NAA Technical Information

Homeland Security needs explosive, contraband, and special nuclear materials detection schemes suitable for cargo containers and conveyers such as trucks, trains, airplanes, and ships at seaports, airports, and national borders.  These require some form of penetrating radiation, such as neutrons and gamma rays.  The large volumes implied require high intensities of radiation for adequate throughput.

Neutron activation analysis (NAA) is a powerful interrogation technique where incident, low energy neutrons interact with the stable isotopes in the volume under investigation, resulting in the emission of gamma rays with energies that are characteristic of the parent isotope.  This technique offers a quantitative isotopic analysis of the volume under interrogation, and is suitable for large volume interrogation as both the incident neutrons and the resultant gamma rays have sufficient penetrating capabilities.  Nuclear reactors are prolific sources of thermal neutrons.  However, for certain fixed locations and all mobile applications, accelerator-based neutron sources are required.  Obviously, the throughput of such detection schemes depends on the magnitude of the neutron flux – the larger the container, the larger the required neutron flux, which, for a linac-based neutron source, implies the need for cw operation.  The RFI linac structure has exceptional capabilities for CW operation.