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    Vacuum Science & Technology Monday Sessions
       Session VST-MoA

Paper VST-MoA3
Effect on Capture Probability for a Commercial Cryopumpin Three Different Mounting Arrangements

Monday, October 29, 2001, 2:40 pm, Room 125

Session: Dry, Cryo & Other Forms of Pumping
Presenter: R.C. Longsworth, IGC-APD Cryogenics, Inc.
Authors: S.B. Nesterov, Moscow Power Engineering Institute, Russia
Y.K. Vassiliev, Moscow Power Engineering Institute, Russia
R.C. Longsworth, IGC-APD Cryogenics, Inc.
Correspondent: Click to Email
A recent Monte Carlo analysis by the authors of the capture probability of an APD Cryogenics M8 cryopump in a test dome per the AVS recommended practice showed it to be about 11 % higher than if tested in an idealized large standard dome (LSD). The same analysis showed that a pump with a uniformly porous inlet has the same capture probability in the test dome as the LSD. The analysis suggested that the geometry of the inlet louvers in the real cryopump and the different flow patterns in the two different domes results in the capture probability in the two different domes being different. Further studies have been done to analyze the flow patterns at the inlet to the M8 cryopump in a LSD and a test dome in order to obtain a more rigorous explanation of the difference. The analysis has been extended to the case where the M8 cryopump is mounted behind a typical gate valve to see if the test dome provides a more realistic standard than the present LSD.