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Proceedings Paper

Digital processing of signals arising from organic liquid scintillators for applications in the mixed-field assessment of nuclear threats
Author(s): M. D. Aspinall; M. J. Joyce; R. O. Mackin; Z. Jarrah; A. J. Peyton
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Paper Abstract

The nuclear aspect of the CBRN* threat is often divided amongst radiological substances posing no criticality risk, often referred to as 'dirty bomb' scenarios, and fissile threats. The latter have the theoretical potential for criticality excursion, resulting in elevated neutron fluxes in addition to the &ggr;-ray component that is common to dirty bombs. Even in isolation of the highly-unlikely criticality scenario, fissile substances often exhibit radiation fields comprising a significant neutron component which can require considerably different counterterrorism measures and clean-up methodologies. The contrast between these threats can indicate important differences in the relative sophistication of the perpetrators and their organizations. Consequently, the detection and discrimination of nuclear perils in terms of mixed-field content is an important assay in combating terrorist threats. In this paper we report on the design and implementation of a fast digitizer and embedded-processor for onthe- fly signal processing of events from organic liquid scintillators. A digital technique, known as Pulse Gradient Analysis (PGA), has been developed at Lancaster University for the digital discrimination of neutrons and &ggr; rays. PGA has been deployed on bespoke hardware and demonstrates remarkable improvement over analogue methods for the assay of mixed fields and the real-time discrimination of neutrons and &ggr; rays. In this regard the technology constitutes an attractive and affordable means for the discrimination of the radiation fields arising from fissile threats and those from dirty bombs. Data are presented demonstrating this capability with sealed radioactive sources.

Paper Details

Date Published: 6 October 2008
PDF: 10 pages
Proc. SPIE 7119, Optics and Photonics for Counterterrorism and Crime Fighting IV, 71190G (6 October 2008); doi: 10.1117/12.799814
Show Author Affiliations
M. D. Aspinall, Lancaster Univ. (United Kingdom)
M. J. Joyce, Lancaster Univ. (United Kingdom)
R. O. Mackin, Lancaster Univ. (United Kingdom)
Z. Jarrah, Hybrid Instruments Ltd. (United Kingdom)
A. J. Peyton, The Univ. of Manchester (United Kingdom)

Published in SPIE Proceedings Vol. 7119:
Optics and Photonics for Counterterrorism and Crime Fighting IV
Gari Owen, Editor(s)

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