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CEM 4230 Detector Setup Manual
4.1 “Start Up“ Procedure for First Time Operation
4 Operation of the CEM
Note
Mistakes, which lead to wrong measurement results or damage the CEM can happen very
easily while taking the system into operation. Therefore it is strongly advised to read the
following sections completely beforehand and to strictly follow all advices given.
Due to gain degradation it will become necessary to increase the operating voltage from
time to time.
4.1.1 Basic Checks
We recommend this procedure when taking the system into operation the first time and after every
venting.
• Remove any cables/plugs from the feedthrough flange if connected.
• Use a multimeter to check the resistance between each of the three HV inputs “U-IN”, “U-OUT” and
“U-DET” on the CEM assembly and between any of the three inputs “U-IN”, “U-OUT”, U-DET” and ground.
The only measurable resistance should be between R(U-IN/U-OUT) of several 10 MOhm, of R(U-IN/U-
DET) of several 10 MOhm and of R(U-OUT/ R-DET) of 1 MOhm. All resistances towards ground should
be infinite (> 2 GOhm).
• Reconnect the cabling and finish it as described in chapter 3, if not already done.
• Turn on the power for all devices.
Ion gauges and ion pump are both sources for electrons and ions. Ion pumps can also be
a source for X-rays. They can produce so many particles/X-rays that a CEM is in complete
overload, even when not facing the particle source directly. This will wear out the CEM
very fast. Turn off ion pumps and ion gauges before turning on the high voltage.
• Switch on any HV supply.
• If possible, watch the vacuum pressure while increasing the high voltage; turn the voltages back, if an
unusual increase is observed in the pressure (indicator for high voltage sparking).
• Increase the voltage step wise up with around 400 V per minute to the operation voltage of the CEM. It
is given in the specification sheet of the detector.
