Apparatus and method for detecting explosives

A neutron activation analyzer is described, consisting of a thermal neutron source and a high energy neutron source disposed to irradiate luggage, mail, and the like. An indium foil is then placed over the thermal neutron irradiated article for a period of time, and then counted with a geiger counter array. Silver foil may also be used for greater sensitivity. A panoramic picture of substances rich in nitrogen is provided. The article is then bombarded with high energy neutrons, transferred to an array of geiger counters, and a panoramic picture of substances rich in oxygen is provided. Appropriate circuitry can indicate on a CRT or other means articles with a high probability of containing explosives. (E.C.B.)