30
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 15: Schematic plot of increasing the operation voltage to compensate
gain degradation over time as function of the extracted charge (all values are only
exemplary).
Typically, the final operation voltage at the end of the burn-in period will be close to the recommended
maximum operation voltage. An increase of the operation voltage above the recommended maximum
operation voltage is in principal possible and allowed, as long as there is no significant increase in the dark
count rate, bright spots at the detection area and/or appearance of high voltage sparking.
It is not unusual that the operation voltage must be increased several times especially in
the first year of operation.
Note
The operation voltage can be increased even above the recommended maximum
operation voltage. A safe and reliable operation will still be possible as long as there is
no increase in the dark count rate and/ or no appearance of high voltage sparking.
Note
DLD8080 R4.30 & R4.31 Manual | Surface Concept GmbH
