5 – 10
Transpector SPS Operating Manual
CAUTION
Do not operate the CDEM/FC detector at temperatures
above 150°C. Permanent damage may result.
CAUTION
Avoid output currents in excess of 1 x 10
-6
amps.
Either decrease the high voltage or decrease the
pressure.
Use the minimum CDEM/FC detector voltage required to obtain the necessary
peak amplitudes and/or signal-to-noise ratio. Operating at higher voltages than
necessary will result in premature aging of the EM. As the CDEM/FC detector
ages, the voltage needed to obtain a specific EM gain will increase.
Since EM performance depends on the condition of its interior surfaces, prevent
hydrocarbon or other contamination:
Make sure diffusion-pumped vacuum systems are properly trapped to reduce
oil back-streaming.
Make sure turbomolecular pumped systems are interlocked to eliminate
mechanical pump oil back-streaming through a nonspinning turbo pump.
EM gain reduction from these kinds of problems can range from 50% to more than
90%. The initial gain of the EM is generally high enough to accommodate some
degradation and yet still be usable. With repeated instances of contamination, the
EM will eventually require replacement.
CAUTION
In addition to hydrocarbon contamination, an EM can be
adversely affected by exposure to highly reactive
chemicals. Avoid any substance that will either cause the
deposition of a surface film on the EM or etch its surface.
Avoid high levels of reactive fluorides, such as tungsten
hexafluoride, hydrogen fluoride, and nitrogen trifluoride.
