  Neutron Resonance Transmission Analysis (NRTA) uses resonant absorption of
neutrons to infer the absolute isotopic composition of a target object,
enabling applications in a broad range of fields such as archaeology, materials
analysis of nuclear fuel, and arms control treaty verification. In the past,
NRTA involved large user facilities and complex detector systems. However,
recent advances in the intensity of compact neutron sources have made compact
neutron imaging designs increasingly feasible. This work describes the Monte
Carlo (MC) based design of a compact epithermal NRTA radiographic instrument
which uses a moderated, compact deuterium-tritium (DT) neutron source and an
epithermal neutron detector. Such an instrument would have a wide range of
applications, and would be especially impactful for such scenarios as nuclear
inspection and arms control verification exercises, where system cost and
mobility may be of critical importance. The MC simulations presented in this
work demonstrate accurate time-of-flight (TOF) reconstructions for transmitted
neutron energies, capable of differentiating isotopic compositions of nuclear
material with high levels of accuracy. A new generation of miniaturized and
increasingly more intense neutron sources will allow this technique to achieve
measurements with greater precision and speed, with significant impact on a
variety of engineering and societal problems.
