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| Home > Publications database > Towards the Development of a Compact Very Cold Neutron Source for the High Brilliance Neutron Source (HBS) |
| Conference Presentation (Invited) | FZJ-2025-01921 |
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2025
Abstract: Very cold neutron (VCN) sources present an exciting opportunity for scientists to access unprecedented length and time scales, and achieve improved resolution in neutron experiments [1]. VCNs are defined over a wide spectral range, from 1 meV (9 Å) down to a few hundred neV (> several100 Å). Recent advancements in the development of thermal scattering kernels for candidate verycold neutron (VCN) moderator and reflector materials under the HighNESS project [2] have openedopportunities for exploring conceptual designs of VCN sources tailored to emerging high-intensitycompact accelerator-driven neutron sources (HiCANS) like the High Brilliance Neutron Source (HBS)[3]. In contrast to the expansive moderator designs typical of large reactor and spallation sources,HiCANS, with a smaller source, necessitate highly efficient and compact moderator solutions. Forthe ESS, moderator concepts have been developed based on solid deuterium; however, at the HBS, ahydrogen-rich moderator is required to effectively slow neutrons to the VCN energy range withinthe limited volume that aligns with the HBS footprint. Methane, a well-established and highly efficientneutron moderator is a promising candidate to serve as a VCN moderator since it possessesa desirable low-lying rotor mode at ~ 1 meV. Liquid parahydrogen (l-pH₂) is a known efficient coldneutron moderator since it is able to convert thermal neutrons to cold neutrons via a single interaction.Various geometrical configurations combining methane and l-pH₂ have been considered toharness the complementary properties of both materials in potential designs of a VCN moderatorfor the HBS. Monte Carlo simulations using the PHITS particle transport code were conducted toevaluate the performance of these configurations when fed by the HBS tantalum source. This studypresents a comparative analysis of the results obtained for various moderator geometries consideredwhen compared with a pure, low dimensional l-pH₂ cold source.References[1] J.M Carpenter and B.J. Micklich, ANL (05/42) (2005).[2] V. Santoro et al, (2023). Nuclear Science and Engineering, 198 31–63 (2023)[3] Baggemann J. et al. (2023). Technical Design Report HBS Volume 2 –Target Stations and Moderators.Grafische Medien, Forschungszentrum Jülich GmbH. ISBN 978-3-95806-710-3.
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