Neutron resonance transmission analysis (NRTA) is a neutron interrogation technique applicable for the identification of nuclear materials with the capability for isotopic differentiation. It is suitable over a wide range of mid- to high-Z isotopes. Given the need for techniques for nuclear material identification in the realms of nuclear security, nonproliferation, and safeguards, NRTA presents a promising method for the detection and quantification of such materials. In the past, however, effective NRTA instruments relied on large beamline facilities that produce high neutron output, which presents logistical challenges when analyzing materials that may not be on-site.
This research builds on existing work to construct a portable NRTA device that would allow for the detection and characterization of nuclear material without the constraint presented by existing grounded large-scale facilities. This NRTA setup involves a D-T neutron generator surrounded by a moderator to generate epithermal neutrons, opposite a detector composed of GS20 lithium glass scintillators. Previous work has demonstrated the ability of this NRTA device to detect several millimeters of uranium shielded by several millimeters of lead with an 80% success rate over a half-hour period. This research works to improve the NRTA setup by limiting gamma background signals, through the optimization of the detector setup and employing B-coated straws with reduced gamma sensitivities, in replacement of lithium glass scintillators. Increasing the signal-to-noise ratio of measurements by addressing this gamma background not only improves the accuracy of such a device, but also presents potential applications for this technology to spent fuel and other high-gamma-producing targets.