Neutron guide shielding for the BIFROST spectrometer at ESS

K. Mantulnikovs, M. Bertelsen, C.P. Cooper-Jensen, K. Lefmann, Esben Bryndt Klinkby

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    We report on the study of fast-neutron background for the BIFROST spectrometer
    at ESS. We investigate the effect of background radiation induced by the interaction of fast neutrons from the source with the material of the neutron guide and devise a reasonable fast, thermal/cold neutron shielding solution for the current guide geometry using McStas and MCNPX. We investigate the effectiveness of the steel shielding around the guide by running simulations with three different steel thicknesses. The same approach is used to study the efficiencies of the steel wall a flat cylinder pierced by the guide in the middle and the polyethylene layer. The final model presented here has a 3 cm thick steel shielding around the guide, 30 cm of polyethylene around the shielding, two 5 mm thick B4C layers and a steel wall at position Z = 38 m, being 1 m thick and 10 m in radius. The final model finally proves that it is sufficient to bring the background level below the cosmic neutron rate, which defines an order of magnitude of the lowest obtainable background in the instruments.
    Original languageEnglish
    Title of host publicationVI European Conference on Neutron Scattering (ECNS2015)
    Number of pages12
    PublisherIOP Publishing
    Publication date2016
    Article number012027
    Publication statusPublished - 2016
    Event6th European Conference on Neutron Scattering - Zaragoza, Spain
    Duration: 30 Aug 20154 Sept 2015
    Conference number: 6


    Conference6th European Conference on Neutron Scattering
    SeriesJournal of Physics: Conference Series (Online)


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