Feasibility study of compact Neutron Resonance Transmission Analysis using a linac, a fusion-based neutron generator, and an isotopic source

Abstract

Various nuclear security applications such as fuel enrichment analysis and warhead verification seek to identify nuclear materials in a black box target. Neutron Resonance Transmission Analysis (NRTA) is a spectroscopic technique which uses resonant neutron absorption to identify isotopic compositions. Previous NRTA experiments have used expensive beam line facilities with kilometer-long accelerators. This work explores feasibility of compact NRTA configurations using a linear accelerator (linac), fusion-based neutron generator, and isotopic source. Monte Carlo simulations show that these configurations trade off between complexity and flux, which is related to measurement time. A 5.5 MeV linac may yield the highest epithermal (1-10 eV) neutron flux (10⁷ neutrons s⁻¹), but conversion of electrons to neutrons adds complexity, bulk, and expense. A deuterium-tritium (DT) fusion-based neutron generator produces a moderate neutron flux (10⁶ neutrons/s) and complexity relative to the linac and isotopic configurations. Isotopic NRTA may provide the simplest solution but limits flux to 10⁴ neutrons s⁻¹. Preliminary isotopic experiments indicate that limited source activity poses a challenge for overcoming gamma background. This thesis discusses feasibility of each proposed NRTA setup in various security applications.