AVS 46th International Symposium
    Vacuum Technology Division Wednesday Sessions
       Session VT-WeM

Paper VT-WeM1
Affect on Pumping-Speed Measurements Due to Variations of Test Dome Design Based on Monte-Carlo Analysis

Wednesday, October 27, 1999, 8:20 am, Room 610

Session: Vacuum Pumping Systems
Presenter: S.B. Nesterov, Moscow Power Engineering Institute, Russia
Authors: S.B. Nesterov, Moscow Power Engineering Institute, Russia
Yu.K. Vassiliev, Moscow Power Engineering Institute, Russia
R.C. Longsworth, IGC-APD Cryogenics, Inc.
Correspondent: Click to Email
Test domes for measuring pumping speed are defined in AVS Standard 4.1, Pneurop Standard PN5ASRCC/5 and the last draft of the new AVS Standard for Cryopumps. These test domes are similar. They try to provide a measure of the speed of a pump as if it is mounted in the center of a large, flat plate in a large chamber. In this case, the flow distribution is diffuse while in the test dome the flow pattern has a stronger axial component. The location of the pressure gauge is intended to compensate for the different flow pattern. Certain parameters in the design of the test domes are not rigidly specified -- including the shape for the top of the dome, the diameter of the gas feed tube for the single-dome method or the orifice for the two-gauge method. A Monte-Carlo Analysis has been carried out to analyze the differences in speed which will then be measured for different configurations for the top of the test dome, different gas feed-tube diameters and different diameters of the hole in the aperature plate. Variations in the range of 2% to 3% are calcualted. In addition, a comparison of pumping speed for an APD Cryogenics Marathon 8 Cryopump mounted in a test dome vs. being mounted on a flat plate in a large chamber is presented in order to illustrate the potential affect of the cryopump geometry.