Inter atomic force constants of -PbF from diffuse neutron scattering measurement

Xianglian*; Bao, W.*; Guo, T.*; Li, P.*; Sakuma, Takashi*; Igawa, Naoki

International Journal of Innovation in Science and Mathematics, 5(6), p.165 - 167, 2017/11

Diffuse neutron scattering measurements were performed on powder -PbF at 633 K. Oscillatory diffuse scattering intensities were observed and the observed diffuse scattering intensities were explained by including the correlation effects among thermal displacements of atoms. The force constants among first- and second-nearest-neighboring atoms in -PbF calculated from the values of correlation effects and Debye-Waller temperature parameters were determined as 0.36 eV/ at = 2.599 and 0.21 eV/ at = 3.001 AA, respectively.

Estimation of force constants of Al from diffuse neutron scattering measurement

Makhsun*; Hashimoto, Takuya*; Sakuma, Takashi*; Takahashi, Haruyuki*; Kamishima, Osamu*; Igawa, Naoki; Danilkin, S. A.*

Journal of the Physical Society of Japan, 83(7), p.074602_1 - 074602_4, 2014/07

https://doi.org/10.7566/JPSJ.83.074602

The correlations of atomic thermal displacements in Al were obtained from the analysis of diffuse neutron scattering intensity. The interatomic force constants were determined from the correlation effects using a newly introduced equation. The derived force constants and the crystal structure of Al were used to estimate the phonon dispersion relations, phonon density of states, and specific heat by computer simulation. The calculated phonon dispersion relations and specific heat of Al are similar to those obtained from inelastic neutron scattering and specific heat measurements, respectively.

Optical designs of reflection and refraction collection optics for a JT-60SA core Thomson scattering system

Tojo, Hiroshi; Hatae, Takaki; Hamano, Takashi; Sakuma, Takeshi; Itami, Kiyoshi

Review of Scientific Instruments, 84(9), p.093506_1 - 093506_8, 2013/09

https://doi.org/10.1063/1.4821248

Inter-atomic force constants from correlation effects among thermal displacement of atoms in PbTe

Xianglian*; Sakuma, Takashi*; Mohapatra, S. R.*; Uehara, Hiroyuki*; Takahashi, Haruyuki*; Kamishima, Osamu*; Igawa, Naoki

Molecular Simulation, 38(5), p.448 - 451, 2012/04

https://doi.org/10.1080/08927022.2011.569547

Diffuse neutron scattering measurements have been performed on powder PbTe at 10 and 294 K. Oscillatory diffuse scattering intensity is clearly observed at 294 K. Oscillatory form of the diffuse neutron scattering intensity for PbTe was explained on inclusion of correlation effects among thermal displacements of atoms. From the values of correlation effects and Debye-Waller temperature parameter, force constants among the first nearest neighboring atoms was calculated, = 215 eV/nm, and the second ones were =108 eV/nm and = 144 eV/nm at 294 K.

Force constants of Cu crystals from diffuse neutron scattering measurement

Sakuma, Takashi*; Mohapatra, S. R.*; Uehara, Hiroyuki*; Sakai, Ryutaro*; Xianglian*; Takahashi, Haruyuki*; Igawa, Naoki; Basar, K.*

Atom Indonesia, 36(3), p.121 - 124, 2010/12

https://doi.org/10.17146/aij.2010.28

Diffuse neutron scattering measurement on Cu crystals was performed at 10 K and 300 K and the observed diffuse scattering intensities were analyzed by including the correlation effects among thermal displacements of atoms in the theory. Using the values of correlation effects among neighboring atoms and the values of Debye-Waller temperature parameter, force constants among first, second and third nearest neighboring atoms had been evaluated. The estimated values of force constants among first, second and third nearest neighboring atoms of Cu were 5.58, 3.63 and 2.37 eV/ at 300 K, respectively. The relation between correlation effects and the inter-atomic distance is not depending much on the crystal binding types.

Conceptual design of polychromator for Thomson scattering system in JT-60SA

Tojo, Hiroshi; Hatae, Takaki; Sakuma, Takeshi; Hamano, Takashi; Itami, Kiyoshi

Journal of Plasma and Fusion Research SERIES, Vol.9, p.288 - 293, 2010/08

http://www.jspf.or.jp/JPFRS/PDF/Vol9/jpfrs2010_09-288.pdf

Significant loss in transmissivity of the used fiber after the 18 years operations in JT-60U are found. Therefore, an optimization of the filter's configuration of the polychromator in Thomson scattering system for the high performance plasmas in JT-60SA is an essential task. Especially, loss in optical components induced by radiation from neutrons and -ray should be examined. In this paper, an optimization of the filter configuration in the polychromator is executed and expected error degradation due to the radiation damages in the measurements are also estimated with a comparison between used fibers in JT-60U and radiation resistance fibers. In 10 keV, the time evolution of the averaged relative errors for the radiation resistance fibers increase from 35% by . However, for the used fibers in JT-60U, the errors are 78% and they reaches more than 10% in some high conditions, suggesting some difficulties in the measurements.

Diffuse scattering of -PbF

Xianglian*; Sakuma, Takashi*; Basar, K.*; Takahashi, Haruyuki*; Igawa, Naoki

Journal of the Physical Society of Japan, 79(Suppl.A), p.29 - 32, 2010/03

https://doi.org/10.1143/JPSJS.79SA.29

-PbF belongs to cubic structure with disordered arrangements of F atoms and shows high ionic conductivity at high temperature. Neutron diffuse scattering intensity measurement has been performed at 773 K. Strong and oscillatory diffuse scattering intensity has been observed. The diffuse scattering can be explained by the correlation effects among thermal displacements of atoms and the short-range order in disordered arrangements of F atoms.

Correlation effects among thermal displacements of atoms from diffuse neutron scattering measurements

Sakuma, Takashi*; Mohapatra, S. R.*; Yokokawa, Jo*; Shimizu, Norifumi*; Isozaki, Nobuhiro*; Uehara, Hiroyuki*; Xianglian*; Basar, K.*; Takahashi, Haruyuki*; Kamishima, Osamu*; et al.

Proceedings of 12th Asian Conference on Solid State Ionics and 15th Chinese Conference on Solid State Ionics, p.439 - 445, 2010/00

Diffuse neutron scattering intensities from ionic crystals, covalent crystals and metal crystals are analyzed by including the correlation effects among thermal displacements of atoms into the function describing background intensity. The obtained values of correlation effects among first nearest neighboring atoms are 0.7 near room temperature. The values of the correlation effects do not depend much on the type of the crystal binding near room temperature. The values of correlation effects decrease rapidly with the increase of inter-atomic distances. The correlation effects also decrease with the decrease of temperature.

Development of polarization interferometer for Thomson scattering diagnostics in JT-60U

Hatae, Takaki; Howard, J.*; Ebizuka, Noboru*; Hirano, Yoichi*; Koguchi, Haruhisa*; Kitamura, Shigeru; Sakuma, Takeshi; Hamano, Takashi

Journal of Plasma and Fusion Research SERIES, Vol.8, p.680 - 684, 2009/09

A polarization interferometer based on the Fourier transform spectroscopy for the Thomson scattering diagnostics is being developed to evaluate the validity. At the first stage, a dual channel polarization interferometer utilizing a fixed-thickness birefringent plate is developed, and the target and ranges were 1 keV and 510 m, respectively. The electron temperature is successfully measured by the dual channel polarization interferometer in TPE-RX reversed field pinch machine, for the first time. The temperature of the polarization interferometer nearly agrees with that of the filter polychromator. At the second stage, we are developing a multichannel polarization interferometer employing a Wallaston prism to cover wider range of electron temperature. Interferograms of three kinds of light sources are measured by the multichannel polarization interferometer, and those spectra are reconstructed by Fourier transform. In the measurement of a blackbody radiation source using the multichannel polarization interferometer, both ideal and measured spectra agree within 8%.

Inter-atomic distance and temperature dependence of correlation effects among thermal displacements

Xianglian*; Siagian, S.*; Basar, K.*; Sakuma, Takashi*; Takahashi, Haruyuki*; Igawa, Naoki; Ishii, Yoshinobu*

Solid State Ionics, 180(6-8), p.480 - 482, 2009/05

https://doi.org/10.1016/j.ssi.2008.06.009

Correlation effects among thermal vibrations of atoms are very important to realize the thermal properties of materials. We discuss the inter-atomic distance and temperature dependence of the correlation effects in ionic crystal, AgBr, CuBr, CuI and CuCl, by neutron diffraction method. From the Rietveld analysis of those diffraction data the lattice constants and Deby-Waller parameters were determined. The diffuse scattering of diffraction data was analyzed with the correlation effect, . It is found that the is 0.6-0.75 for the inter-atomic distance around 2.5 and 0.4-0.5 for 4 for all ionic crystals. The value of decreases with the decrease of temperature.