SAIC Exploranium – GR-135 System Manual page: 38
c) ADC – denotes the number of channels in the spectrum – system is currently hard wired at 1024
channels = 3keV/channel
d) AUDIO – selections are
ON, OFF
This sets a mode so that at the end of the data sample the audio will beep to remind users that the
sample is complete. The OFF selection sets no beep.
e) GAIN CORR – selections are
ON, OFF
This enables the automatic correction of detector drift as a function of temperature. Normally this is
ON as this feature is mandatory for proper system operation. However under special conditions the
user may wish to disable this correction so an OFF capability is permitted
10.3.3 CZT
This sets system parameters for the optional CZT detector. Parameters are the same as the NaI
detector selections. See section 9.3.2 for a detailed explanation of each selection
a) MEAS TIME – sets the detector sample rate – selections are 60, 120,
300, 500, 1000, 2000secs.
The CZT detector is very small and relatively inefficient so much longer sample times are required for
correct operation
b) MEAS MODE – usually set at
CLOCK
c) ADC – fixed at
1024 channels
d) AUDIO – usually set
ON
e) CZT OFFSET – set by the factory – see system CALIBRATION SHEET for the correct value
10.3.4 NEUTRON
This sets the parameters for the Neutron detector -
a) N SUMMING – Selects the data averaging. Selections are OFF, 3P,
5P, 10P - this parameter only
applies to the SEARCH mode data analysis. The default selection “5P” sets a 5 sample moving SUM
for the data. Users should note that this is NOT a moving average but a moving SUM. The reason
for this is to improve effective sensitivity. Since the Neutron detector is quite small in area, during
operation occasionally for statistical reasons the sample counts may be zero. If an average is used
then this “pulls” the average down. Since we are using Integer math here it is impossible to use
non-whole numbers as a threshold to compensate. So using the SUM method means that integer
values can readily be used without limiting system performance. The only disadvantage to this
method is the N SUMMING/ ALARM LEVEL and SAMPLE TIME are interactive so users should consider
all these parameters before selecting the final set of parameters. It is recommended that the
DEFAULT values be used for best performance in the SEARCH mode.
b) ALARM LEVEL – Sets the detector alarm level in COUNTS. Selections are OFF, 1, 2,
3, 4, 5, 6, 7,
8, 9, 10, 20, 50, 100 counts - this parameter only applies to the SEARCH mode data analysis. Since
the detector has a very low Gamma interference the 3 level is recommended for good sensitivity.
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