Results of tests for explosives in luggage from fast-neutron time-of-flight transmission measurements

Jack C. Overley; Michael S. Chmelik; R. J. Rasmussen; G. E. Sieger; R. M. S. Schofield; Harlan W. Lefevre

doi:10.1117/12.267904

27 February 1997 Results of tests for explosives in luggage from fast-neutron time-of-flight transmission measurements

Jack C. Overley, Michael S. Chmelik, R. J. Rasmussen, G. E. Sieger, R. M. S. Schofield, Harlan W. Lefevre

Proceedings Volume 2867, International Conference Neutrons in Research and Industry; (1997) https://doi.org/10.1117/12.267904
Event: Fifth International Conference on Applications of Nuclear Techniques: Neutrons in Research and Industry, 1996, Crete, Greece

Abstract

Energy-dependent neutron attenuations measured by time-of- flight techniques are fitted with measured cross sections to determine projected number densities of H, C, N, and O in each 3 by 3-cm² pixel of a suitcase. Attenuations due to other elements are lumped together as element X. Number densities are normalize by the total to reduce effects of variable thickness. Normalized number densities are constrained to lie in a 4D space. That space is finely binned. A fifth dimension contains six bins of N + O density, as deduced from average suitcase thickness and measured projected number densities. Each bin is labeled with the probability of encountering an explosive, as determined from distributions of elements from simulated explosive and nonexplosive situations. Probabilities for individual pixels are combined to produce an overall probability of an explosive suitcase. About 130 measurements involving 50 suitcases have been made. For about half of those measurements, an explosive was placed in the suitcase. Ten different plastic explosives were used in varying amounts and configurations. When suitcases are ordered by explosive probability, and a threshold is set to minimize errors, the false alarm rate is about 2 percent and the explosive detection rate is about 88 percent. Potential improvements are discussed.

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Jack C. Overley, Michael S. Chmelik, R. J. Rasmussen, G. E. Sieger, R. M. S. Schofield, and Harlan W. Lefevre "Results of tests for explosives in luggage from fast-neutron time-of-flight transmission measurements", Proc. SPIE 2867, International Conference Neutrons in Research and Industry, (27 February 1997); https://doi.org/10.1117/12.267904

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