EXPLOSIVES DETECTION THROUGH FAST-NEUTRON TIME-OF-FLIGHT ATTENUATION MEASUREMENTS

Computer simulations have been used to devise an algorithm for detecti on of explosives in luggage which is based upon measured projected num ber densities of H, C, N, and O. Other elements are lumped together as projection X. Dependence on luggage-thickness is reduced by normalizi ng the projection for each element by the total. Normalization constra ins projections to a 4-dimensional space. Distributions of nonexplosiv e (N) and explosive (E) situations are generated by sorting results of simulations into bins in that 4-space. A detection matrix element, gi ven by the ratio E/(N + E) for each bin, is addressed by a measurement . For a realistic distribution of the numbers and types of luggage mat erials, the plastic explosive RDX, at 10% of suitcase thickness, can b e detected in a single pixel with 85% reliability and a false alarm ra te of 3%.