The reflection of very cold neutrons from diamond powder nanoparticles

Nesvizhevsky, V. V.; Лычагин, Е. В.; Muzychka, A. Yu.; Strelkov, A. V.; Pignol, G.; Протасов, К. В.

doi:10.1016/j.nima.2008.07.149

Cited by 50 publications

(51 citation statements)

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“…We do not include in our estimate the various methods by which the initial cold neutron brightness might be increased which are the subjects for ongoing research. Examples include neutronics techniques such as a reentrant moderator designs [133], strategic use of neutron reflector/filters [134], supermirror reflectors [123], and non-specular, high-albedo materials such as diamond nanoparticle composites [135][136][137]. Some of these techniques are not suitable for use at multipurpose spallation sources serving a materials science user community, where sharply defined neutron pulses in time may be required.…”

Section: Design Considerations For An Improved N −N Oscillation Searcmentioning

confidence: 99%

Neutron-antineutron oscillations: Theoretical status and experimental prospects

et al. 2016

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The observation of neutrons turning into antineutrons would constitute a discovery of fundamental importance for particle physics and cosmology. Observing the n−n transition would show that baryon number (B) is violated by two units and that matter containing neutrons is unstable. It would provide a clue to how the matter in our universe might have evolved from the B = 0 early universe. If seen at rates observable in foreseeable next-generation experiments, it might well help us understand the observed baryon asymmetry of the universe. A demonstration of the violation of B − L by 2 units would have a profound impact on our understanding of phenomena beyond the Standard Model of particle physics.Slow neutrons have kinetic energies of a few meV. By exploiting new slow neutron sources and optics technology developed for materials research, an optimized search for oscillations using free neutrons from a slow neutron moderator could improve existing limits on the free oscillation probability by at least three orders of magnitude. Such an experiment would deliver a slow neutron beam through a magnetically-shielded vacuum chamber to a thin annihilation target surrounded by a low-background antineutron annihilation detector. Antineutron annihilation in a target downstream of a free neutron beam is such a spectacular experimental signature that an essentially background-free search is possible. An authentic positive signal can be extinguished by a very small change in the ambient magnetic field in such an experiment. It is also possible to improve the sensitivity of neutron oscillation searches in nuclei using large underground detectors built mainly to search for proton decay and detect neutrinos. This paper summarizes the relevant theoretical developments, outlines some ideas to improve experimental searches for free neutron oscillations, and suggests avenues both for theoretical investigation and for future improvement in the experimental sensitivity.

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Section: Design Considerations For An Improved N −N Oscillation Searcmentioning

confidence: 99%

Neutron-antineutron oscillations: Theoretical status and experimental prospects

et al. 2016

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“…On the long-wavelength side of the neutron spectrum, reflections from powders of nano-sized diamond grains have been calculated and demonstrated to augment directional flux of very cold neutrons [13].…”

Section: Output Of Cold Moderatorsmentioning

confidence: 99%

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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“…reflecting material and crystals to be included in the design and optimization of advanced moderators. Examples include the recently proposed Sicrystal vanes [11] or nano-diamond coatings [12], which by using the directly coupled MCNPX-McStas interface could be simulated to a level beyond what is possible with the MCNPX or McStas codes alone. Also we foresee that the combination of MCNPX and McStas will enable more accurate calculation of photon production along neutron guides, and thus ultimately yield better shielding calculations.…”

Section: Prospectsmentioning

confidence: 99%