Title: Evaluation of Lithium Gadolinium Borate Capture-Gated Spectrometer Neutron Efficiencies
Abstract: Accurate determination of neutron dose equivalent requires knowledge of the neutron energy distribution. Existing neutron spectrometers, such as Bonner sphere sets, are typically bulky and require long acquisition times. Hence, a handheld or portable system that could perform area monitoring with acceptable accuracy would be of interest. Such a device will require a detector that is efficient, and possesses gamma-neutron discrimination capabilities. An organic scintillator that contains lithium, gadolinium, and boron, all three of which possess isotopes with large neutron capture cross-sections for highly exothermic reactions, has been recently developed by MSI/Photogenics. This combination of materials provides for the detection of fast neutrons by proton recoil which when used in conjunction with a slow neutron capture gate allows total energy information to be obtained. The system also responds to gamma-rays but n-gamma discrimination techniques allow it to be applied in mixed fields. Photogenics recently completed the full demonstration of a Lithium Gadolinium Borate (LGB) neutron spectrometer's performance under a Department of Homeland Security Domestic Nuclear Detection Office (DNDO) grant. A potential application suggested for this technology is in the identification of shielded fissile materials. A 2" times 2" (50.8 mm times 50.8 mm) sample of composite scintillator, consisting of lithium gadolinium borate crystals in a plastic scintillator matrix, produced by Photogenics has been tested for this purpose. The Tests consist of verifying the n-gamma discrimination and measurements of both capture and capture gated efficiencies using <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">252</sup> Cf and Am-Li neutron sources of various activities under a variety of gamma shielding and neutron attenuation geometries. The results, for this small test sample, showed that in addition to its rudimentary spectroscopic capability, the Photogenics LGB detector has a overall neutron detection efficiency that is attractive for handheld applications.
Publication Year: 2009
Publication Date: 2009-06-01
Language: en
Type: article
Indexed In: ['crossref']
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Cited By Count: 16
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