Development of a Real-Time Fast Neutron Imaging Telescope (FNIT) for the Detection of SNM

We describe the development, testing and performance of a Fast Neutron Imaging Telescope (FNIT) with the capability of detecting and composing real-time images of a neutron source. A key signature unique to Special Nuclear Material (SNM) is the emission of fission neutrons. An efficient neutron detector that is sensitive to neutrons in the energy range of 1-10 MeV and with imaging capability represents a key tool for the interdiction of smuggling of clandestine amounts of SNM into the country. A small, modular, organic liquid scintillator detector - initially developed at the University of New Hampshire to study solar neutrons - has been tailored to locate fission neutron sources in homeland security applications. The principle of detection is based on multiple elastic neutron-proton scattering. By measuring the interaction locations and the recoil proton energies, we can determine the direction and energy spectrum of the primary neutron flux along with the location of the neutron source. Key parameters determined in the laboratory thus far have been an energy (trigger) threshold of 200 keV (proton equivalent) and a 5° (σ) angular resolution across a broad energy range. This paper outlines the most recent results on instrument development, the FNIT detector's response to SNM and real-time neutron imaging development.