Cold neutron production in solid and liquid moderators. II: on the reentrant-hole configuration

Mitsuyasu, Takeshi; Morishima, N.; Nagaya, Yasunobu

doi:10.1016/j.nima.2004.08.097

Cited by 2 publications

(2 citation statements)

References 9 publications

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“…Reentrant holes and their effectiveness have been discussed in much detail and different implementations [6,7]. The unifying conception is to channel more of the coldest neutrons from the center of the moderator volume to the outside than is possible through the bulk moderator material.…”

Section: Output Of Cold Moderatorsmentioning

confidence: 99%

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Conceptual Proposal for Compound Moderators with Preferential Emission Directions

Thomsen

2014

Physics Procedia

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Large spallation neutron facilities share with compact sources the constraint that the moderation of neutrons relies on a random scattering process. Recently, proposals have been made how to furnish cold moderators with some preferential direction for the scattering and the emission of cold neutrons. Propositions presented so far aim primarily at enhancing the emission of moderated neutrons out of the scattering volume. The use of silicon single crystals and nano-structured material has been proposed to boost or suppress scattering along selected directions, respectively. The recent implementation of a beryllium reflector-filter for a hydrogen moderator system at the Manuel Lujan neutron scattering center augmented moderated neutron flux by reflecting thermal neutrons back into a cold moderator. This installation has met with striking success and proved the technical feasibility of selectable preferential provision of cold and thermal neutrons. In this short contribution a tiny scoping study is presented together with a conceptual sketch of a novel moderator set-up. The approach strives to combine the existing results with some additional measures for increasing the primary neutron flux inside a cold moderator. Even base-lining some generic boundary conditions and not taking peculiarities of materials into account, moderator performance can be improved by mere geometrical internal modifications. Conceiving a "pre-moderator" primarily as "primary reflector" appears to offer additional possibilities for optimization. The expectation is that, depending on design and materials' choices, mixed or cold spectra can be obtained, with the flux of demanded neutrons increased along selected directions of preferential emission. Anticipating more extensive confirmative numerical simulations, the obvious next step could be a first test of the proposed concept at a compact neutron source.

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Section: Output Of Cold Moderatorsmentioning

confidence: 99%

“…Somewhat similar configurations featuring many thin channels as a natural extension of a single large reentrant hole have been proposed as "porous" moderators [7]. Studies indicated them to be effective in enhancing the flow of neutrons out of a moderator.…”

Section: Solid Cube With About 10% Holes On the Input Surfacementioning

confidence: 99%

Conceptual Proposal for Compound Moderators with Preferential Emission Directions

Thomsen

2014

Physics Procedia

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Neutronic Design of Neutron Moderator on a Reentrant-hole Configuration for Kyoto University Accelerator-based Neutron Source (KUANS)

Okita

Tasaki

Abe

2020

Transactions of the Atomic Energy Society of Japan

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The Kyoto University Accelerator-based Neutron Source (KUANS) is a compact neutron source that is mainly used for spectrometer and detector development. In addition, it is also suited for experiments to study the neutronic design of moderators owing to the relatively low neutron generation yield by 9 Be (p,n). We present a neutronic design of the neutron moderator on a reentrant-hole configuration for KUANS to enhance the neutron emission, and some experiments are conducted at KUANS for verification. A polyethylene moderator on a reentrant-hole configuration is designed by PHITS calculation and is introduced to KUANS to obtain intense oblong neutron beams. The intensity of the pulsed neutron beam is experimentally measured. The results reveal that the intensity becomes approximately 1.9 times stronger than that of the conventional rectangular design. In addition, the ratio of its intensity to the conventional intensity increases to approximately threefold as the neutron wavelength increases. It is interesting to note that the longer the neutron wavelength, the more efficiently they are extracted from the inside of the moderator owing to the existence of the reentranthole configuration.

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Cold neutron production in solid and liquid moderators. II: on the reentrant-hole configuration

Cited by 2 publications

References 9 publications

Conceptual Proposal for Compound Moderators with Preferential Emission Directions

Conceptual Proposal for Compound Moderators with Preferential Emission Directions

Neutronic Design of Neutron Moderator on a Reentrant-hole Configuration for Kyoto University Accelerator-based Neutron Source (KUANS)

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