum} {ital Society}
- OSTI ID:
- 165046
- Journal Information:
- Journal of Vacuum Science and Technology, A, Vol. 13, Issue 2; Other Information: PBD: Mar 1995
- Country of Publication:
- United States
- Language:
- English
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