Thermo Scientific SAM12, Manual

Page: 148 / 176

Calibration Procedure Issue: 1.0
10-4 SAM12 User Manual Thermo Fisher Scientific
The SAM12 will allow “calibration streams” to be set, which
will include a number nuclides and their associated percentage
in the mix. The SAM12 will take account of the respective
efficiency of the nuclide and the percentage, to evaluate the
overall efficiency of the SAM12 to the mix. Note that even
when the SAM is calibrated to a single nuclide, such as
137
Cs,
this is still treated as a single nuclide stream. Only those
nuclides to which the SAM12 has been calibrated, may be
included in the mix.
Calibration Selection (page 5-24) shows how to create the mix
for a new calibration stream.
It is not essential that the percentage of all the nuclides entered
adds up to 100 %. In this situation, the SAM12 will assume the
unidentified percentage is due to undetectable nuclides, such as
55
Fe, and adjust the overall percentage efficiency to the mix
appropriately.
Troubleshooting
CHECK IMMEDIATE AREA AROUND SAM12 FOR A
LOCAL SOURCE OR DIRECTIONAL BACKGROUND
FIELD “SHINE”.
The background operating voltage may be adjusted in steps of
25 V for a particular detector in order to increase or decrease
the background response to be more consistent with the other
detectors.
HOWEVER ANY ADJUSTMENT OF THE VOLTAGE
WILL INVALIDATE THE CCM AND NBR MODES,
WHICH MUST BE SET USING THE METHOD
DESCRIBED IN
Selection of Detector Operating Parameters
(page 9-3) .
If only one of the detectors is outside the required value,
change the relevant HV setting as described in the previous
section.
AGAIN, ANY ADJUSTMENT OF THE VOLTAGE WILL
INVALIDATE THE CCM AND NBR MODES, WHICH
MUST BE SET USING THE METHOD DESCRIBED IN
Selection of Detector Operating Parameters (page 9-3) .
Significant deviations form the expected efficiency indicate a
faulty detection assembly, and remedial action should be taken.
Calibration mixes
If Background Values Vary
by More Than 30%
If Nuclide Count-Rate
Outside Required Value