Designing an extended energy range single-sphere multi-detector neutron spectrometer

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• 作者：J.M. Gó ; mez-Ros^a ; ^b ; ^{jm.gomezros@ciemat.es} ; R. Bedogni^b ; M. Moraleda^a ; A. Esposito^b ; A. Pola^c ; M.V. Introini^c ; G. Mazzitelli^b ; L. Quintieri^b ; B. Buonomo^b
• 关键词：Neutron spectrometry ; Neutron dosimetry ; Unfolding ; Dysprosium foils
• 刊名：Nuclear Instruments and Methods in Physics Research Section A ; Accelerators ; Spectrometers ; Detectors and Associated Equipment
• 出版年：2012
• 期刊代码：41_01689002
• 类别：ph
• 出版时间：11 June, 2012
• 卷：677
• 期：Complete
• 页码：4-9
• 文件大小：634 K

摘要

This communication describes the design specifications for a neutron spectrometer consisting of 31 thermal neutron detectors, namely Dysprosium activation foils, embedded in a 25 cm diameter polyethylene sphere which includes a 1 cm thick lead shell insert that degrades the energy of neutrons through (n,xn) reactions, thus allowing to extension of the energy range of the response up to hundreds of MeV neutrons. The new spectrometer, called SP² (SPherical SPectrometer), relies on the same detection mechanism as that of the Bonner Sphere Spectrometer, but with the advantage of determining the whole neutron spectrum in a single exposure. The Monte Carlo transport code MCNPX was used to design the spectrometer in terms of sphere diameter, number and position of the detectors, position and thickness of the lead shell, as well as to obtain the response matrix for the final configuration. This work focuses on evaluating the spectrometric capabilities of the SP² design by simulating the exposure of SP² in neutron fields representing different irradiation conditions (test spectra). The simulated SP² readings were then unfolded with the FRUIT unfolding code, in the absence of detailed pre-information, and the unfolded spectra were compared with the known test spectra. The results are satisfactory and allowed approving the production of a prototypal spectrometer.