Pulsed fast/thermal neutron analysis: a technique for explosives detection.

Explosives, narcotics and other contraband material contain various chemical elements, such as hydrogen, carbon, nitrogen and oxygen, etc. in quantities and ratios that differentiate them from each other and from other innocuous substances. Neutrons and gamma-rays have the ability to penetrate through various materials to large depths. They are able to interrogate, in a non-intrusive manner, volumes ranging from suitcases to Sea-Land containers. Pulsed fast/thermal neutron analysis (PFTNA) is a neutron-based technique which utilizes the (n,n'gamma), (n,pgamma), and (n,gamma) reactions to identify and quantify a large number of elements. The elements emit characteristic gamma-rays that are the 'fingerprints' of each isotope. This technique is being employed in a variety of applications: bulk coal analysis, contraband detection and detection of explosives.