Large area imaging detector for long-range, passive detection of fissile material

Abstract

Abstract--Recent events highlight the increased risk of a terrorist attack using either a nuclear or a radiological weapon. One of the key needs to counter such a threat is long-range detection of nuclear material. Theoretically, gamma-ray emissions from such material should allow passive detection to distances greater than 100 m. However, detection at this range has long been thought impractical due to fluctuating levels of natural background radiation. These fluctuations are the major source of uncertainty in detection and mean that sensitivity cannot be increased simply by increasing detector size. Recent work has shown that this problem can be overcome through the use of imaging techniques. In this paper we describe the background problems, the advantages of imaging and the construction of a prototype, large-area (0.57 m 2 ) gamma-ray imager to detect nuclear materials at distances of ~100 m.

A Fieldable-Prototype, Large-Area, Gamma-Ray Imager for Orphan Source Search

“…These images are generated exactly as for the original proof-of-principle (POP) instrument [2]. In short, the linear location of the imager is determined by a Doppler fifth wheel mounted under the trailer.…”

Benefits of position-sensitive detectors for source detection with known background

“…The question of whether or not imaging information improves detection performance was addressed in [3] in the context of coded-aperture imaging systems. If the background intensity is known, reference [3] argued that imaging information does not improve the signal-to-noise ratio (SNR), therefore imaging information does not improve detection performance.…”

“…If the background intensity is known, reference [3] argued that imaging information does not improve the signal-to-noise ratio (SNR), therefore imaging information does not improve detection performance. However, if the background intensity is unknown, imaging may improve SNR [3] and thus detection performance by providing a means to separate the otherwise indistinguishable source and background photons. The analysis in this paper differs from that of [3] because we treat the problem from a detection task-based point of view.…”

“…However, if the background intensity is unknown, imaging may improve SNR [3] and thus detection performance by providing a means to separate the otherwise indistinguishable source and background photons. The analysis in this paper differs from that of [3] because we treat the problem from a detection task-based point of view. We analyze the task of source detection using the asymptotic performance of the GLRT applied to photon counting imaging and nonimaging detectors.…”

Active-mask coded-aperture imaging

“…T has been shown that gamma-ray imaging allows one to overcome local background variations when searching for orphan sources [1,2]. Two methods of gamma-ray imaging that work at the energies of interest for this application (~50 -3000 keV) are Compton and coded-aperture imaging.…”