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Transpector CPM Operating Manual
4.6 Advice and Tips
4.6.1 Achieving Good Base Pressure in the CPM
The CPM vacuum manifold must be baked out after initial installation or whenever
the RGA sensor is exposed to air. After an eight hour bakeout and cool down, the
base pressure must be less than 5E-7 Torr at 40 eV, 200
A. If not, examine the
background mass spectrum to look for the largest peak. If the spectrum is
dominated by mass 18, continued bakeout is required to reduce water vapor.
4.6.2 Avoiding Trapped Gas when Sampling Valves are Closed
When V2 is closed, the sampled process pressure is trapped between V2 and O2.
This gas will pump out in a few minutes. It is best to keep V2 open until the process
pressure is evacuated. Then open V1 to scan the background spectrum of the
process vacuum system.
CAUTION
Close the sampling valves when finished with
measurements to avoid pressure bursts to the RGA if the
process is vented.
NOTE:
CPM will turn off emission and the electron multiplier and close all
sampling valves when a pressure burst occurs.
