Cold and thermal neutron scattering cross sections of liquid H2 and D2. II: improvement on coherent scattering

Morishima, N.; Nishikawa, Y.

doi:10.1016/j.anucene.2003.10.010

Cited by 8 publications

(6 citation statements)

References 18 publications

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“…to obtain a direct and reasonable agreement with experiment, comparable with the one obtained with the calculations of Ref. [18], and incomparably better than that of Schott himself (using the IG model) and of Utsuro 23 (both not shown in the figure).…”

Section: Comparison With Experimental Data In the Thermal And Epither...supporting

confidence: 86%

“…Actually, there are evidences that distinct intermolecular contributions influence the neutron signal from para-H 2 and that self calculations are insufficient in certain conditions. 18 A good knowledge of the collective (i.e. coherent) dynamics of this liquid is therefore an essential ingredient to achieve the accuracy demanded nowadays on subthermal neutron cross sections.…”

Section: Rangementioning

confidence: 99%

“…Much work was devoted in past years to the implementation of scattering kernels for the hydrogen liquids 3,[15][16][17][18] with different methods used to effectively evaluate both the self and distinct CM contributions to the DDCS. However, the above mentioned quantum effects were mostly neglected, or accounted for only approximately, or finally included in an effective way by adjustments to pioneering experimental data.…”

Section: Introductionmentioning

confidence: 99%

“…/sr/meV/molecule] Scattered neutron energy E 1 [meV] (Color online) Experimental DDCS of H 2 at 19.8 K with a 41% ortho concentration, (black squares)22 and CMD+GA results (red dots with thin line). The blue empty circles are the DDCS values calculated by Morishima and Nishikawa 18. Measurements refer to the thermal range (E 0 = 21.8 meV) and rather wide angles indicated in each frame.…”

mentioning

confidence: 99%

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Velocity autocorrelation in liquid parahydrogen by quantum simulations for direct parameter-free computations of neutron cross sections

et al. 2015

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Accurate knowledge of the single-molecule (self) translational dynamics of liquid para-H 2 is an essential requirement for the calculation of the neutron scattering properties of this important quantum liquid. We show that, by using Centroid Molecular Dynamics (CMD) quantum simulations of the velocity autocorrelation function, calculations of the total neutron cross section (TCS) remarkably agree with experimental data at the thermal and epithermal incident neutron energies where para-H 2 dynamics is actually dominated by the self contributions. This result shows that a proper account of the quantum nature of the fluid, as provided by CMD, is a necessary and very effective condition to obtain the correct absolute-scale cross section values directly from firstprinciple computations of the double differential cross section, and without the need of introducing any empirically adjusted quantity. At subthermal incident energies, appropriate modeling of the para-H 2 intermolecular (distinct) dynamics also becomes crucial, but quantum simulations are not yet able to cope with it. Existing simple models which account for the distinct part provide an appropriate correction of self-only calculations and bring the computed results in reasonable accord with TCS experimental data available until very recently. However, if just published cross section measurements in the cold range are considered, the agreement turns out to be by far superior and very satisfactory. The possible origin of slight residual differences will be commented and suggest further computational and experimental efforts. Nonetheless, the ability to reproduce the total cross section in the wide range between 1 and 900 meV represents an encouraging and important validation step of the CMD method and of the present simple algorithm.

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Section: Comparison With Experimental Data In the Thermal And Epither...supporting

confidence: 86%

Section: Rangementioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

mentioning

confidence: 99%

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Velocity autocorrelation in liquid parahydrogen by quantum simulations for direct parameter-free computations of neutron cross sections

et al. 2015

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“…The pre-moderator was light water in thickness of 20 mm. The moderator material was liquid para-hydrogen [6,7], and the shape of the moderator surface (mirror) was a "W" (Fig. 3).…”

Section: Numerical Simulation By Phitsmentioning

confidence: 99%

A Diode-like Neutron Mirror for a Cold Neutron Moderator for Use in Neutron Beam Facilities

et al. 2014

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We propose a new type of neutron mirror for a cold moderator to provide a bright collimated beam. The neutron mirror has high reflectivity on its front side and is transparent on its back side. It works like a diode at a small glancing angle, and its use makes it possible to obtain a bright collimated beam by using both the neutron mirror and moderator material. Here we explain the concept of the diode-like neutron mirror and describe its feasibility as tested in a numerical simulation.

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Neutron multigroup cross-sections of moderator materials for cold and ultracold neutron production

Morishima

2007

Nuclear Instruments and Methods in Physics Research Section A:

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Cold and thermal neutron scattering cross sections of liquid H2 and D2. II: improvement on coherent scattering

Cited by 8 publications

References 18 publications

Velocity autocorrelation in liquid parahydrogen by quantum simulations for direct parameter-free computations of neutron cross sections

Velocity autocorrelation in liquid parahydrogen by quantum simulations for direct parameter-free computations of neutron cross sections

A Diode-like Neutron Mirror for a Cold Neutron Moderator for Use in Neutron Beam Facilities

Neutron multigroup cross-sections of moderator materials for cold and ultracold neutron production

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