Preliminary results from a prototype neutron moderation imager

Neutron moderation land mine detection involves irradiating the ground with fast neutrons and subsequently detecting the thermalized neutrons which return. This technique has been studied since the 1950s, but only using non-imaging detectors. Without imaging, natural variations in moisture content, surface irregularities and sensor height variations produce sufficient false alarms to render the method impractical in all but the driest conditions. This paper describes research to design and build a prototype land mine detector based on neutron moderation imaging. The detector consists of a novel thermal neutron imaging system, a unique neutron source to uniformly irradiate the underlying ground, and hardware and software for image generation and enhancement. A proof-of-principle imager has been built, but with a very weak point source offset from the detector to roughly approximate a uniform source at the detector plane. Imagery of mine surrogates is presented. Realistic Monte Carlo simulations were used to estimate performance capability, including spatial resolution and detection times.