Stanford Research Systems RGA100, Руководство по эксплуатации и программированию

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Appendix D
SRS Residual Gas Analyzer
17
This dialog allows you to change parameters relating to the detector of the RGA. You may wish to
change the noise floor value (0 gives the slowest scan with the best signal to noise ratio, 7 is the fastest
scan with the poorest signal to noise ratio). For a complete discussion of detection limit vs. scan rate, see
page 4-8 of the RGA manual. Note that if your RGA is not equipped with an electron multiplier,
parameters pertaining to it should be unavailable.
WARNING!!
Changing only the gain or only the voltage parameters of the electron multiplier (EM) can ruin your
calibration. Changing these parameters
requires re-calibration of the electron multiplier. Otherwise, the
same partial pressure will produce different readings depending upon whether the multiplier is on or off.
You can do a manual calibration of your electron multiplier by following these steps:
Raise the high voltage setting of the EM
Set the Gain factor to 1
Run an analog scan in both faraday cup and EM detection modes, noting the partial pressure for
the same peak in both scans.
The ratio of these peaks is the gain under the new high voltage setting. Set the gain parameter to
this value.
For a complete discussion and instructions on the electron multiplier tuning procedure, see page 7-14 of
the RGA manual.
Close the Detector Setup Dialog by pressing ““Cancel””
Applying Power to the Filament
To turn the filament on, click the button labeled ““ON”” next to the label ““Filament””. After a few moments,
your menu should look something like the following figure.
WARNING!!
Your vacuum system should be at a pressure less than 1 x 10
-4
torr before turning on the filament.
Pressures greater than this threshold will quickly ruin the filament. For complete installation instructions
and vacuum safety measures, see Chapter 1 of the RGA manual.