Fast-neutron transmission spectroscopy for illicit substance detection

Fast-Neutron Transmission Spectroscopy (FNTS) is being investigated for detection of explosives in luggage or other small containers. This technique uses an accelerator to generate nanosecond-pulsed deuteron beams that strike a target, producing a white source of neutrons. Elemental distributions along projections through the interrogated object are obtained by analyzing neutron transmission data. Tomographic reconstruction is used to determine the spatial variations of individual elemental densities are combined in a detection algorithm that indicates the presence or absence of explosives. The elemental unfolding and tomographic reconstruction algorithms have been validated by application to experimental data. System studies have been performed to study the operational characteristics and limitations of a FNTS system, and to determine the system's sensitivity to several important parameters such as flight path length and the position of the interrogated object.