Low energy fusion as a neutron source for security applications

Millions of containers cross national borders annually of which only a small fraction are inspected, typically with X-ray transmission imaging. X-rays provide a line integral of the density between source and detector meaning two materials with comparable density cannot be distinguished and high density materials can shield low density materials. When the requirement for human interpretation of X-ray images is combined with the poor material recognition the possibility of not identifying dangerous or illegal contraband becomes significant. Pulsed Fast Neutron Analysis (PFNA) is an alternative to X-ray imaging, which provides far more information and is less affected by shielding. Fast neutrons activate nuclei causing them to emit characteristic gamma rays (γs) unique to the element. Characteristic γs can be used to identify the chemical composition of material and so distinguish contraband from benign materials. By pulsing the neutron source time of flight information can be used to create a 3D image of the container, broken into voxels, allowing the precise location of any contraband to be provided to the operator. PFNA requires a rapidly pulsed, monochromatic neutron beam that may be provided by low energy fusion of protons and light isotopes. Simulations are being performed to identify a target isotope that will produce a neutron beam of the ideal energy and leave no long lived radioisotopes. In this paper we identify several low-energy interactions capable of producing neutrons suitable for security, and other possible applications. We also discuss the products produced in these reactions and suitable pulse structure.