MAL-OPS-1026 v3 19
deviations beyond the mean should be used to dictate the alarm threshold. The
higher the k value, the lower the chance of a false alarm but the device becomes
increasingly insensitive to low counts from true sources. A k value of 5 is
recommended to obtain the best balance between false alarm rate and sensitivity.
If a high gamma alarm is triggered in
Search Mode with ID, the screen on the
right will be shown.
Using the right key to select “OK” will
dismiss the alarm. Using the left key to
select “Confirm” will take the device into
confirmation mode (Section 5.3).
Note that the exclamation point in the red
circle in the top left-hand corner will
remain in place until the threat is
removed, even if an alarm is dismissed.
5.2.3.2. High Neutron Alarm
As background levels of radiation vary as time progresses, so too must the
threshold above which an alarm would sound. A high neutron alarm is triggered
when the count rate registered by the neutron detector is assessed as being
significant (above threshold; the count rate is a result of background radiation plus
a radioactive source). The alarm threshold works by calculating sigma, the
standard deviation of how much the count rate fluctuates, and then multiplies it
by a value k, which is set by a user. The value k determines how many standard
deviations beyond the mean should be used to dictate the alarm threshold. The
higher the k value, the lower the chance of a false alarm but the device becomes
increasingly insensitive to low counts from true sources. A k value of 5 is
recommended to obtain the best balance between false alarm rate and sensitivity.
If a high neutron alarm is triggered in
Search Mode without ID, the screen on
the right will be shown.
Note that the exclamation point in the red
circle in the top left-hand corner will
remain in place until the threat is
removed, even if an alarm is dismissed.
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