Chapter 5 Parameters Definition
114
Line Items
Detector Section Alarm sets the role of individual detector sections (singles) during
monitoring. The choices are identical to those for sum zone alarm.
If using the “Yes” choice causes a large increase in count time review the zone
information on the F6 – Monitor Zone Status screen, determine which zones need the
most time. Check the calibration of these detectors. Each single detector section in a
sum zone should have a similar efficiency.
Sum Zone Pair Alarm / Sum Zone Triple Alarm:
Sum Zone Quad Alarm / Sum Zone All Alarm:
These items provide a convenient means to quickly enter the Zone Alarm setting (see
F2 – (Zone) Settings screen) for all zones of the same type (singles, intra pairs, inter
pairs, etc.). These settings address the need to detect a source distributed over one,
two, three, or four adjacent detector sections, or all detectors together.
The choices for zone handling are “Yes”, “Individual”, “Yes (but don’t use for count
time)” and “No”. Selecting “No” disables zone checking; “Yes (but don’t use for
count time)” was previously called “Check”. It performs the contamination check on
the zones, but does not use the zones to determine the system count time; “Yes”
performs the contamination check on the zones and also considers the zones when
determining the count time.
Allow Individual Sigma Factors: The K Alpha, K Beta and K Delta sigma factors
(discussed below) are usually set globally on this screen for all detection zones.
These factors may be set either globally (default) or individually for each zone. If set
to “Yes”, the remaining items on this screen are hidden and the sigma factors are set
instead on the F2 – (Zone) Settings screen for each zone individually.
Bkg False Alarm (K Alpha)/Extend Alarm Confidence (K Beta 1)/Alarm
Confidence (K Beta 2)):
Note: These fields are hidden if “Bayesian” Methodology was selected from the
F10 – Methodology Configuration Menu in the Factory Setup Menu.
K Alpha and K Beta are statistical terms for multipliers of the error value or sigma
value in the count rate measurement caused by the random nature of radioactive
decay events. The K Alpha term relates to the false alarm rate due to a fluctuating
background while the K Beta term relates to the confidence that the system will alarm
for a true “contaminated” condition.
Use the CTRL+F10 - Factory Setup, F10 - Methodology Configuration - K
Interpretation setting to pick “one-tailed” or “two-tailed” integration when
computing values to right of Bkg False Alarm (K Alpha), Extend Confidence (K Beta
1), Alarm Confidence (K Beta 2).
K Alpha is used to calculate Equation 25 on page 286, K Beta 1 is used to calculate
CTP (Equation 27 on page 287) and K Beta 2 is used to calculate ATP (Equation 28
on page 287).
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