Coherent Neutron Scattering in Polycrystalline Deuterium and its Implications for Ultracold Neutron Production

Lavelle, C. M.; Salvat, Daniel

doi:10.48550/arxiv.1005.1016

Cited by 4 publications

(15 citation statements)

References 29 publications

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“…The ratios of corrected IA σ -1ph to "old" IA σ IA are given as χ D2 . These ratios compare well with those obtained by Liu et al [26], χ Liu D2 . The scattering cross sections σ Stepanov yielded by the Stepanov formula are shown for comparison.…”

Section: Comparison Of Results Using Different Calculation Methodssupporting

confidence: 92%

“…These should from now on be used in calculations and simulations of UCN upscattering in sD 2 . Our results agree very well with Monte Carlo simulations by Liu et al [26]. This agreement is a mutual confirmation for both results as they were obtained using completely different methods.…”

Section: Discussionsupporting

confidence: 92%

“…Our corrected one-phonon up-scattering cross sections σ -1ph lie less than 14% below those of Liu et al [26], who used a first-principles Monte Carlo calculation of the dynamic structure function S(q, ω) of polycrystalline sD 2 to obtain their results. The excellent agreement of the results from these two very different approaches is a mutual validation and underlines the pertinence of the corrections to the IA presented here.…”

Section: Comparison Of Results Using Different Calculation Methodsmentioning

confidence: 60%

“…As Liu et al [26] have shown, the DOS of sD 2 has two peaks, one at Θ ac D = 70 K due to acoustic phonons and one at Θ opt D = 110 K due to optical phonons. For the PVH treatment of sD 2 , we used the reduced Debye temperature of 70 K, since the approach is only strictly applicable to Bravais-type crystals, i.e., lattices without optical phonon modes.…”

Section: Parameters Of Sd2 For Quantitative Calculationsmentioning

confidence: 91%

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Incoherent approximation for neutron up-scattering cross sections and its corrections for slow neutrons and low crystal temperatures

et al. 2021

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The incoherent approximation (IA) is often used for calculating the one-phonon inelastic neutron scattering cross section for arbitrary solids. It is valid for thermal neutrons but for slow neutrons it requires a correction, which is significant for isotopes that are strong coherent scatterers. In this article, we present the extension of the Placzek-Van Hove corrections for slow neutrons in the limit of low temperatures using the example of solid ortho-deuterium (sD2). Our approach yields realistic one-phonon up-scattering cross sections for sD2 and shows the IA to be a factor of 2 to 5 too high for ultracold neutron (UCN) up-scattering in sD2. Our calculations are compared with previously published Monte Carlo calculations of the one-phonon cross section based on the dynamic structure function S(q, ω) of polycrystalline ortho-deuterium and are found to be consistent with them. Furthermore, we provide the means for easily replicable calculations of the one-phonon up-scattering cross sections of solid ortho-deuterium for slow neutrons. These should from now on be used in calculations and simulations of UCN scattering in sD2.

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Section: Comparison Of Results Using Different Calculation Methodssupporting

confidence: 92%

Section: Discussionsupporting

confidence: 92%

Section: Comparison Of Results Using Different Calculation Methodsmentioning

confidence: 60%

Section: Parameters Of Sd2 For Quantitative Calculationsmentioning

confidence: 91%

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Incoherent approximation for neutron up-scattering cross sections and its corrections for slow neutrons and low crystal temperatures

et al. 2021

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“…Recently a re-evaluation of the neutron scattering in solid deuterium was performed in [25], it was based on the calculations in the frame of a rigorous model of coherent neutron scattering by deuterium nuclei. The resulting scattering cross sections obtained in this work are significantly different from the previous predictions [12,13,15] based on the incoherent approximation.…”

mentioning

confidence: 99%

UCN transport simulation in solid deuterium crystals

Pokotilovski

2012

Nuclear Instruments and Methods in Physics Research Section A:

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The extraction efficiency of ultracold neutrons from cryogenic moderators depends critically on the neutron transparency of the moderator material. A Monte Carlo simulation of the probability of the UCN going out from non-ideal (disordered) solid deuterium crystals has been performed. It was based on the use of a correlation function describing the density fluctuations in a disordered material, the latter being inferred from the measured very low neutron energy total cross sections for this material.Ultracold neutrons [1] (UCN, the energy below ∼ 0.3µeV), which can be contained in closed volumes, have found important applications in the investigation of fundamental properties of the neutron [2].The best UCN source -ILL UCN turbine [3] yields maximum UCN density in a trap of ∼ 50 n/cm 3 and, respectively, the flux ∼ 5 × 10 3 n cm −2 s −1 . Recent years brought hope for significant progress in the intensity of very low energy neutron beams. This is connected with the possible use of the most effective cold moderators: solid deuterium or solid deuterocarbons at low temperatures of ∼ 5 -10 K for production of very cold neutrons.The most promising and popular material for the UCN converter is solid deuterium. The first test of the UCN production in solid deuterium has been performed by the PNPI group [4], which then has been studying experimentally the UCN production in deuterium during many years [5][6][7][8][9][10][11].The first estimate of the UCN production and up-scattering cross sections in solid deuterium was made in [12]. The phonon frequency spectrum of solid deuterium was calculated in [13] using the dispersion relations measured in [14]. Later calculations in the incoherent approximation [15] of the UCN scattering on phonons in solid deuterium reproduced the results of [13], this publication also 1

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HighNESS conceptual design report: Volume I

Santoro,

Abou El Kheir,

Acharya

et al. 2024

JNR

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The European Spallation Source, currently under construction in Lund, Sweden, is a multidisciplinary international laboratory. Once completed to full specifications, it will operate the world’s most powerful pulsed neutron source. Supported by a 3 million Euro Research and Innovation Action within the EU Horizon 2020 program, a design study (HighNESS) has been completed to develop a second neutron source located below the spallation target. Compared to the first source, designed for high cold and thermal brightness, the new source has been optimized to deliver higher intensity, and a shift to longer wavelengths in the spectral regions of cold (CN, 2–20 Å), very cold (VCN, 10–120 Å), and ultracold (UCN, >500 Å) neutrons. The second source comprises a large liquid deuterium moderator designed to produce CN and support secondary VCN and UCN sources. Various options have been explored in the proposed designs, aiming for world-leading performance in neutronics. These designs will enable the development of several new instrument concepts and facilitate the implementation of a high-sensitivity neutron-antineutron oscillation experiment (NNBAR). This document serves as the Conceptual Design Report for the HighNESS project, representing its final deliverable.

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Coherent Neutron Scattering in Polycrystalline Deuterium and its Implications for Ultracold Neutron Production

Cited by 4 publications

References 29 publications

Incoherent approximation for neutron up-scattering cross sections and its corrections for slow neutrons and low crystal temperatures

Incoherent approximation for neutron up-scattering cross sections and its corrections for slow neutrons and low crystal temperatures

UCN transport simulation in solid deuterium crystals

HighNESS conceptual design report: Volume I

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