Evaluation of neutron techniques for illicit substance detection

We are studying inspection systems based on the use of fast neutrons for detecting illicit substances such as explosives and drugs in luggage and cargo containers. Fast-neutron techniques can determine the quantities of light elements such as carbon, nitrogen, and oxygen in a volume element. Illicit substances containing these elements are characterized by distinctive elemental densities or density ratios. We discuss modeling and tomographic reconstruction studies for fast-neutron transmission spectroscopy.