AVS 52nd International Symposium
    Vacuum Technology Tuesday Sessions
       Session VT-TuM

Paper VT-TuM7
Residual Gas Analyzers as Total Pressure Gauges*

Tuesday, November 1, 2005, 10:20 am, Room 200

Session: Total and Partial Pressure Gauging
Presenter: M. Maskell, Old Dominion University
Authors: M. Maskell, Old Dominion University
P. Adderley, Jefferson Lab
G.A. Brucker, Stanford Research Systems
C. Day, Forschungszentrum, Karlsruhe
G.R. Myneni, Jefferson Lab
Correspondent: Click to Email
Residual Gas Analyzers (RGAs) provide many benefits over other types of gauges that measure total pressure only. RGAs give information about the specific composition of the residual gas in a vacuum system, and can be used for leak detection and diagnosis of other problems in a vacuum system. When the partial pressure capabilities of an RGA are needed, it is economically advantageous to be able to use the RGA as the systemâ?Ts total pressure gauge, rather than installing a total pressure gauge in addition to the RGA. The problem with using RGAs as total pressure gauges is that their sensitivity is affected by the mass of the gas they are detecting. These effects may be small for individual species of gas, but when the errors are added together in calculating the total pressure from the sum of the partial pressures, the total pressure measurement can become much less accurate than for gauges that measure total pressure only. This study is intended to find correction factors that can be applied to different gas species to make the RGA as accurate as any total pressure gauge. In this study, we use four Stanford Research Systems 100 AMU RGAs, an Ionivac IM-520 extractor gauge, an Ulvac AxTRAN gauge, and an MKS SRG SH-700 Spinning Rotor Gauge (SRG). First the SRG transfer standard is used to calibrate the extractor and AxTRAN gauges, by introducing various gases into the system, by direct comparison method. Then the RGA sensitivities for individual gas species are determined by comparing the partial pressure reading of the RGA with the extractor and AxTRAN gauge readings. Finally, a preselected gas mixture is introduced into the system, and the change in pressure reading on the extractor and AxTRAN are compared to the total pressure of the RGA with appropriate corrections to the various peaks of the RGA output. *This work was supported by U.S. Department of Energy Contract No. DE-AC05-84ER40150 and KATRIN International Collaboration at FZK in Germany.