MCPD18 R104
Figure 5: Typical gain degradation of MCPs as function of the extracted output charge
After an initial burn-in period, in which the detector gain changes as a result of electron induced chemical
allocation together with degassing residual gas molecules from the inside of the channels, the MCP
performance is very stable over a large amount of extracted output charge. The MCP gain is also a function of
the detectors operation voltage. Therefore gain degradation can always be compensated by increasing the
detector voltage.
Detector delivery will still happen with the MCPs operating within the burn-in period, although the detector has
been operated for some longer time with highest count rates during the test phase, Therefore gain
degradation will be still significant in the first year of operation (or even longer, depending on applied count
rates) and becomes obvious by a decline of the detector performance. Therefore it will become necessary to
increase the operation voltage from time to time. Voltage increase should always be made in small steps
(typically 50 V). There is a recommended maximum operation voltage, to which the detector voltage can be
increased to compensate gain degradation over time. This voltage is given in the specification sheet of each
detector.
A typical behavior of the detector voltage increase over time to compensate gain degradation is given
schematically in Figure 6.
Figure 6: Schematic plot of increasing the operation voltage to compensate gain degradation over time
as function of the extracted charge (all values are only exemplary).
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