CR-39 detectors were exposed to DT neutrons generated by a Thermo Fisher model A290 neutron generator. Afterwards,
the etched tracks were examined both optically and by scanning electron microscopy (SEM). The purpose of the analysis
was to compare the two techniques and to determine whether additional information on track geometry could be obtained
by SEM analysis. The use of these techniques to examine triple tracks, diagnostic of ≥9.6 MeV neutrons, observed in
CR-39 used in Pd/D co-deposition experiments will also be discussed.
The multiple coincidence technique uses 14.1 MeV neutrons to produce (n, multiple-γ) coincidences to detect fissile and
fissionable materials. Measurements of n-γ-γ coincidences with targets of depleted uranium (DU), W, and Pb, show that
the counting rate for the DU is substantially above that for the non-fissionables. Also, the data involving prompt
neutrons and delayed gammas in the DU time spectra provide a signature for fissionables that is distinct from that of
non-fissionables.
Associated particle imaging (API) is a technique that employs a small deuterium accelerator to accelerate deuterons into a tritium-impregnated target, producing coincident neutrons and alpha particles that travel in opposite directions. By detecting the arrival of an alpha particle on a phosphor, and its position in two dimensions, the time and direction of the neutron emission id determined. Neutrons that interact with material in their paths produce a gamma ray whose energy is characteristic of that material. From the arrival time and energy of these gammas, the elemental composition of an object can be deduced as a function of position. We have built a portable API system and conducted field tests. In these tests, we have identified a quantity of fertilizer 'hidden' in a closed vehicle and the contents of some common military munition casings.
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