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R. Dobrozemsky, J. Soltan-Mohammadi Khayat:
"Measurement of heavy gases and vapors by means of a conventional RGA";
Vacuum, 101 (2014), 451 - 456.

A conventional residual gas analyzer (RGA) has been utilized for the measurement of gaseous substances
of molecular weights far beyond the range of the instrument. The novel method, termed CPC ("crackproduct
calibration"), is based on the evaluation of just one or few selected crack products within the
range of the RGA. Calibration is achieved by guiding a quartz-microbalance-controlled molecular beam of
the substance under consideration through the RGA´s ion source and, at the same time, admitting a noble
gas with density de!ned by a Bayard-Alpert gauge (BAG) e thus anchoring the calibration of the RGA to
the readings of the more stable total pressure gauge. In this way, the RGA´s sensitivity can be characterized
and corrected with an accuracy that is essentially limited just by the reproducibility of the BAG
readings. By means of a twin-gas standard, even effects due to drift of the RGA´s !eld axis potential can
be corrected to a large extent. The basics of the method and the apparatus are described with special
attention to the measurement of silicone oil with a mean molecular weight above 100,000 g/mol, and to
the discussion of accuracy concerns.

Quadrupole RGA Crack-product analysis Calibration Transfer standard Silicone oil Heavy vapor