HotSpotter? Neutron/Gamma Detector Page: 8 of 10
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Figure 3, 232Th Spectrum
Figure 3 shows the spectrum obtained from a 232Th source with a 15 mm cube of CdWO4. Note the
logarithmic scale. The green represents the data from the HotSpotterTM; the white shows the region
over which the parabola was fit; the blue line shows the centroid as computed from the parameters
of the parabola.
All significant peaks were detected. The resolution of the CdWO4 is insufficient to separate the 911
keV 228Ac gamma ray from the 965 keV emission, and the 510 keV from the 583 keV 208T1
emission. The single escape peak from the 2614 gamma ray was not detected because its proximity
to the Compton edge distorts it sufficiently to make the quadratic fit insufficiently better than a
linear fit. An improvement in x2 of 60% was the criterion for accepting a peak.
STATUS
The HotSpotterTM prototype is essentially complete. Testing to date has demonstrated its ability to
detect and identify 235U (in a sample of uranium enriched to 400 235U), 137Cs, annihilation radiation,
and the emissions from 22Na. Work is in progress to decide on a reasonable list of isotopes to store
in the firmware's catalog.
Battery life has been found to be approximately 5 hours on a set of four 9V alkaline transistor radio
batteries, with the battery supplying the +5VDC regulator being the one to fail first. There is an
ongoing effort to find higher energy, lightweight batteries to substitute for the 9-volt batteries.
A viable alternative may be to use a set of AA batteries and DC-DC converters to generate -5 VDC
(for the analog amplifiers) and +12 VDC for the high voltage supply.
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Bell, Z. W. HotSpotter? Neutron/Gamma Detector, report, April 1, 2003; Oak Ridge, Tennessee. (https://digital.library.unt.edu/ark:/67531/metadc734451/m1/8/: accessed March 18, 2024), University of North Texas Libraries, UNT Digital Library, https://digital.library.unt.edu; crediting UNT Libraries Government Documents Department.