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Backwards extrapolation activation diagnostics and their dynamic range for pulsed neutron source measurements

Packer, L.W.; Allan, S.; Bradnam, S.C.; Jednorog, S.; Łaszyńska, E.; Roberts, N.J.; Wilson, C.; Worrall, R. (2020) Backwards extrapolation activation diagnostics and their dynamic range for pulsed neutron source measurements. Fusion Engineering and Design, 160. 111923 ISSN 09203796

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Abstract

Activation materials implanted within radiation detectors can be used to measure pulsed neutron fields. This work develops an instrument concept with the aim to maximise sensitivity to pulsed fusion neutron fields and, using a data-rejection algorithm combined with backwards extrapolation, enable neutron fluence estimates to be made over a large dynamic range. Through high-fidelity modelling of residual temporal emissions, and a parameterised approach, we study the sensitivity to neutrons of a plastic scintillator-Ag foil layer detector concept. For an optimal design we apply paralysable and non-paralysable deadtime models to the predicted response to D-D fusion neutron fields at various neutron field intensities. In high neutron fluence irradiation
scenarios, where deadtime effects are strongly evident, we use our approach to make estimates of the fluence from instrument response data. We discuss the practical applications of such diagnostics used for plasma focus (PF) fusion experiments, such as at the PF-1000U facility in IPPLM, Poland, inertial confinement fusion and pulsed tokamak experiments, for example at MAST-U, where such diagnostics could complement fission counter-based neutron diagnostics in the future. Finally, we show that the calibration of such detection systems may be achieved using relatively low emission rate, steady state neutron sources, with calibration factors that are straightforward to apply to pulsed neutron field measurements.

Item Type: Article
Keywords: activation, neutron, pulsed fields
Subjects: Ionising Radiation > Neutron Metrology
Divisions: Medical, Marine & Nuclear
Identification number/DOI: 10.1016/j.fusengdes.2020.111923
Last Modified: 01 Jul 2021 14:06
URI: http://eprintspublications.npl.co.uk/id/eprint/9194

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