Tracking of fissile material with neutron detector systems

In the context of current nuclear threats efficient means of locating and analyzing nuclear or radioactive material are extremely important. Portable systems for in-situ detection have surpassed lab systems in importance because of the necessity of investigating critical spots such as airports, train stations, stadiums, and facilities likely to draw the attention of terrorists or other criminals. A considerable number of portable gamma detection systems of high efficiency have been available for quite some time. In contrast, portable neutron detection devices with high efficiency for in-situ detection are still rare. Most recently, Ametek/ORTEC has provided the portable and battery-operated neutron detection system "Fission Meter" consisting of a detection unit with 30 3He tubes and a pocket PC as control unit. The system's output is meant to enable the user to distinguish between fissile and industrial material via detection of coincident neutrons. This way the location and characterization of nuclear or radioactive material in-situ is possible. The system was thoroughly tested at Fraunhofer-INT both at the lab and outdoors with neutron sources whose probability of emitting coincident neutrons varied considerably.