SPECS 2D-CCD, User Manual

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Manual V2.docx | Status 10.12.2015 | Version 1
8. Click Store in PCU to save the settings.
9. Run a scan and check the performance of the channel with the new threshold
settings. See also section 4.3 and the Ferrum Spin detector manual for information
about the correct background level.
4.3 Noise
The easiest way to find the noise level from a CEM is to operate the detector without any
excitation source. A dark count rate of 2-4 counts per should be present in both channels of
the Ferrum detector.
Note
Switch off all sources of electrons, such as ion getter pumps and pressure gauges during the
measurement.
If the noise level is too high for one or more channels, perform the following:
•
Check that the preamplifier is working correctly, as described in section 4.1.
•
Check the grounding of the analyzer
If the checks above do not solve the problem, you can set a higher discriminator threshold
setting for the noisy channel(s)—see section 4.2. Set a value up to 10 mV.
For further information on testing and exchanging the CEMs, see the Ferrum Spin detector
manual.
4.4 Checking the voltages
The tables below show the voltages at the feedthroughs for lens mode LAD 400 V. If there
are any doubts about the correct operation of the instrument, you can check these with a
high precision voltmeter. For high voltage measurements, use a 1000:1 probe.
Danger—High Voltages Present!
Only qualified personnel using appropriate equipment should perform these measurements.
4.1.1 Detector settings
Table 3 shows the detector settings that you should apply. SPECS Juggler is a good
program to set these values.