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       Session VST-WeA

Paper VST-WeA7
Effect of Readsorption in a Dynamic Vacuum System

Wednesday, October 31, 2001, 4:00 pm, Room 125

Session: Gas Sorption Phenomena II
Presenter: P. Repa, Charles University, Czech Republic
Authors: P. Repa, Charles University, Czech Republic
L. Peksa, Charles University, Czech Republic
T. Gronych, Charles University, Czech Republic
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Theoretical analyses of the pressure variations in vacuum chambers considering desorption and adsorption indicate that the time-pressure curves shall be modified by readsorption of the gases penetrating through or releasing from the walls.@footnote 1@. Nevertheless, no effect of readsorption was observed at some recent experiments@footnote 2-5@ which were curried out in sealed-off vacuum systems and the phenomenon has not been explained entirely yet. An aim of this work was to study an effect of readsorption on pressure variations in a dynamic vacuum system. Doses of several gases (H@sub 2@, CO, and H@sub2@O) were introduced into a uhv chamber of the apparatus that was simultaneously pumped. For the measurements, an apparatus was used that consist of a uhv chamber of volume 0,025 m@super3@ pumped by a uhv pump and a gas handling system enabling to vary a throughput of an introduced gas precipitously. The pumping speed of the pump could be set at values up to 0.1 m@super3@/s by a reduction valve. In the course of the measurements, the total and partial pressure vs. time curves were recorded at several selected pumping speeds. An analysis of the response of the pressure in the chamber to sudden variation of the throughput of the introduced gas implied that the influence of readsorption on the pressure behaviour was immeasurable small not only in the sealed-off but also in the dynamic vacuum systems as well. @FootnoteText@@footnote 1@Redhead P. A., J. Vac. Sci. Technol. A14, 2599 (1996). @footnote 2@Berman A. and Fremerey J. K. J., Vac. Sci. Tecnol., A5, 2436 (1987) @footnote 3@Bennett K. J. and Elsey R. J., Vacuum 44, 159 (1993) @footnote 4@Jousten K., Vacuum 47, 325 (1996). @footnote 5@Takeuchi K. at all, J. Vac. Soc. Japan 35 837 (1993) .