Observation of Low-Energy Positron Diffraction Patterns with a Linac-Based Slow-Positron Beam

Wada, Ken; Shirasawa, Tetsuroh; Mochizuki, Izumi; Fujinami, Masanori; Maekawa, M.; Kawasuso, A.; Takahashi, Toshio; Hyodo, Toshio

doi:10.1380/ejssnt.2018.313

Cited by 7 publications

(3 citation statements)

References 29 publications

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“…[35]. Note that the LEED simulator is also applicable to low-energy positron diffraction (LEPD) [36,37], recently developed for structure determination of two-dimensional materials.…”

Section: Low-energy Electron Diffractionmentioning

confidence: 99%

Data-analysis software framework 2DMAT and its application to experimental measurements for two-dimensional material structures

Motoyama,

Yoshimi,

Iwamoto

et al. 2022

Preprint

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An open-source data-analysis framework 2DMAT has been developed for experimental measurements of two-dimensional material structures. 2DMAT offers five analysis methods: (i) Nelder-Mead optimization, (ii) grid search, (iii) Bayesian optimization, (iv) replica exchange Monte Carlo method, and (v) population-annealing Monte Carlo method. Methods (ii) through (v) are implemented by parallel computation, which is efficient not only for personal computers but also for supercomputers. The current version of 2DMAT is applicable to total-reflection high-energy positron diffraction (TRHEPD), surface X-ray diffraction (SXRD), and low-energy electron diffraction (LEED) experiments by installing corresponding forward problem solvers that generate diffraction intensity data from a given dataset of the atomic positions. The analysis methods are general and can be applied also to other experiments and phenomena.

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“…[35]. Note that the LEED simulator is also applicable to low-energy positron diffraction (LEPD) [36,37], recently developed for structure determination of two-dimensional materials.…”

Section: Low-energy Electron Diffractionmentioning

confidence: 99%

Data-analysis software framework 2DMAT and its application to experimental measurements for two-dimensional material structures

Motoyama,

Yoshimi,

Iwamoto

et al. 2022

Preprint

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“…Moreover, the analysis method is applicable to more general cases, since it can handle variables of different physical dimension at the same time, such as the position and the coverage (occupation fraction) of each surface atom. We hope to apply the method to other diffraction experiments for two-dimensional structures, such as surface X-ray diffraction (SXRD), low energy electron diffraction (LEED), low energy positron diffraction (LEPD) [21,22] and other experiments.…”

Section: Generality Of Sensitivity Analysismentioning

confidence: 99%

Data-driven sensitivity analysis in a total-reflection high-energy positron diffraction (TRHEPD) experiment of the Si$_4$O$_5$N$_3$ / 6H-SiC (0001)-($\sqrt{3} \times \sqrt{3}$) R30$^\circ$

Hoshi,

Sakata,

Oie

et al. 2021

Preprint

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The present article proposes a data analysis method for determining surface structures from experimental results, which consists of a non-linear optimization procedure and a sensitivity analysis. This method solves numerically the partial differential equation in the fully-dynamical quantum diffraction theory with many trial surface structures. In the sensitivity analysis, we focused on the experimental uncertainties and the variation over individual fitting parameters, which was analyzed by solving the eigenvalue problem of the variance-covariance matrix. A modern massively parallel supercomputer was used to complete the analysis within a moderate computational time. The sensitivity analysis provides a basis for the choice of variables in the data analysis for practical reliability. The significance of the present analysis method was demonstrated in the structure determination of a Si 4 O 5 N 3 / 6H-SiC( 0001)-(• surface in a total-reflection high-energy positron diffraction (TRHEPD) experiment.Data-driven sensitivity analysis in a total-reflection high-energy positron diffraction (TRHEPD) experiment

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“…Our LEPD system will be described in detail elsewhere [10]. Briefly an overview of the LEPD system is given here together with those of the pulse stretching and the brightness enhancement system.…”

Section: Overview Of the Whole Systemmentioning

confidence: 99%

Progress report on construction of a low-energy positron diffraction (LEPD) experiment station at KEK

et al. 2018

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A low-energy positron diffraction (LEPD) experiment station was developed at the Slow Positron Facility, High Energy Accelerator Research Organization (KEK). An electron-accelerator-based slowpositron beam with an energy of 5 keV was magnetically transported and focused on a transmissiontype Ni remoderator to achieve a 50 eV-500 eV brightness-enhanced beam in a non-magnetic space. A LEPD detector with center holed retarding meshes, Chevron-type microchannel plates, and a delay-line detector (DLD) was installed. A newly developed pulse stretching system was used to stretch the initial positron-pulse width of 1.2 µs to 200 µs-20 ms to avoid multiple hit events within the position analysis time of the DLD.

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Observation of Low-Energy Positron Diffraction Patterns with a Linac-Based Slow-Positron Beam

Cited by 7 publications

References 29 publications

Data-analysis software framework 2DMAT and its application to experimental measurements for two-dimensional material structures

Data-analysis software framework 2DMAT and its application to experimental measurements for two-dimensional material structures

Data-driven sensitivity analysis in a total-reflection high-energy positron diffraction (TRHEPD) experiment of the Si$_4$O$_5$N$_3$ / 6H-SiC (0001)-($\sqrt{3} \times \sqrt{3}$) R30$^\circ$

Progress report on construction of a low-energy positron diffraction (LEPD) experiment station at KEK

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