GBS Elektronik MCA 166 - Manual (Page 55)

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• Check if the behavior changes if the pile up rejector is switched off. Check the signal from the
preamplifier. If the preamplifier signal rise time is slower than 500ns, then there is the danger that regular
pulses (especially the large ones) are misinterpreted as pile-up. Try to use another preamplifier or just
switch the pile-up rejector off.
• Similar effects can be seen if detector cables longer than 50m are used.
Dead time shown is very high although the countrate is low.
• This problem occurred with some older firmware versions and NaI detectors connected. Ignore it or
install newer firmware.
• There may be some detectors with excessive electronic noise. Try higher fast and slow threshold (You
have to edit a setup file with a text editor for this).
Too high background rate with BICRON detectors
• Set Fast Threshold to 600 (You have to edit a setup file with a text editor for this) for gain > 50 (Edit
setup file)
MCA battery does not charge correctly
• You have connected charger in a wrong order. Connect charger first to MCA and then charger to mains
HP 200 tells “main battery low” or “Hauptbatter. schwach”
• This is the battery of the HP and not the MCA battery! You can continue measuring, but should switch
the HP off most of the time to save its battery. Charge or change HP battery.
Everything should be okay, but the MCA gets no signals or just measures strange spectra
• wrong input polarity. Check input polarity, just toggle it for a test.
• The amplification is severely wrong set.
• wrong input mode. Check also ADC input mode
Strange error messages
• MCA opened recently, flat cables loose? Connect flat cable again .
Very bad resolution in a HPGe spectrum
• Detector worn out or defective. Change and regenerate detector.
• Problems with the high voltage module. Try another high voltage module.
Bad resolution in a HPGe spectrum or from a test generator, specially at high amplification factors
• Check electrical noise and EMC compatibility of surroundings. Some laptops and also some switch
mode power supply battery chargers may disturb. Remove all connections from the MCA to ground or to
mains voltages. Try a different computer / laptop / palmtop.
• Winding the cable to the detector / computer several times around a ferrite ring also may help
While opening a spectrum, the MCA program tells "Wrong data format" or "data format error"
• spectrum was created by another program or another program version Check results, do not mind
too high count rate
• Keep a bigger distance to radiation source. Try a less sensitive detector. Watch for your personal safety
• Check detector
Unexpected errors from the HP 200, “Memory allocation error”, total system crash of the HP200LX