Actions for Thermodesorption of gases from various vacuum materials [electronic resource].

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Thermodesorption of gases from various vacuum materials [electronic resource].

Published
Oak Ridge, Tenn. : Distributed by the Office of Scientific and Technical Information, U.S. Dept. of Energy, 1979.
Physical Description
Pages: 45 : digital, PDF file
Additional Creators
United States. Department of Energy. Office of Scientific and Technical Information
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Summary
A number of materials are commonly used as vacuum system walls. The desorption of gases from these materials may contribute significantly to the internal pressure of an unpumped device or to the gas load which a pump must handle in a dynamic system. This report describes the thermodesorption measurements made on a number of metals (molybdenum, nickel, Kovar alloy, copper, copper-2% beryllium alloy) and two insulators (molybdenum sealing glass ceramic and high alumina ceramic). All of the materials after typical cleaning and air exposure contain considerable gas. With a long 400/sup 0/ to 500/sup 0/ vacuum bake, however, all can be cleaned sufficiently so that they will not contribute appreciable gas to their surrounding when vacuum stored at room temperature for many years. Most materials display desorption kinetics which are first order (a single bond or trap energy must be overcome for desorption). It appears that the desorption of CO from Kovar is rate limited by carbon diffusion (D/sub 0/ approx. = .4 cm/sup 2//s and E/sub d/ approx. = 27,000 cal/mol). The desorption of hydrogen from glass ceramic also appears to be diffusion rate limited (D/sub 0/ approx. = 1 x 10/sup -3/ cm/sup 2//s and E/sub d/ approx. = 11,000 cal/mol). Carbon monoxide is the major gas desorbed from metals, except copper for which hydrogen is the major desorbing species. The insulators desorb hydrogen primarily.
Report Numbers
E 1.99:sand-78-1975
sand-78-1975
Subject(s)
Other Subject(s)
Note
Published through SciTech Connect.
06/01/1979.
"sand-78-1975"
Beavis, L.C.
Sandia Labs., Albuquerque, NM (USA)
Funding Information
AC04-76DP00789
View MARC record | catkey: 14462940