Surface Concept Delayline DLD 8080, Руководство пользователя

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DLD8080 R4.30 & R4.31 Manual
It can be sufficient to estimate the correct operation voltage by monitoring the detector results, when
increasing the voltage to compensate the gain degradation. The exact operation voltage can always be
determined by measuring a so called MCP curve. The MCP curve plots the detected count rate as a function
of the operation voltage. Do as follows to measure an MCP curve:
• Start the detector operation with an homogeneous illumination (as good as possible).
• Open the rate meter of the GUI software to monitor the count rate output of the detector (see GUI
software manual for details).
• Decrease the operation voltage until the count rate of the detector is reduced to zero.
• Increase the operation voltage in steps of 50 V until far above the last operation voltage (please respect
the recommended maximum operation voltage) or until the detector shows significant artifacts.
Measure the count rate for each voltage step.
• Plot the measured count rate as a function of the operation voltage. This is the MCP curve. It should
show a change in the slope of the rising curve, which indicates the beginning of the area of operation.
• The new value for the operation voltage should be a bit above the position of the change in the slope.
Figure 16
shows an example of a MCP curve with the specified operation voltage. The MCP curve for
specifying the starting operation voltage for a detector can always be found in the specification sheet.
Figure 16: Example of MCP curve.
The life time of MCPs can be very large, due to the high stability of the operation performance over a
large amount of extracted output charges after the burn-in period. The main reason for an often much
shorter operation time of the MCPs is an inhomogeneous irradiation of the MCPs. This is connected to a
locally (strong) different gain degradation, which results in an inhomogeneous detector response. Locally
different gains can still be compensated by increasing the operation voltage, but very often the increasing
voltage step must be much larger to reach again a homogeneous detector response.
Gain degradation also depends strongly on the environment in which the MCPs are being operated. Care
should be taken to prevent exposure to high concentrations of hydrocarbons and halogens. Also prevent
MCP operation at higher temperatures (> 50°C, e.g. respect an appropriate cooling phase after bake out).
DLD8080 R4.30 & R4.31 Manual | Surface Concept GmbH