AVS 50th International Symposium
    Vacuum Technology Thursday Sessions
       Session VT+MS-ThM

Paper VT+MS-ThM4
A Portable Reference Gas for InSitu Calibration of Residual Gas Analyzers

Thursday, November 6, 2003, 9:20 am, Room 323

Session: Reproducibility, Precision, and Accuracy of Vacuum and Process Measurements
Presenter: R.E. Ellefson, INFICON, Inc.
Authors: R.E. Ellefson, INFICON, Inc.
W.P. Schubert, INFICON, Inc.
L.C. Frees, INFICON, Inc.
Correspondent: Click to Email
A new design for a portable source of reference gas with a fixed flow rate has been developed for producing a repeatable pressure in the ion source of a residual gas analyzer (RGA). The fixed flow rate of gas flowing through the fixed conductance of the isolation valve located between the process vacuum system and the RGA produces a repeatable pressure at the ion source of the RGA. The flow rate of 1x10@super -4@ Torr-l/s of Ar (and selected impurities) through the typical conductance of 10 l/s produces a reference pressure of 1x10@super -5@ Torr in the ion source. The ability to produce a repeatable pressure at the ion source on demand enables calibration of the mass scale, electron multiplier (EM) gain and measurement of absolute sensitivity. Data on sensitivity versus time is shown as an example of a quality assurance method for determining the stability of operation of an RGA and to determine when sensitivity or EM gain adjustment is necessary. The same reference gas source can be used for the calibration of closed ion source RGAs that have their own pumping system. The mechanical design minimizes the pressure burst at turn on and accomplishes viscous flow of the gas mixture. Data is presented on consumption rate, expected lifetime, shipping exemptions, temperature dependence of flow rate and species fractionation over lifetime. Methods for species abundance calibration in the RGA are also presented.