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SM/EN-05
Air Cargo Inspection using Pulsed Fast Neutron Analysis
D.A. Strellis, J. Stevenson, and T. Gozani
Rapiscan Laboratories, Sunnyvale, California, United States of America
Corresponding Author: dstrellis@rapiscansystems.com
A powerful tool for air cargo inspection exists at the George Bush Intercontinental Airport in
Houston, Texas USA that utilizes the Pulsed Fast Neutron Analysis (PFNA) technology. Funded
by the Transportation Safety Administration under the United States Department of Homeland
Security, a system has been developed to detect explosives at the threat level in a wide range
of cargoes. The system utilizes a tandem Van de Graaff accelerator operating at 3.5 MHz that
produces pulses of deuterons with a FWHM of 1.5 ns. Neutrons of several nanosecond duration
are created through the d,D reaction at an energy of around 8 MeV at a deuteron beam intensity
of up to 140 micro-A. A neutron collimator near the deuteron gas target produces a neutron beam
spot 9-cm wide by variable (typical) 12-cm tall at the center of the container. This neutron beam
oscillates vertically by moving the collimator. Translational motion of the air cargo is provided
by a constant-velocity conveyor system. The inspection volume is surrounded by a large array
of 14-cm cube NaI detectors to collect the γ-rays from the neutron inelastic scattering reactions
occurring within the volume. Using the time–of–flight technique to determine the position in the
container in which the neutron inelastic scattering reactions occur, the data acquisition system
and the image reconstruction engine produce a three dimensional image of the cargo contents. The
images have a typical volume element granularity of 6.3 cm wide x 6.3 cm wide x 8 cm deep. The
latest signature measurements from the 4.44-MeV γ-ray from carbon, the 6.13-MeV γ-ray from
oxygen, and the 1.63-MeV, 2.31-MeV, and 5.55-MeV γ-rays from nitrogen of threat and non-threat
material, as well as images demonstrating the capabilities of this unique inspection tool, will be
presented. In addition, alternate applications; including, nuclear material detection, and other
uses for neutron beams of various energies will also be presented.
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