<title>Transport simulation and image reconstruction for fast-neutron detection of explosives and narcotics</title>

Abstract

R ( 1 1 -7. : _I Argonne, Illinois 60439 USA Ad::.,$ 0 j .Fast-neutron inspection techniques show considerable promise for explosive and narcotics detection. A key advantage of using fast neutrons is their sensitivity to low-2 elements (carbon, nitrogen, and oxygen), which are the primary constituents of these materials. We are currently investigating two interrogation methods in detail Fast-Neutron Transmission Spectroscopy (FNTS) and Pulsed Fast-Neutron Analysis (PFNA). FNTS is being studied for explosives and narcotics detection in luggage and small containers for which the transmission ratio is greater than about 0.01. The Monte-Carlo radiation transport code MCNP is being used to simulate neutron transmission through a series of phantoms for a few (3-5) projection angles and modest (2 cm) resolution. Areal densities along projection rays are unfolded from the transmission data. Elemental abundances are obtained for individual voxels by tomographic reconstruction, and these reconstructed elemental images are combined to provide indications of the presence or absence of explosives or narcotics. PFNA techniques are being investigated for detection of narcotics in cargo containers because of the good penetration of the fast neutrons and the low attenuation of the resulting high-energy gamma-ray signatures. Analytic models and Monte-Carlo simulations are being used to explore the range of capabilities of PFNA techniques and to provide insight into systems engineering issues. Results of studies from both FNTS and PFNA techniques are presented.

Evaluation of few-view reconstruction parameters for illicit substance detection using fast-neutron transmission spectroscopy

“…In these studies we will use the exact projection data as calculated from the actual elemental densities in the slice being interrogated. Previous work using Monte Carlo simulations of the transmission for relatively simple phantoms [2,6] has shown good agreement between calculated and exact projection densities.…”

Evaluation of few-view reconstruction parameters for illicit substance detection using fast-neutron transmission spectroscopy

“…Previous work using Monte Carlo simulations of the transmission for relatively simple phantoms [2,6] has shown good agreement between calculated and exact projection densities.…”