Fast time correlation detection in associated particle spectrometry of spontaneous fission neutrons and cosmic-ray backgrounds

Leon Forman; Istvan Dioszegi; Peter E. Vanier

doi:10.1117/12.862598

27 August 2010 Fast time correlation detection in associated particle spectrometry of spontaneous fission neutrons and cosmic-ray backgrounds

Leon Forman, Istvan Dioszegi, Peter E. Vanier

Author Affiliations +

Proceedings Volume 7805, Hard X-Ray, Gamma-Ray, and Neutron Detector Physics XII; 78050P (2010) https://doi.org/10.1117/12.862598
Event: SPIE Optical Engineering + Applications, 2010, San Diego, California, United States

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.

Citation Download Citation

Leon Forman, Istvan Dioszegi, and Peter E. Vanier "Fast time correlation detection in associated particle spectrometry of spontaneous fission neutrons and cosmic-ray backgrounds", Proc. SPIE 7805, Hard X-Ray, Gamma-Ray, and Neutron Detector Physics XII, 78050P (27 August 2010); https://doi.org/10.1117/12.862598

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