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anisotropic triangular antiferromagnet Ca
ReO
Cl
Nawa, Kazuhiro*; Hirai, Daigoro*; Kofu, Maiko; Nakajima, Kenji; Murasaki, Ryo*; Kogane, Satoshi*; Kimata, Motoi*; Nojiri, Hiroyuki*; Hiroi, Zenji*; Sato, Taku*
Physical Review Research (Internet), 2(4), p.043121_1 - 043121_11, 2020/12
The spin excitations of the 
= anisotropic triangular antiferromagnet CaReOCl were investigated by inelastic neutron-scattering experiments. The spin excitation spectrum exhibits sharp dispersive modes in addition to a spinonlike continuum. The consistency with the simulated spectrum based on the random-phase approximation is better for CaReOCl than for CsCuCl
, indicating that the spin system in the former remains closer to a Tomonaga-Luttinger liquidlike disordered state.
Nawa, Kazuhiro*; Tanaka, Kimihito*; Kurita, Nubuyuki*; Sato, Taku*; Sugiyama, Haruki*; Uekusa, Hidehiro*; Kawamura, Seiko; Nakajima, Kenji; Tanaka, Hidekazu*
Nature Communications (Internet), 10, p.2096_1 - 2096_8, 2019/05
Times Cited Count：16 Percentile：74.55(Multidisciplinary Sciences)Search for topological materials has been actively promoted in the field of condensed matter physics for their potential application in energy-efficient information transmission and processing. Recent studies have revealed that topologically invariant states, such as edge states in topological insulators, can emerge not only in a fermionic electron system but also in a bosonic system, enabling nondissipative propagation of quasiparticles. Here we report the topologically nontrivial triplon bands measured by inelastic neutron scattering on the spin-1/2 two-dimensional dimerized antiferromagnet BaCuSiO
Cl. The excitation spectrum exhibits two triplon bands that are clearly separated by a band gap due to a small alternation in interdimer exchange interaction, consistent with a refined crystal structure. By analytically modeling the triplon dispersion, we show that BaCuSiOCl is the first bosonic realization of the coupled Su-Schrieffer-Heeger model, where the presence of topologically protected edge states is prompted by a bipartite nature of the lattice.
Magome, Hirokatsu; Okada, Yuji; Tomita, Kenji; Iida, Kazuhiro; Ando, Hitoshi; Yonekawa, Akihisa; Ueda, Haruyasu; Hanawa, Hiroshi; Kanno, Masaru; Sakuta, Yoshiyuki
JAEA-Technology 2015-025, 100 Pages, 2015/09
JAEA-Technology-2015-025.pdf:78.32MB
In Japan Atomic Energy Agency, in order to solve the problem in the long-term operation of a light water reactor, preparation which does the irradiation experiment of light-water reactor fuel and material was advanced. JMTR stopped after the 165th operation cycle in August 2006, and is advancing renewal of the irradiation facility towards re-operation. The material irradiation test facility was installed from 2008 fiscal year to 2012 fiscal year in JMTR. The material irradiation test facility is used for IASCC study, and that consists of mainly three equipments. This report is described performance operating test of the water environmental control facilities for IASCC study carried out 2013 fiscal year.
Magome, Hirokatsu; Okada, Yuji; Hanawa, Hiroshi; Sakuta, Yoshiyuki; Kanno, Masaru; Iida, Kazuhiro; Ando, Hitoshi; Yonekawa, Akihisa; Ueda, Haruyasu; Shibata, Mitsunobu
JAEA-Technology 2014-023, 267 Pages, 2014/07
JAEA-Technology-2014-023-01.pdf:103.68MBJAEA-Technology-2014-023-02.pdf:71.92MB
In Japan Atomic Energy Agency, in order to solve the problem in the long-term operation of a light water reactor, preparation which does the irradiation experiment of light-water reactor fuel and material was advanced. JMTR stopped after the 165th operation cycle in August 2006, and is advancing renewal of the irradiation facility towards re-operation. The material irradiation test facility was installed from 2008 fiscal year to 2012 fiscal year in JMTR. This report summarizes manufacture and installation of the material irradiation test facility for IASCC research carried out from 2012 to 2014 in the follow-up report reported before (JAEA-Technology 2013-019).
Okada, Yuji; Magome, Hirokatsu; Hanawa, Hiroshi; Omi, Masao; Kanno, Masaru; Iida, Kazuhiro; Ando, Hitoshi; Shibata, Mitsunobu; Yonekawa, Akihisa; Ueda, Haruyasu
JAEA-Technology 2013-019, 236 Pages, 2013/10
JAEA-Technology-2013-019.pdf:45.07MB
In Japan Atomic Energy Agency, in order to solve the problem in the long-term operation of a light water reactor, preparation which does the irradiation experiment of light-water reactor fuel and material is advanced. JMTR stopped after the 165th operation cycle in August 2006, and is advancing renewal of the irradiation facility towards re-operation. This material irradiation test facility and power ramping test facility for doing the neutron irradiation test of the fuel and material for light water reactors is scheduled to be manufactured and installed between the 2008 fiscal year and the 2012 fiscal year. This report summarizes manufacture and installation of the material irradiation test facility for IASCC research carried out from the 2008 fiscal year to the 2010 fiscal year.
Okada, Yuji; Magome, Hirokatsu; Iida, Kazuhiro; Hanawa, Hiroshi; Omi, Masao
UTNL-R-0483, p.10_4_1 - 10_4_10, 2013/03
In JAEA(Japan Atomic Energy Agency), about the irradiation embrittlement of the reactor pressure vessel and the stress corrosion cracking of reactor core composition apparatus concerning the long-term use of the light water reactor (BWR), in order to check the influence of the temperature, pressure, and water quality, etc on BWR condition. The water environmental control facility which performs irradiation assisted stress corrosion-cracking (IASCC) evaluation under BWR irradiation environment was fabricated in JMTR. (Japan Materials Testing Reactor). This report is described the outline of manufacture of the water environmental control facility for doing an irradiation test using the saturation temperature capsule after JMTR re-operation.
Shibata, Taiju; Sumita, Junya; Tada, Tatsuya; Hanawa, Satoshi; Sawa, Kazuhiro; Iyoku, Tatsuo
Journal of Nuclear Materials, 381(1-2), p.165 - 170, 2008/10
Times Cited Count：14 Percentile：66.71(Materials Science, Multidisciplinary)The lifetime extension of in-core graphite components is one of the key technologies for the VHTR. The residual stress in the graphite components caused by neutron irradiation at high temperatures affects their lifetime. Although oxidation damage in the components would not be significant in reactor normal operation, it should be checked as well. To evaluate the degradation of the graphite components directly by non-destructive way, the applicability of the micro-indentation and ultrasonic wave methods were investigated. The fine-grained isotropic graphites of IG-110 and IG-430, the candidate grades for the VHTR, were used in this study. The following results were obtained. (1) The micro-indentation behavior was changed by applying the compressive strain on the graphite. It suggested that the residual stress would be measured directly. (2) The change of ultrasonic wave velocity with 1 MHz by the uniform oxidation could be evaluated by the wave-propagation analysis with wave-pore interaction model. (3) The trend of oxidation-induced strength degradation on IG-110 was expressed by using the proposed uniform oxidation model. The importance of the un-uniformity consideration was indicated.
Sumita, Junya; Shibata, Taiju; Hanawa, Satoshi; Ishihara, Masahiro; Iyoku, Tatsuo; Sawa, Kazuhiro
JAEA-Technology 2006-048, 19 Pages, 2006/10
JAEA-Technology-2006-048.pdf:1.37MB
IG-110 graphite is a fine-grained isotropic and nuclear-grade graphite with excellent resistivity on both irradiation and corrosion and with high strength. The IG-110 graphite is used for the graphite components of High Temperature Engineering Test Reactor (HTTR) such as fuel and control rod guide blocks and support posts. In order to design and fabricate the graphite components in the HTTR, the Japan Atomic Energy Research Institute (the Japan Atomic Energy Agency at present) had established the graphite structural design code and design data on the basis of former research results. This report summarized the characteristics of the first loaded IG-110 graphite as basic data for surveillance test, measuring material characteristics changed by neutron irradiation and oxidation. By comparing the design data, it was shown that the first loaded IG-110 graphite had excellent strength properties and enough safety margins to the stress limits in the design code.
Hanawa, Satoshi; Ishihara, Masahiro; Shibata, Taiju; Sawa, Kazuhiro; Motohashi, Yoshinobu*
Zairyo, 55(9), p.868 - 873, 2006/09
no abstracts in English
Sumita, Junya; Hanawa, Satoshi; Shibata, Taiju; Tada, Tatsuya; Iyoku, Tatsuo; Sawa, Kazuhiro
Proceedings of 14th International Conference on Nuclear Engineering (ICONE-14) (CD-ROM), 8 Pages, 2006/07
An analytical study on micro-indentation method to integrity evaluation for graphite components was carried out. The indentation method is used as simplicity test to measure mechanical properties of materials. This method is thought to be applicable to evaluate the residual stress from the relationship between indentation load and indentation depth. In this study, in order to confirm the applicability of the micro-indentation method for lifetime evaluation of the graphite component, indentation load-depth behavior under stress/strain condition was evaluated taking account of the specified minimum ultimate strength of IG-110 graphite. Moreover, analytical investigations of indentation load-depth behavior for oxidized graphite and oxidized graphite with residual strain were also carried out. As a result, it can be said that the indentation method is potentially applicable to evaluate the integrity of graphite components.
Hanawa, Satoshi; Shibata, Taiju; Sumita, Junya; Kikuchi, Takayuki; Sawa, Kazuhiro; Ishihara, Masahiro; Iyoku, Tatsuo
Koon Gakkai-Shi, 32(1), p.36 - 42, 2006/01
no abstracts in English
Hanawa, Satoshi; Sumita, Junya; Shibata, Taiju; Ishihara, Masahiro; Iyoku, Tatsuo; Sawa, Kazuhiro
Transactions of 18th International Conference on Structural Mechanics in Reactor Technology (SMiRT-18), p.600 - 605, 2005/08
no abstracts in English
Shibata, Taiju; Sumita, Junya; Hanawa, Satoshi; Tada, Tatsuya; Sawa, Kazuhiro; Ishihara, Masahiro; Iyoku, Tatsuo
no journal, ,
no abstracts in English
Shibata, Taiju; Sumita, Junya; Hanawa, Satoshi; Tada, Tatsuya; Sawa, Kazuhiro; Iyoku, Tatsuo
no journal, ,
no abstracts in English
Sumita, Junya; Hanawa, Satoshi; Shibata, Taiju; Tada, Tatsuya; Iyoku, Tatsuo; Sawa, Kazuhiro
no journal, ,
In order to extend the lifetime of the graphite components in HTGR, an important technical issue on graphite waste was extracted by investigating the method for disposing of graphite waste and an investigation of the technology for confirming integrity of the graphite components was carried out.
(MoO
)(SeO
)Piyawongwatthana, P.; Nawa, Kazuhiro*; Wu, H. C.*; Sato, Taku*
no journal, ,
