ORTEC Micro-Detective-HX, Operation Manual

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5. MONITORING AND MEASURING WITH THE MICRO-DETECTIVE-HX
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5.2.1. Screen Features
!
The top section of the Detect screen displays the same
information as the Home screen, including the gamma
dose-rate meter, the gamma and neutron count-rate
meters, and the indicators for remaining memory card
space and battery time.
!
The center of the screen contains the Signal Index and
SNM Index. These “virtual strip charts” can indicate
nearby radioactivity even before IDs and alarms are
generated. Use them to help locate “hotspots” for Long
and Fixed Sampling. Both charts scroll from right to
left with time, providing short-term trend data based on
the HX’s analysis calculations. Keep in mind that these
are indirect indicators meant as quick visual tools, not
count-rate or dose-rate meters.
!
The Signal Index is based on the total gamma count rate
(including threat and innocent nuclides as well as gamma sources that are not in the library).
The peak height on this chart increases as you move the HX closer to a gamma source. When
an alarm is generated, the section of chart for that time interval is assigned the alarm color.
For simultaneous alarms, the chart displays the color of the highest-priority alarm.
!
The SNM Index is a function of the maximum confidence factor for all SNM indicators in
the library. These include U, Pu, Np, Am, and neutrons. For a single peak ID, the SNM index
is scaled as the ratio of net counts to net count error. The peak height on this chart increases
as you move closer to a threat material.
Figure 33 shows an identification and alarm for the threat nuclide Am-241. Note that the Signal
Index indicates a relatively weak radiation source(s); and the SNM Index reflects a high
probability that the source(s) includes Am-241.
The list of identifications in the real-time ID area can extend to
multiple pages. In such cases, the Detect page is entitled Detect 1
of [x], Detect 2 of [x], etc., where x is the total number of pages
of the report (see Fig. 34). Press or tap the S button to cycle
through the pages.
A summary report — the End Survey report — is displayed at the end of the measurement. It
shows all of the unique identifications made throughout, plus any new identifications that result
from analyzing the cumulative spectrum. The cumulative analysis is designed to check for
Fig. 33. Detect Screen During a
Survey.
Fig. 34. Two Pages of IDs
Available.