Long range neutron-gamma point source detection and imaging using unique rotating detector

We propose a new radiation detection technology that offers high sensitivity to both gamma rays and neutrons, and can be applied, cost effectively, to survey monitoring. The detector consists of a close-packed array of many small thin-walled copper straws, each 1 m in length, and lined with a very thin (1 mu m) coating of enriched boron carbide ((B4C)-B-10). Gammas are converted in Cu, while thermal neutrons are converted in B-10. The detector design draws upon low-cost technology developed by the high energy physics community for large particle detectors such as ATLAS, currently being commissioned at CERN. The feasibility of the detection technology has been demonstrated previously [1], [2]. The current work presents a unique application of the straw detectors, whereby a rotating panel is used to significantly improve performance. The proposed concept is based on the characteristic signature of a point source, that differentiates it from background noise. We present and evaluate an algorithm for detecting the presence of a source and estimating its net count, direction, and the background rate. Simulation results show that the proposed technique can detect in about 20 minutes time and in an area 100 m in diameter, a 1 mCi gamma ray source, with 90% sensitivity and false alarm probability of 0.1/hour. At 30 min time, 270 g of neutron-emitting Pu-240 can be detected within a circular area 100 m in diameter, assuming 20% of neutrons thermalize near the source.