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Journal Articles

Design for detecting recycling muon after muon-catalyzed fusion reaction in solid hydrogen isotope target

Okutsu, Kenichi*; Yamashita, Takuma*; Kino, Yasushi*; Nakashima, Ryota*; Miyashita, Konan*; Yasuda, Kazuhiro*; Okada, Shinji*; Sato, Motoyasu*; Oka, Toshitaka; Kawamura, Naritoshi*; et al.

Fusion Engineering and Design, 170, p.112712_1 - 112712_4, 2021/09

A muonic molecule which consists of two hydrogen isotope nuclei (deuteron (d) or tritium (t)) and a muon decays immediately via nuclear fusion and the muon will be released as a recycling muon, and start to find another hydrogen isotope nucleus. The reaction cycle continues until the muon ends up its lifetime of 2.2 $$mu$$s. Since the muon does not participate in the nuclear reaction, the reaction is so called a muon catalyzed fusion ($$mu$$CF). The recycling muon has a particular kinetic energy (KE) of the muon molecular orbital when the nuclear reaction occurs. Since the KE is based on the unified atom limit where distance between two nuclei is zero. A precise few-body calculation estimating KE distribution (KED) is also in progress, which could be compared with the experimental results. In the present work, we observed recycling muons after $$mu$$CF reaction.

Journal Articles

Time evolution calculation of muon catalysed fusion; Emission of recycling muons from a two-layer hydrogen film

Yamashita, Takuma*; Okutsu, Kenichi*; Kino, Yasushi*; Nakashima, Ryota*; Miyashita, Konan*; Yasuda, Kazuhiro*; Okada, Shinji*; Sato, Motoyasu*; Oka, Toshitaka; Kawamura, Naritoshi*; et al.

Fusion Engineering and Design, 169, p.112580_1 - 112580_5, 2021/08

A muon ($$mu$$) having 207 times larger mass of electron and the same charge as the electron has been known to catalyze a nuclear fusion between deuteron (d) and triton (t). These two nuclei are bound by $$mu$$ and form a muonic hydrogen molecular ion, dt$$mu$$. Due to the short inter-nuclear distance of dt$$mu$$, the nuclear fusion, d +t$$rightarrow alpha$$ + n + 17.6 MeV, occurs inside the molecule. This reaction is called muon catalyzed fusion ($$mu$$CF). Recently, the interest on $$mu$$CF is renewed from the viewpoint of applications, such as a source of high-resolution muon beam and mono-energetic neutron beam. In this work, we report a time evolution calculation of $$mu$$CF in a two-layered hydrogen isotope target.

Journal Articles

The Possible transition mechanism for the meta-stable phase in the 7xxx aluminium

Bendo, A.*; Matsuda, Kenji*; Nishimura, Katsuhiko*; Nunomura, Norio*; Tsuchiya, Taiki*; Lee, S.*; Marioara, C. D.*; Tsuru, Tomohito; Yamaguchi, Masatake; Shimizu, Kazuyuki*; et al.

Materials Science and Technology, 36(15), p.1621 - 1627, 2020/09

 Times Cited Count:1 Percentile:0(Materials Science, Multidisciplinary)

Metastable phases in aluminum alloys are the primary nano-scale precipitates which have the biggest contribution to the increase in the tangible mechanical properties. The continuous increase in hardness in the 7xxx aluminum alloys is associated with the phase transformation from clusters or GP-zones to the metastable $$eta'$$ phase. The transformation which is structural and compositional should occur following the path of the lowest activation energy. This work is an attempt to gain insight into how the structural transformation may occur based on the shortest route of diffusion for the eventual structure to result in that of $$eta'$$ phase. However, for the compositional transformation to occur, the proposed mechanism may not stand, since it is a prerequisite for the atoms to be at very precise positions in the aluminum lattice, at the very beginning of structural transformation, which may completely differ from that of the GP-zones atomic arrangements.

Journal Articles

An Unreported precipitate orientation relationship in Al-Zn-Mg based alloys

Bendo, A.*; Matsuda, Kenji*; Lervik, A.*; Tsuru, Tomohito; Nishimura, Katsuhiko*; Nunomura, Norio*; Holmestad, R.*; Marioara, C. D.*; Shimizu, Kazuyuki*; Toda, Hiroyuki*; et al.

Materials Characterization, 158, p.109958_1 - 109958_7, 2019/12

 Times Cited Count:9 Percentile:78.99(Materials Science, Multidisciplinary)

Characterization of precipitates in Al-Zn-Mg alloys, using a combination of electron diffraction, bright field transmission electron microscopy and atomic scale scanning transmission electron microscopy imaging revealed the presence of an unreported $$eta$$$$_{13}$$ orientation relationship between the $$eta$$-MgZn$$_2$$ phase and the Al lattice with the following orientation relationship (0001)$$eta$$ $$||$$ (120)$$_{rm Al}$$ and ($$2bar{1}bar{1}0$$)$$eta$$ $$||$$ (001)$$_{rm Al}$$, plate on (120)$$_{rm Al}$$. The precipitate interfaces were observed and analyzed along two projections 90$$^{circ}$$ to one-another. The precipitate coarsening was through the common thickening ledge mechanism. The ledges were significantly stepped along one lateral direction. An interface relaxation model using density functional theory was carried out to explain the precipitate behavior.

Journal Articles

Effect of copper addition on precipitation behavior near grain boundary in Al-Zn-Mg alloy

Matsuda, Kenji*; Yasumoto, Toru*; Bendo, A.*; Tsuchiya, Taiki*; Lee, S.*; Nishimura, Katsuhiko*; Nunomura, Norio*; Marioara, C. D.*; Lervik, A.*; Holmestad, R.*; et al.

Materials Transactions, 60(8), p.1688 - 1696, 2019/08

 Times Cited Count:5 Percentile:46.2(Materials Science, Multidisciplinary)

no abstracts in English

Journal Articles

Characterisation of structural similarities of precipitates in Mg-Zn and Al-Zn-Mg alloys systems

Bendo, A.*; Maeda, Tomoyoshi*; Matsuda, Kenji*; Lervik, A.*; Holmestad, R.*; Marioara, C. D.*; Nishimura, Katsuhiko*; Nunomura, Norio*; Toda, Hiroyuki*; Yamaguchi, Masatake; et al.

Philosophical Magazine, 99(21), p.2619 - 2635, 2019/07

 Times Cited Count:13 Percentile:83.11(Materials Science, Multidisciplinary)

Journal Articles

Abnormally enhanced diamagnetism in Al-Zn-Mg alloys

Nishimura, Katsuhiko*; Matsuda, Kenji*; Lee, S.*; Nunomura, Norio*; Shimano, Tomoki*; Bendo, A.*; Watanabe, Katsumi*; Tsuchiya, Taiki*; Namiki, Takahiro*; Toda, Hiroyuki*; et al.

Journal of Alloys and Compounds, 774, p.405 - 409, 2019/02

 Times Cited Count:3 Percentile:37.05(Chemistry, Physical)

Journal Articles

Optimization of mechanical properties in aluminum alloys $$via$$ hydrogen partitioning control

Toda, Hiroyuki*; Yamaguchi, Masatake; Matsuda, Kenji*; Shimizu, Kazuyuki*; Hirayama, Kyosuke*; Su, H.*; Fujiwara, Hiro*; Ebihara, Kenichi; Itakura, Mitsuhiro; Tsuru, Tomohito; et al.

Tetsu To Hagane, 105(2), p.240 - 253, 2019/02

 Times Cited Count:0 Percentile:0(Metallurgy & Metallurgical Engineering)

no abstracts in English

Journal Articles

Microstructure evolution in a hydrogen charged and aged Al-Zn-Mg alloy

Bendo, A.*; Matsuda, Kenji*; Lee, S.*; Nishimura, Katsuhiko*; Toda, Hiroyuki*; Shimizu, Kazuyuki*; Tsuru, Tomohito; Yamaguchi, Masatake

Materialia, 3, p.50 - 56, 2018/11

Journal Articles

Element specific electronic states and spin-flip-like behavior of Ce in (Ce$$_{0.2}$$Gd$$_{0.8}$$)Ni composed of heavy fermion CeNi and ferri-magnet GdNi through XMCD method

Yano, Kazuo*; Okane, Tetsuo; Takeda, Yukiharu; Yamagami, Hiroshi; Fujimori, Atsushi; Nishimura, Katsuhiko*; Sato, Kiyoo*

Physica B; Condensed Matter, 515, p.118 - 125, 2017/06

 Times Cited Count:1 Percentile:8.15(Physics, Condensed Matter)

The electronic states of the three constituent elements in the crystal mixed system between CeNi and GdNi, Ce$$_{0.2}$$Gd$$_{0.8}$$Ni, were investigated by soft X-ray magnetic circular dichroism (XMCD). Not only Gd 4f but also Ni 3d and Ce 4f electrons were magnetic and both magnetic moments of Ni and Ce were coupled anti-parallel to the direction of the Gd magnetic moment. After saturation, Ce magnetic moment decreased over 2 T and this behavior was explained by a spin-flip behavior of the Ce magnetic moment. In addition, sum rule analysis has revealed that the magnetic moments of Gd 4 f and Ni 3d electrons could retain small values of orbital magnetic moments.

Journal Articles

X-ray magnetic circular dichroism study of Ce$$_{0.5}$$Gd$$_{0.5}$$Ni

Okane, Tetsuo; Takeda, Yukiharu; Yano, Kazuo*; Fujimori, Atsushi; Yamagami, Hiroshi; Nishimura, Katsuhiko*; Ishikawa, Yoshikazu*; Sato, Kiyoo*

JPS Conference Proceedings (Internet), 3, p.011028_1 - 011028_6, 2014/06

Journal Articles

Evaluation of bending strain dependence of critical current of Nb$$_{3}$$Al conductor for coils with react-and-wind method

Kizu, Kaname; Tsuchiya, Katsuhiko; Shimada, Katsuhiro; Ando, Toshinari*; Hishinuma, Yoshimitsu*; Koizumi, Norikiyo; Matsukawa, Makoto; Miura, Yushi*; Nishimura, Arata*; Okuno, Kiyoshi; et al.

Fusion Engineering and Design, 82(5-14), p.1493 - 1499, 2007/10

 Times Cited Count:3 Percentile:26.87(Nuclear Science & Technology)

no abstracts in English

Journal Articles

Overview of national centralized tokamak program; Mission, design and strategy to contribute ITER and DEMO

Ninomiya, Hiromasa; Akiba, Masato; Fujii, Tsuneyuki; Fujita, Takaaki; Fujiwara, Masami*; Hamamatsu, Kiyotaka; Hayashi, Nobuhiko; Hosogane, Nobuyuki; Ikeda, Yoshitaka; Inoue, Nobuyuki; et al.

Journal of the Korean Physical Society, 49, p.S428 - S432, 2006/12

To contribute DEMO and ITER, the design to modify the present JT-60U into superconducting coil machine, named National Centralized Tokamak (NCT), is being progressed under nationwide collaborations in Japan. Mission, design and strategy of this NCT program is summarized.

Journal Articles

Effects of tensile and compressive strain on critical currents of Nb$$_{3}$$Al strand and cable-in-conduit conductor

Kizu, Kaname; Tsuchiya, Katsuhiko; Shimada, Katsuhiro; Ando, Toshinari*; Hishinuma, Yoshimitsu*; Koizumi, Norikiyo; Matsukawa, Makoto; Miura, Yushi*; Nishimura, Arata*; Okuno, Kiyoshi; et al.

IEEE Transactions on Applied Superconductivity, 16(2), p.872 - 875, 2006/06

 Times Cited Count:1 Percentile:12.39(Engineering, Electrical & Electronic)

no abstracts in English

Journal Articles

Overview of the national centralized tokamak programme

Kikuchi, Mitsuru; Tamai, Hiroshi; Matsukawa, Makoto; Fujita, Takaaki; Takase, Yuichi*; Sakurai, Shinji; Kizu, Kaname; Tsuchiya, Katsuhiko; Kurita, Genichi; Morioka, Atsuhiko; et al.

Nuclear Fusion, 46(3), p.S29 - S38, 2006/03

 Times Cited Count:13 Percentile:44.28(Physics, Fluids & Plasmas)

The National Centralized Tokamak (NCT) facility program is a domestic research program for advanced tokamak research to succeed JT-60U incorporating Japanese university accomplishments. The mission of NCT is to establish high beta steady-state operation for DEMO and to contribute to ITER. The machine flexibility and mobility is pursued in aspect ratio and shape controllability, feedback control of resistive wall modes, wide current and pressure profile control capability for the demonstration of the high-b steady state.

Journal Articles

Engineering design and control scenario for steady-state high-beta operation in national centralized tokamak

Tsuchiya, Katsuhiko; Akiba, Masato; Azechi, Hiroshi*; Fujii, Tsuneyuki; Fujita, Takaaki; Fujiwara, Masami*; Hamamatsu, Kiyotaka; Hashizume, Hidetoshi*; Hayashi, Nobuhiko; Horiike, Hiroshi*; et al.

Fusion Engineering and Design, 81(8-14), p.1599 - 1605, 2006/02

 Times Cited Count:1 Percentile:10.64(Nuclear Science & Technology)

no abstracts in English

Journal Articles

Design study of national centralized tokamak facility for the demonstration of steady state high-$$beta$$ plasma operation

Tamai, Hiroshi; Akiba, Masato; Azechi, Hiroshi*; Fujita, Takaaki; Hamamatsu, Kiyotaka; Hashizume, Hidetoshi*; Hayashi, Nobuhiko; Horiike, Hiroshi*; Hosogane, Nobuyuki; Ichimura, Makoto*; et al.

Nuclear Fusion, 45(12), p.1676 - 1683, 2005/12

 Times Cited Count:15 Percentile:48.09(Physics, Fluids & Plasmas)

Design studies are shown on the National Centralized Tokamak facility. The machine design is carried out to investigate the capability for the flexibility in aspect ratio and shape controllability for the demonstration of the high-beta steady state operation with nation-wide collaboration, in parallel with ITER towards DEMO. Two designs are proposed and assessed with respect to the physics requirements such as confinement, stability, current drive, divertor, and energetic particle confinement. The operation range in the aspect ratio and the plasma shape is widely enhanced in consistent with the sufficient divertor pumping. Evaluations of the plasma performance towards the determination of machine design are presented.

JAEA Reports

Study on Radiation Dose from Vitrified Waste

WAKASUGI, Keiichiro; Miyahara, Kaname; Makino, Hitoshi; Ishiguro, Katsuhiko; Sawamura, Hidenori*; Neyama, Atsushi*; Nishimura, Kazuya*

JNC TN8400 2003-022, 84 Pages, 2003/11

JNC-TN8400-2003-022.pdf:9.58MB

The radiation dose from the vitrified waste which is the same specification set in the Reference Case of the second progress report (H12 report) was evaluated quantitatively taking into account of the shield of the canister and the overpack. In order to understand the feature of radiation dose from the vitrified waste in terms of shielding, the thickness of the concrete shield to decrease less than safety standard for a radiation controlled zone was evaluated. Main results are summarized as follows. (1)The effective dose rates in the case considering the vitrified waste and the canister decrease approximate 4$$sim$$5 orders of magnitude during the period of 1,000 years after vitrification due to decay of short half-life radionuclides. The effective dose rate doesn't decrease from 1,000 to 10,000 years. (2)The effective dose rates at the outside of overpack in the case considering the vitrified waste, canister and overpack are smaller than those inside of overpack approximate 5 orders of magnitude during the period of 100 years due to shielding effect of the overpack. However this difference is relatively small after 100 years since the contribution of $$gamma$$ radiation to total effective dose rates decrease due to decay of fission products. (3)Excepting a few cases, the result using the old law (dose equivalent rate) is larger than the result using the new law (effective dose rate). However the difference between these results is less than factor of 1.2. (4)The thickness of the concrete shield required to attenuate the effective dose during the period of 50 years less than safety standard for a radiation controlled zone is calculated as approximate 0.8m$$sim$$1.5m. The important factors to determine the thickness of the concrete shield are the $$gamma$$ radiation in the case of vitrified waste and the canister, and the neutron radiation in the case of vitrified waste, canister and overpack.

Oral presentation

Effects of tensile and compressive strain on critical currents of Nb$$_{3}$$Al strand and cable-in-conduit conductor

Kizu, Kaname; Ando, Toshinari*; Okuno, Kiyoshi; Koizumi, Norikiyo; Shimada, Katsuhiro; Seo, Kazutaka*; Takahata, Kazuya*; Tamai, Hiroshi; Tsuchiya, Katsuhiko; Nishimura, Arata*; et al.

no journal, , 

no abstracts in English

Oral presentation

Dependence of strain on critical current density in a Nb$$_{3}$$Al CIC conductor measured with spring method

Kizu, Kaname; Ando, Toshinari*; Tsuchiya, Katsuhiko; Shimada, Katsuhiro; Matsukawa, Makoto; Tamai, Hiroshi; Koizumi, Norikiyo; Okuno, Kiyoshi; Nishimura, Arata*; Hishinuma, Yoshimitsu*; et al.

no journal, , 

no abstracts in English

33 (Records 1-20 displayed on this page)