Low dimensional neutron moderators for enhanced source brightness

Ferenc Mezei, Luca Zanini, Alan Takibayev, Konstantin Batkov, Esben Bryndt Klinkby, Eric Pitcher, Troels Schönfeldt

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    Abstract

    In a recent numerical optimization study we have found that liquid para-hydrogen coupled cold neutron moderators deliver 3–5 times higher cold neutron brightness at a spallation neutron source if they take the form of a flat, quasi 2-dimensional disc, in contrast to the conventional more voluminous shapes used by now. In the present paper we describe a simple theoretical explanation of this unexpected behavior, which is based on the large difference in para-hydrogen between the values of the scattering mean free path for thermal neutrons (in the range of 1 cm) and its much larger equivalent for cold neutrons. This model leads to the conclusions that the optimal shape for high brightness para-hydrogen neutron moderators is the quasi 1-dimensional tube and these low dimensional moderators can also deliver much enhanced cold neutron brightness in fission reactor neutron sources, compared to the much more voluminous liquid D2 or H2 moderators currently used. Neutronic simulation calculations confirm both of these theoretical conclusions.
    Original languageEnglish
    JournalJournal of Neutron Research
    Volume17
    Issue number2
    Pages (from-to)101-105
    ISSN1023-8166
    DOIs
    Publication statusPublished - 2014

    Bibliographical note

    This article is published online with Open Access and distributed under the terms of the Creative Commons Attribution Non-Commercial License

    Keywords

    • cold source
    • neutron moderator
    • neutron scattering
    • Neutron source
    • para-hydrogen
    • research reactor
    • spallation source

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