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Nishida, Akemi; Murakami, Takahiro*; Satoda, Akira*; Asano, Yuya*; Guo, Z. H.*; Oshima, Masami*; Matsukawa, Keisuke*; Nakajima, Norihiro
Transactions of the 26th International Conference on Structural Mechanics in Reactor Technology (SMiRT-26) (Internet), 10 Pages, 2022/07
no abstracts in English
Nishida, Akemi; Murakami, Takahiro*; Satoda, Akira*; Asano, Yuya*; Guo, Z.*; Matsukawa, Keisuke*; Oshima, Masami*; Nakajima, Norihiro
Transactions of the 25th International Conference on Structural Mechanics in Reactor Technology (SMiRT-25) (USB Flash Drive), 10 Pages, 2019/08
Exhaustive studies on external events that may pose a threat to the structures of nuclear facilities and evaluations of the structural integrities are critical to safety. One of the components that greatly influence the behavior of the plant structure is the connection of structural members. In particular, the modeling of the connections has relied on empirical methods, and been conservatively designed and evaluated by considering them as pinned or rigid connections. Therefore, in this research, we have aimed to develop a connection modeling method that reproduces more realistic behavior by utilizing a three-dimensional model of the connection. As the first step of this research, we planned to determine the stiffness of the connections of steel structural members. The results confirmed that the connection can be regarded as a partially-restrained connection depending on the connection specifications of the structure, and the prospects for realistic stiffness evaluation of the connection were determined.
Imazono, Takashi; Koike, Masato; Kawachi, Tetsuya; Hasegawa, Noboru; Koeda, Masaru*; Nagano, Tetsuya*; Sasai, Hiroyuki*; Oue, Yuki*; Yonezawa, Zeno*; Kuramoto, Satoshi*; et al.
Applied Optics, 51(13), p.2351 - 2360, 2012/05
Times Cited Count：12 Percentile：52.47(Optics)Laminar and blazed types holographic varied-line-spacing spherical gratings for use in a versatile soft X-ray flat-field spectrograph attached to an electron microscope are designed, fabricated, and evaluated. The absolute diffraction efficiencies of laminar (or blazed) master and replica gratings at 86.00
incidence evaluated by synchrotron radiation show over 5% (or 8%) in the 50-200 eV range with the maxima of 22% (or 26-27%). Also the resolving power evaluated by a laser produced plasma source is in excess of 700 at the energy near the 
emission spectrum of lithium (
55 eV) for all gratings. Moreover, the emission spectrum of metallic Li with high spectral resolution is successfully observed with the spectrograph attached to a transmission electron microscope.
emission spectrum of LiImazono, Takashi; Koike, Masato; Kawachi, Tetsuya; Hasegawa, Noboru; Koeda, Masaru*; Nagano, Tetsuya*; Sasai, Hiroyuki*; Oue, Yuki*; Yonezawa, Zeno*; Kuramoto, Satoshi*; et al.
Memoirs of the SR Center Ritsumeikan University, (14), p.131 - 144, 2012/05
We have developed a wavelength-dispersive soft X-ray spectrograph covering an energy region of 50-4000 eV to attach to a conventional electron microscope. The energy range was properly divided into four ranges of 50-200 eV, 155-350 eV, 300-2200 eV, and 2000-4000 eV, and a versatile spectrograph equipped with interchangeable multiple gratings optimized in the respective energy ranges has been developed. In particular, the grating that covers the 50-200 eV range can be used for the measurement of the emission spectrum ( 55 eV) of lithium. The diffraction efficiency evaluated by synchrotron radiation and resolving power measured by laser produced plasma sources are over 5% and in excess of 700, respectively. The emission spectrum of metallic Li with high spectral resolution has been successfully observed with the spectrograph attached to a transmission electron microscope.
Machida, Akihiko; Honda, Mitsunori*; Hattori, Takanori; Sano, Asami; Watanuki, Tetsu; Katayama, Yoshinori; Aoki, Katsutoshi; Komatsu, Kazuki*; Arima, Hiroshi*; Oshita, Hidetoshi*; et al.
Physical Review Letters, 108(20), p.205501_1 - 205501_5, 2012/05
Times Cited Count：18 Percentile：67.41(Physics, Multidisciplinary)Hydrogen atoms absorbed in a metal occupy the interstitial sites of the metal lattice. In an fcc metal lattice, each metal atom has two tetrahedral (T) and one octahedral (O) sites that can accommodate hydrogen. Rare-earth metal La forms T-site occupied LaH
and fully occupied LaH
. O-site occupied or NaCl-type monohydride has yet to be reported for rare-earth metals. Previous X-ray diffraction measurements revealed the pressure-induced decomposition of an fcc-LaH
into H-rich and H-poor phases around 11 GPa. The present neutron diffraction measurements on LaD confirm the formation of NaCl-type LaD as a counterpart of the D-rich LaD
by disproportionation. First-principle calculations demonstrate that the NaCl-type LaH is stabilized at high pressures. Finding the NaCl-type LaH will pave the way for investigations on the site-dependent nature of hydrogen-metal interactions.
Ishino, Masahiko; Koike, Masato; Sato, Futami*; Terauchi, Masami*; Sano, Kazuo*; Sasai, Hiroyuki*
Journal of Applied Physics, 104(7), p.073520_1 - 073520_5, 2008/10
Times Cited Count：0 Percentile：0(Physics, Applied)The multilayer gratings were fabricated by depositing the Co/Si and Co/SiO multilayers onto the surface of laminar-type holographic gratings having shallow grooves. The structures of multilayer gratings observed by a transmission electron microscope showed the well defined structures without serious defects. The structural property evaluated by comparing the measured and calculated diffraction conditions i.e., incidence and diffraction angles, resulted that the diffraction conditions of multilayer gratings were affected by the refractive indices of multilayer coatings even at the photon energy of 8.05 keV. The measured low diffraction efficiencies for the Co/Si multilayer grating in the photon energy range of 1-2 keV would be attributed to the large inter-diffusion in the Co/Si multilayer coating.
multilayers for use in the soft X-ray regionIshino, Masahiko; Koike, Masato; Kanehira, Mika*; Sato, Futami*; Terauchi, Masami*; Sano, Kazuo*
Journal of Applied Physics, 102(2), p.023513_1 - 023513_5, 2007/07
Times Cited Count：6 Percentile：26.43(Physics, Applied)The heat stability of Co/SiO multilayers was evaluated. Multilayer samples were deposited on Si substrates by means of the ion beam sputtering method and annealed at temperatures from 100-600 
C in a vacuum furnace. For the structural and optical evaluations, small angle X-ray diffraction measurements, soft X-ray reflectivity measurement in the 1 keV energy region, and transmission electron microscopy observations were carried out. As the results, the Co/SiO multilayers annealed up to 400 C maintained the initial multilayer structure and kept almost the same X-ray reflectivity as the as-deposited sample. A deterioration of the multilayer structure caused by the growth of Co grains was found on the samples annealed over 500 C, and the soft X-ray reflectivity dropped in accordance with the deterioration of the multilayer structure.
Okumura, Susumu; Arakawa, Kazuo; Fukuda, Mitsuhiro; Nakamura, Yoshiteru; Yokota, Wataru; Ishimoto, Takayuki*; Kurashima, Satoshi; Ishibori, Ikuo; Nara, Takayuki; Agematsu, Takashi; et al.
Review of Scientific Instruments, 76(3), p.033301_1 - 033301_6, 2005/03
Times Cited Count：9 Percentile：43.09(Instruments & Instrumentation)A magnetic field drift, gradual decrease of the order of 10
in several tens of hours, was observed with the beam intensity decrease in an operation of an azimuthally-varying-field (AVF) cyclotron. From our experimental results, we show that the temperature increase of the magnet iron by the heat transfer from the excitation coils can induce such change of the magnetic field as to deteriorate the beam quality. The temperature control of the magnet iron was realized by thermal isolation between the main coil and the yoke and by precise control of the cooling water temperature of the trim coils attached to the pole surfaces in order to prevent temperature change of the magnet iron. The magnetic field stability of 
5
10
and the beam intensity stability of 2% have been achieved by this temperature control.
multilayer opticsIshino, Masahiko; Koike, Masato; Kanehira, Mika*; Sato, Futami*; Terauchi, Masami*; Sano, Kazuo*; Heimann, P. A.*; Gullikson, E. M.*
no journal, ,
no abstracts in English
Aoki, Katsutoshi; Machida, Akihiko; Honda, Mitsunori; Hattori, Takanori; Sano, Asami; Watanuki, Tetsu; Katayama, Yoshinori; Komatsu, Kazuki*; Arima, Hiroshi; Otomo, Toshiya*; et al.
no journal, ,
Neutron diffraction measurements have revealed that LaD undergoes phase separation at high pressure with the relocation of deuterium atoms in the interstitial sites of La metal lattice. Deuterium atoms, which occupy the tetrahedral sites of the fcc metal lattice in LaD, move into the empty octahedral sites at 11 GPa to form LaD and LaD
both having fcc metal lattices. Mono-hydride with an NaCl structure, which is common for mono-hydrides of transition metals, is formed in rare-earth metals for the first time. The first-principle calculations showed that LaH is stable at low pressure and it undergoes a phase separation into LaH and LaH at 10 GPa, which is excellent agreement with the experimental results. Enthalpy comparison shows that unusual volume contraction in LaH than LaH explains the phase separation phenomena. Lattice dynamics calculations on these lanthanum hydrides shed light on the detailed mechanism.
Aoki, Katsutoshi; Machida, Akihiko; Honda, Mitsunori; Hattori, Takanori; Sano, Asami; Watanuki, Tetsu; Katayama, Yoshinori; Komatsu, Kazuki*; Arima, Hiroshi; Otomo, Toshiya*; et al.
no journal, ,
Synchrotron X-ray and neutron diffraction measurements have revealed that LaD undergoes phase separation at high pressure with the relocation of deuterium atoms in the interstitial sites of La metal lattice. Synchrotron X-ray and neutron experiments were made at BL22XU, SPring-8 and a total scattering device, NOVA, J-PARC. Deuterium atoms, which occupy the tetrahedral sites of the fcc metal lattice in LaD, move into the empty octahedral sites at 11 GPa to form LaD and LaD both having fcc metal lattices. Mono-hydride with an NaCl structure, which is common for mono-hydrides of transition metals, is formed in rare-earth metals for the first time. The first-principle calculations showed that LaH is stable at low pressure and it undergoes a phase separation into LaH and LaH at 10 GPa, which is excellent agreement with the experimental results.
Machida, Akihiko; Honda, Mitsunori; Hattori, Takanori; Sano, Asami; Watanuki, Tetsu; Katayama, Yoshinori; Aoki, Katsutoshi; Komatsu, Kazuki*; Arima, Hiroshi; Oshita, Hidetoshi*; et al.
no journal, ,
Formation of an NaCl-type mono-deuteride LaD has been found by neutron diffraction experiments at high pressure. The NaCl-type structure has been reported for alkaline hydrides and transition metal hydrides, but not for rare-earth metal hydrides. The NaCl-type mono-hydride is formed in rare-earth metals for the first time. Lanthanum mono-deuteride is formed as a result of the phase separation of the di-deuteride under high pressure. This result suggests that the three different hydrides, mono-, di-, and tri-hydrides, with the fcc metal lattice are realized. The hydrogen atoms occupy only O-sites, only T-sites and both O-sites and T-sites in the mono-, di-, and tri-hydrides, respectively. Hence, it is expected that the H-M bonding nature is different for each hydride.
Machida, Akihiko; Honda, Mitsunori; Hattori, Takanori; Sano, Asami; Watanuki, Tetsu; Katayama, Yoshinori; Aoki, Katsutoshi; Komatsu, Kazuki*; Arima, Hiroshi; Oshita, Hidetoshi*; et al.
no journal, ,
We have investigated the pressure-induced phase separation in rare-earth metal dihydrides by synchrotron radiation X-ray diffraction and neutron diffraction experiments. Rare-earth metal hydrides exhibit the stoichiometoric dihydride and trihydride. The dihydride is a metallic while trihydride is an insulator. Recently, we have found the pressure induced phase separation in the lanthanum dihydride. This phenomenon is understood as the decomposition into the hydrogen-poor and rich phases under high pressure. However, the hydrogen occupancy and position have been unclear yet. Our neutron diffraction experiments have revealed that an NaCl-type mono-deuteride is formed as a counterpart of the deuterium-rich phase.
Imazono, Takashi; Koike, Masato; Kawachi, Tetsuya; Hasegawa, Noboru; Koeda, Masaru*; Nagano, Tetsuya*; Sasai, Hiroyuki*; Oue, Yuki*; Yonezawa, Zeno*; Kuramoto, Satoshi*; et al.
no journal, ,
no abstracts in English
Aoki, Katsutoshi; Machida, Akihiko; Honda, Mitsunori; Hattori, Takanori; Sano, Asami; Watanuki, Tetsu; Katayama, Yoshinori; Komatsu, Kazuki*; Arima, Hiroshi; Otomo, Toshiya*; et al.
no journal, ,
Rare-earth metal La forms T-site occupied fcc-LaH and fully occupied fcc-LaH, the former is metallic and the latter is insulating. Our previous synchrotron X-ray and infrared measurements revealed that the dihydride decomposed into hydrogen-rich and hydrogen-poor phases upon compression to 11 GPa at ambient temperature; the hydrogen rich phase was identified as LaH but the hydrogen composition and occupation sites of the hydrogen-poor phase remained undetermined. The crystal structure of the hydrogen-poor phase was investigated for LaD by neutron diffraction measurement with a total diffractometer NOVA at J-PARC. The formation of NaCl-type LaD as a counterpart of LaD by the decomposition was confirmed from the diffraction profiles. First-principle enthalpy and lattice dynamic calculations have demonstrated that the NaCl-type LaH is stabilized at high pressures.
Imazono, Takashi; Koike, Masato; Kawachi, Tetsuya; Hasegawa, Noboru; Koeda, Masaru*; Nagano, Tetsuya*; Sasai, Hiroyuki*; Oue, Yuki*; Yonezawa, Zeno*; Kuramoto, Satoshi*; et al.
no journal, ,
A novel multilayer mirror has been invented to uniformly enhance the reflectivity in a few keV energy range at a fixed angle of incidence. The structure of the multilayer consists of a B
C/W bilayer with topmost layer of W deposited on a W/BC multilayer with a topmost layer of BC, thus the order is inverted. This multilayer mirror is based on the scheme that the lights in the short and long wavelength ranges are reflected in the bottom and top regions, respectively. It is applied to a multilayer grating (MLG) for the purpose of use in a flat-field spectrograph attached to a conventional electron microscope. The diffraction efficiency is evaluated at the angle of incidence of 88.65
in the energy region of 2-4 keV. It is revealed that the MLG is effective to uniformly enhance the diffraction efficiency.
Machida, Akihiko; Hattori, Takanori; Honda, Mitsunori*; Sano, Asami; Watanuki, Tetsu; Katayama, Yoshinori; Aoki, Katsutoshi; Komatsu, Kazuki*; Arima, Hiroshi*; Oshita, Hidetoshi*; et al.
no journal, ,
We have investigated the structural properties of rare-earth metal hydrides under high pressure. LaH has the CaF type structure in which the H atoms locate at the tetrahedral interstitial sites (T-sites) of the fcc metal lattice. Synchrotron radiation X-ray diffraction and infrared reflection experiments revealed disproportionation reaction of LaH into the H-poor and H-rich phases around 11 GPa. Before the disproportionation reaction, we have found that the fcc metal lattice transformed into tetragonal lattice. The ordering of the H atoms in the octahedral-sites (O-sites) causes the tetragonal distortion of LaH. The tetragonal transformation and successive disproportionation reaction of LaH would closely relate to the inter-site transfer of the H atoms between the T- and O-sites. We have performed the neutron diffraction experiments of LaD to investigate the change of the positions and occupancies of the hydrogen atoms under high pressure.
Machida, Akihiko; Honda, Mitsunori*; Hattori, Takanori; Sano, Asami; Watanuki, Tetsu; Katayama, Yoshinori; Aoki, Katsutoshi; Komatsu, Kazuki*; Arima, Hiroshi*; Oshita, Hidetoshi*; et al.
no journal, ,
Hydrogen atoms absorbed in a metal occupy the interstitial sites of the metal lattice. In an fcc metal lattice, each metal atom has two tetrahedral (T) and one octahedral (O) sites that can accommodate hydrogen. Rare-earth metal La forms T-site occupied LaH and fully occupied LaH. Previous X-ray diffraction measurements revealed the pressure-induced decomposition of an fcc-LaH into H-rich and H-poor phases around 11 GPa. We performed the neutron diffraction measurements on LaD, and found the formation of NaCl-type LaD as a phase separation products. We have first found the NaCl-type rare-earth metal monohydride.
Arai, Yoichi; Sano, Yuichi; Suganuma, Takashi; Hinai, Hiroshi; Ikeda, Akira*; Obata, Masamichi*; Shibata, Atsuhiro; Nomura, Kazunori
no journal, ,
no abstracts in English
Sano, Asami; Ito, Shoichi*; Inoue, Toru*; Noda, Masamichi*
no journal, ,
Mantle is known to have homogeneous hydrogen isotope composition with 
D = -80 -60 per mille based on the analysis of MORB and OIB. The reason of the depletion of deuterium compared to the present ocean has been explained by the existence of isolated primordial reservoir in the mantle, evolution by the subduction of deuterium-poor hydrous mineral through the geological timescale, and addition of cometary water after the formation of ocean. Hydrogen isotope partitioning factor among minerals is a key in these discussions, but little is known under high pressure and high temperature of mantle conditions. In this study we focused on DH partitioning between olivine and wadsleyite, which is a main constituent of upper mantle and mantle transition zone. The fractionation factor decreases with increasing of duration time towards equilibrium. The present result shows that the MTZ plays a role of the deuterium reservoir in the Earth's mantle.
