In situ ultrahigh vacuum residual gas analyzer “calibration”

Knowing the residual gas spectrum is essential for many applications and research in ultrahigh vacuum (UHV). Residual gas analyzers (RGAs) are used for both qualitative and quantitative gas analyses, where the quadrupole mass analyzers are now the most popular. It was found that RGAs supplied by different manufacturers are not necessarily well calibrated for quantitative gas analysis. A procedure applied for in situ RGA “calibration” against a calibrated UHV total pressure gauge is described in this article. It was found that special attention should be paid to $H2$ calibration, as RGAs are usually much more sensitive to $H2$ than ionization gauges. The calibration coefficients are quite reproducible in Faraday cup mode, however, using the secondary electron multiplier requires frequent checks of the calibration coefficients. The coefficients obtained for the RGA allow the use of the RGA as an accurate device for gas spectrum analysis.