switch the Device Adjust screens by clicking on the Stab or Gain button,
then back to the Filter Device Adjust screen.
3.
Unsuccessful BDC and Error Messages
If the Auto BDC operation fails to complete after initiation, the BDC BUSY
LED will turn off and the message “General SAD error” will be posted in the
error dialog box. Click on the Ok button to clear the message.
The BDC operation could have failed for one of the following reasons:
a.
BDC Time Out Error
– The Auto BDC has failed to complete within
a maximum time of five minutes. This may result if the detec-
tor/preamp signal is not connected or the incoming count rate (ICR) is
below 1 kHz. Additional causes may be excessive noise or abnormal
variations of the Trapezoid baseline. This could result from excessive
detector microphonics, high voltage arching in the detector or preamp,
secondary preamp signal time constants or a damaged detector. For
this case, the Flat Top may be set manually; select FLAT TOP under
the Filter parameter group.
b.
Incoming Count Rate Too High
– The incoming count rate (ICR)
exceeds 20 kHz. The Auto BDC will not operate properly if the ICR
exceeds 20 kHz. For this condition, the error message will be posted
very quickly, long before the time out occurs.
Spectroscopy Operation
Please refer to the Model 556/556A AIM and MCA Software User’s Manuals for spe-
cific operating instructions for your MCA.
Place a low activity
60
Co source on the detector. Set the MCA to COLLECT or
ACQUIRE. For the 9660 setup performed in “Spectroscopy System Setup” on page
34, the 1332 keV
60
Co peak should collect in channel 6500 to 7200 for a detector
preamp gain of 500 mV/MeV and 8192 memory or spectrum size.
Adjust the 9660’s gain to position the
60
Co peaks to the desired MCA spectral loca-
tion. The Super Fine Gain (SFG) control provides 100 times more resolution than the
Fine Gain. Use the SFG when matching the gains of several detectors or when estab-
lishing a specific gain calibration (energy per channel).
Chapter 6 - Setup and Operation
46
Model 9660-9660A ICB Digital Signal Processor