Stanford Research Systems RGA100, Operating Manual And Programming Reference

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6 Appendix A
SRS Residual Gas Analyzer
would have been without the cleaning. The mass spectrum provides a more accurate
evaluation of cleaning procedures than pump down time and base pressure. Just because
a system pumps down quickly does not guarantee that undesirable contaminants have
been eliminated.
The large dynamic range of the RGA also allows evaluations to be made more quickly.
After a vacuum system has been brought up to atmospheric pressure, it will require an
extended period to pump back down to its ultimate vacuum. If the vacuum system does
not quickly reach its ultimate vacuum, the next step is commonly a high temperature
bakeout. If the vacuum system has still not reached its ultimate vacuum, problems are
suspected and typically a leak tester would be attached to the system. With the RGA, the
user does not have to wait several hours for the water to pump down or perform a
bakeout before determining if a system is contaminated. The RGA can make
measurements as soon as the total pressure reaches 10
-5
mbar. The large dynamic range
will allow impurities to be seen at 10
-10
mbar or leak testing to be performed in the
presence of a this high total pressure. Thereby, the RGA allows a great reduction in turn-
around time after a vacuum system has been brought up to atmosphere.