Development of a portable directional thermal neutron detection system for nuclear monitoring

Abstract A directional thermal neutron detector has been developed that is capable of locating sources of thermal neutron emissions. The detector is based on large area silicon detectors in a modular design that is configured to take advantage of the non-isotropic angular response of the detectors to determine the direction of the radiation source. The detector module consists of a thin gadolinium converter foil sandwiched between two planar silicon detectors coupled to an eight channel hybrid shaping amplifier and discriminator. A microcontroller unit processes the data in real time and displays neutron and gamma count rates and directional information. Detector modeling and tradeoff analyses were conducted to specify design criteria. Radiation transport methods were used to compute detector efficiency, front-to-back detector response and measurements were made to substantiate the detector modeling. Tests were conducted with the array to evaluate directional sensitivity under various measurement conditions.