Elemental imaging for contraband detection

Effective non-intrusive substance detection techniques require two basic qualities: ability to detect and recognize as many signatures of the relevant chemical elements as possible and to do it on as small as possible volume of the interrogated object. Some nuclear-based inspection techniques possess these unique qualities. These abilities open new possibilities in rapid and automated inspection of small and large objects, from airline passenger luggage to shipping containers, for explosives, illicit drugs, other hazardous material including nuclear and most dutiable items. Various imaging techniques and their signatures are reviewed. Techniques using emission tomography of induced gamma rays, such as thermal neutron analysis and fast neutron analysis as well as those using the time-of-flight technique to provide direct substance images, such as pulsed fast neutron analysis are described. Some images employing these techniques are shown and briefly discussed.