MCPD18 R104
4 Operation of the MCPD18
It is strongly advised to read the following sections completely before taking the detector to
operation and to strictly follow all given advices within it.
4.1 Getting Started
4.1.1
“Start Up” Procedure
Follow this procedure when taken the detector to operation the first time and after every venting.
Finish the complete cabling as described in chapter 3.
Be sure, that the vacuum pressure at the detector is remarkably below 1E-6mbar, otherwise the
microchannel plates might be damaged by a local discharging (in general: the lower the pressure, the
longer the lifetime of the MCPs).
Turn off all sources for electrons, ions, light or X-rays that might hit the detector.
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 the detector is in a
complete overload, even when they are not facing the detector directly. This will wear out
the MCPs very fast. Turn off ion pumps and ion gauges before turning on the high
voltage of the detector.
Turn on the high voltage carefully. The voltage increase should not exceed 400V per minute. A
schematic sketch on how to ramp the voltages during the “Start-Up” procedure is given Figure 2. The
starting operation voltage is specified in the specification sheet of the detector.
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).
High voltage sparks may seriously damage the detector anode or the MCPs. Observe the
chamber pressure carefully every time the high voltage is turned on. Switch off the high
voltage immediately in case of a temporary pressure rise by an order of magnitude or
more. This indicates high voltage sparking.
If sparking occurs, turn down the high voltage immediately and wait some time (up to 5
min.). Start the “Start-Up” procedure again with an increased ramp time. Turn off the
high voltage completely, stop the procedure and call SURFACE CONCEPT for further
assistance, if is it not possible to reach the operation voltage without sparking.
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