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Proceedings Paper

Fast time correlation detection in associated particle spectrometry of spontaneous fission neutrons and cosmic-ray backgrounds
Author(s): Leon Forman; Istvan Dioszegi; Peter E. Vanier
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Paper Abstract

We have investigated neutron spectrometry using fast gamma-ray detectors (BaF2) in coincidence with a gamma/neutron detector (plastic scintillator). Neutron spectra of spontaneous fission sources are determined by time-of-flight between correlated gamma and neutron detections using the associated particle (AP) technique. When the source is within a ~1 meter zone of detector separation, the correlated neutron detection efficiency is high because of the multiplicity of gamma-rays (10 gammas/fission in 252Cf) and neutrons (3.6 neutrons/fission). Cosmic-ray produced neutron detection efficiency is quite low in an AP measurement using a <50ns coincidence window because time-of-flight of most events is long from its creation within the 120 meters e-folding neutron range of air. We found that the AP signal to background ratio was dominated by uncorrelated coincidences and propose a triple coincidence system (1 neutron and 2 gamma-ray detectors) to improve performance. The gamma/gamma-ray coincidence time distribution is related to the target's production history where fast neutron multiplication may be a dominant physical process. MCNPX calculations suggest that the gamma-ray time history of Depleted Uranium (DU) and Highly Enriched Uranium (HEU) provide separable signatures because fast neutron multiplication is much higher in HEU.

Paper Details

Date Published: 27 August 2010
PDF: 14 pages
Proc. SPIE 7805, Hard X-Ray, Gamma-Ray, and Neutron Detector Physics XII, 78050P (27 August 2010); doi: 10.1117/12.862598
Show Author Affiliations
Leon Forman, Ion Focus Technology, Inc. (United States)
Istvan Dioszegi, Brookhaven National Lab. (United States)
Peter E. Vanier, Brookhaven National Lab. (United States)

Published in SPIE Proceedings Vol. 7805:
Hard X-Ray, Gamma-Ray, and Neutron Detector Physics XII
Arnold Burger; Larry A. Franks; Ralph B. James, Editor(s)

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