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Journal Articles

Local electronic structure of interstitial hydrogen in MgH$$_2$$ inferred from muon study

Kadono, Ryosuke*; Hiraishi, Masatoshi*; Okabe, Hirotaka*; Koda, Akihiro*; Ito, Takashi

Journal of Physics; Condensed Matter, 35(28), p.285503_1 - 285503_13, 2023/07

Journal Articles

Sodium-cooled Fast Reactors

Ohshima, Hiroyuki; Morishita, Masaki*; Aizawa, Kosuke; Ando, Masanori; Ashida, Takashi; Chikazawa, Yoshitaka; Doda, Norihiro; Enuma, Yasuhiro; Ezure, Toshiki; Fukano, Yoshitaka; et al.

Sodium-cooled Fast Reactors; JSME Series in Thermal and Nuclear Power Generation, Vol.3, 631 Pages, 2022/07

This book is a collection of the past experience of design, construction, and operation of two reactors, the latest knowledge and technology for SFR designs, and the future prospects of SFR development in Japan. It is intended to provide the perspective and the relevant knowledge to enable readers to become more familiar with SFR technology.

Journal Articles

Dimensional reduction by geometrical frustration in a cubic antiferromagnet composed of tetrahedral clusters

Okuma, Ryutaro*; Kofu, Maiko; Asai, Shinichiro*; Avdeev, M.*; Koda, Akihiro*; Okabe, Hirotaka*; Hiraishi, Masatoshi*; Takeshita, Soshi*; Kojima, Kenji*; Kadono, Ryosuke*; et al.

Nature Communications (Internet), 12, p.4382_1 - 4382_7, 2021/07

 Times Cited Count:5 Percentile:57.28(Multidisciplinary Sciences)

Journal Articles

Thermally altered subsurface material of asteroid (162173) Ryugu

Kitazato, Kohei*; Milliken, R. E.*; Iwata, Takahiro*; Abe, Masanao*; Otake, Makiko*; Matsuura, Shuji*; Takagi, Yasuhiko*; Nakamura, Tomoki*; Hiroi, Takahiro*; Matsuoka, Moe*; et al.

Nature Astronomy (Internet), 5(3), p.246 - 250, 2021/03

 Times Cited Count:30 Percentile:96.87(Astronomy & Astrophysics)

Here we report observations of Ryugu's subsurface material by the Near-Infrared Spectrometer (NIRS3) on the Hayabusa2 spacecraft. Reflectance spectra of excavated material exhibit a hydroxyl (OH) absorption feature that is slightly stronger and peak-shifted compared with that observed for the surface, indicating that space weathering and/or radiative heating have caused subtle spectral changes in the uppermost surface. However, the strength and shape of the OH feature still suggests that the subsurface material experienced heating above 300 $$^{circ}$$C, similar to the surface. In contrast, thermophysical modeling indicates that radiative heating does not increase the temperature above 200 $$^{circ}$$C at the estimated excavation depth of 1 m, even if the semimajor axis is reduced to 0.344 au. This supports the hypothesis that primary thermal alteration occurred due to radiogenic and/or impact heating on Ryugu's parent body.

Journal Articles

Quantum magnetisms in uniform triangular lattices Li$$_{2}$$$$A$$Mo$$_{3}$$O$$_{8}$$ ($$A$$ = In, Sc)

Iida, Kazuki*; Yoshida, Hiroyuki*; Okabe, Hirotaka*; Katayama, Naoyuki*; Ishii, Yuto*; Koda, Akihiro*; Inamura, Yasuhiro; Murai, Naoki; Ishikado, Motoyuki*; Kadono, Ryosuke*; et al.

Scientific Reports (Internet), 9(1), p.1826_1 - 1826_9, 2019/02

 Times Cited Count:8 Percentile:59.99(Multidisciplinary Sciences)

Journal Articles

Progress of divertor simulation research toward the realization of detached plasma using a large tandem mirror device

Nakashima, Yosuke*; Takeda, Hisahito*; Ichimura, Kazuya*; Hosoi, Katsuhiro*; Oki, Kensuke*; Sakamoto, Mizuki*; Hirata, Mafumi*; Ichimura, Makoto*; Ikezoe, Ryuya*; Imai, Tsuyoshi*; et al.

Journal of Nuclear Materials, 463, p.537 - 540, 2015/08

 Times Cited Count:18 Percentile:82.74(Materials Science, Multidisciplinary)

Journal Articles

Dismantlement of large fusion experimental device JT-60U

Ikeda, Yoshitaka; Okano, Fuminori; Sakasai, Akira; Hanada, Masaya; Akino, Noboru; Ichige, Hisashi; Kaminaga, Atsushi; Kiyono, Kimihiro; Kubo, Hirotaka; Kobayashi, Kazuhiro; et al.

Nihon Genshiryoku Gakkai Wabun Rombunshi, 13(4), p.167 - 178, 2014/12

The JT-60U torus was disassembled so as to newly install the superconducting tokamak JT-60SA torus. The JT-60U used the deuterium for 18 years, so the disassembly project of the JT-60U was the first disassembly experience of a fusion device with radioactivation in Japan. All disassembly components were stored with recording the data such as dose rate, weight and kind of material, so as to apply the clearance level regulation in future. The lessons learned from the disassembly project indicated that the cutting technologies and storage management of disassembly components were the key factors to conduct the disassembly project in an efficient way. After completing the disassembly project, efforts have been made to analyze the data for characterizing disassembly activities, so as to contribute the estimation of manpower needs and the radioactivation of the disassembly components on other fusion devices.

Journal Articles

Safe disassembly and storage of radioactive components of JT-60U torus

Ikeda, Yoshitaka; Okano, Fuminori; Hanada, Masaya; Sakasai, Akira; Kubo, Hirotaka; Akino, Noboru; Chiba, Shinichi; Ichige, Hisashi; Kaminaga, Atsushi; Kiyono, Kimihiro; et al.

Fusion Engineering and Design, 89(9-10), p.2018 - 2023, 2014/10

 Times Cited Count:2 Percentile:16.53(Nuclear Science & Technology)

Disassembly of the JT-60U torus was started in 2009 after 18-years D$$_{2}$$ operations, and was completed in October 2012. The JT-60U torus was featured by the complicated and welded structure against the strong electromagnetic force, and by the radioactivation due to D-D reactions. Since this work is the first experience of disassembling a large radioactive fusion device in Japan, careful disassembly activities have been made. About 13,000 components cut into pieces with measuring the dose rates were removed from the torus hall and stored safely in storage facilities by using a total wokers of 41,000 person-days during 3 years. The total weight of the disassembly components reached up to 5,400 tons. Most of the disassembly components will be treated as non-radioactive ones after the clearance verification under the Japanese regulation in future. The assembly of JT-60SA has started in January 2013 after this disassembly of JT-60U torus.

Journal Articles

Development of divertor simulation research in the GAMMA 10/PDX tandem mirror

Nakashima, Yosuke*; Sakamoto, Mizuki*; Yoshikawa, Masayuki*; Oki, Kensuke*; Takeda, Hisahito*; Ichimura, Kazuya*; Hosoi, Katsuhiro*; Hirata, Mafumi*; Ichimura, Makoto*; Ikezoe, Ryuya*; et al.

Proceedings of 25th IAEA Fusion Energy Conference (FEC 2014) (CD-ROM), 8 Pages, 2014/10

Journal Articles

Feasible evaluation of neutron capture therapy for hepatocellular carcinoma using selective enhancement of boron accumulation in tumour with intra-arterial administration of boron-entrapped water-in-oil-in-water emulsion

Yanagie, Hironobu*; Kumada, Hiroaki*; Nakamura, Takemi; Higashi, Shushi*; Ikushima, Ichiro*; Morishita, Yasuyuki*; Shinohara, Atsuko*; Fujiwara, Mitsuteru*; Suzuki, Minoru*; Sakurai, Yoshinori*; et al.

Proceedings of 14th International Congress on Neutron Capture Therapy (ICNCT-14) (CD-ROM), p.157 - 160, 2010/10

Journal Articles

Recent progress in the energy recovery linac project in Japan

Sakanaka, Shogo*; Akemoto, Mitsuo*; Aoto, Tomohiro*; Arakawa, Dai*; Asaoka, Seiji*; Enomoto, Atsushi*; Fukuda, Shigeki*; Furukawa, Kazuro*; Furuya, Takaaki*; Haga, Kaiichi*; et al.

Proceedings of 1st International Particle Accelerator Conference (IPAC '10) (Internet), p.2338 - 2340, 2010/05

Future synchrotron light source using a 5-GeV energy recovery linac (ERL) is under proposal by our Japanese collaboration team, and we are conducting R&D efforts for that. We are developing high-brightness DC photocathode guns, two types of cryomodules for both injector and main superconducting (SC) linacs, and 1.3 GHz high CW-power RF sources. We are also constructing the Compact ERL (cERL) for demonstrating the recirculation of low-emittance, high-current beams using above-mentioned critical technologies.

Journal Articles

Study on the behavior of oxygen atoms in swift heavy ion irradiated CeO$$_{2}$$ by means of synchrotron radiation X-ray photoelectron spectroscopy

Iwase, Akihiro*; Ono, Hirotaka*; Ishikawa, Norito; Baba, Yuji; Hirao, Norie; Sonoda, Takeshi*; Kinoshita, Motoyasu*

Nuclear Instruments and Methods in Physics Research B, 267(6), p.969 - 972, 2009/03

 Times Cited Count:36 Percentile:91.23(Instruments & Instrumentation)

To study the effects of swift heavy ion irradiation on cerium dioxide (CeO$$_{2}$$), CeO$$_{2}$$ sintered pellets were irradiated with 200 MeV Xe ions at room temperature. For irradiated and unirradiated samples, the spectra of X-ray photoelectron spectroscopy (XPS) were measured. XPS spectra for the irradiated samples show that the valence state of Ce atoms partly changes from +4 to +3. The amount of Ce$$^{3+}$$ state was quantitatively obtained as a function of ion-fluence. The relative amount of oxygen atom displacements, which are accompanied by the decrease in Ce valence state, is 3-5%. This value is too large to be explained in terms of elastic interactions between CeO$$_{2}$$ and 200 MeV ions. The experimental result suggests the contribution of 200 MeV Xe induced electronic excitation to the displacements of oxygen atoms.

Journal Articles

Study on effects of swift heavy ion irradiation in cerium dioxide using synchrotron radiation X-ray absorption spectroscopy

Ono, Hirotaka*; Iwase, Akihiro*; Matsumura, Daiju; Nishihata, Yasuo; Mizuki, Junichiro; Ishikawa, Norito; Baba, Yuji; Hirao, Norie; Sonoda, Takeshi*; Kinoshita, Motoyasu

Nuclear Instruments and Methods in Physics Research B, 266(12-13), p.3013 - 3017, 2008/06

 Times Cited Count:57 Percentile:96.15(Instruments & Instrumentation)

Radiation damage of CeO$$_{2}$$ irradiated with 200MeV Xe is characterized by EXAFS and XPS measurement. It is found that oxygen deficiencies are created after the irradiation, and charge state of Ce is changed from +4 to +3.

Journal Articles

Chemistry in mega-gravity; Preparation of molecular-scaled graded materials from radical copolymerization

Ihara, Hirotaka; Abe, Yasuyuki*; Miyamoto, Akihiro*; Nishihara, Masamichi*; Takafuji, Makoto*; Ono, Masao; Okayasu, Satoru; Mashimo, Tsutomu

Chemistry Letters, 37(2), p.200 - 201, 2008/02

 Times Cited Count:1 Percentile:7.47(Chemistry, Multidisciplinary)

The molecular-graded structures have been realized through direct copolymerization of halogenated styrene and 2-ethylhexyl methacrylate under ultra-strong gravitational field. The graded structures were clearly confirmed by EPMA and NMR spectroscopy.

Journal Articles

Study on effects of heavy ion irradiation on CeO$$_{2}$$ by using synchrotron radiation X-ray absorption spectroscopy; As a simulation study for radiation damage in high-burnup light water reactor fuels

Ono, Hirotaka*; Matsumura, Daiju; Nishihata, Yasuo; Mizuki, Junichiro; Ishikawa, Norito; Sonoda, Takeshi*; Kinoshita, Motoyasu*; Iwase, Akihiro*

Materials Research Society Symposium Proceedings, Vol.1043, p.179 - 183, 2008/00

CeO$$_{2}$$ thin films were irradiated with 200 MeV Xe ions. Effects of the irradiation were studied by using Extended X-ray Absorption Fine Structure (EXAFS) measurement at SPring-8 synchrotron radiation facility. EXAFS spectra for the irradiated thin films near the Ce K-edge show that the coordination number for oxygen atoms around Ce atom decreases and that the Ce-O Debye-Waller factor increases by the irradiation. The atomic distance between oxygen atom and Ce atom does not vary within the accuracy of EXAFS measurement. The effect of high density electronic excitation on the structure of CeO$$_{2}$$ is discussed.

Journal Articles

ELM propagation and fluctuations characteristics in H- and L-mode SOL plasmas on JT-60U

Asakura, Nobuyuki; Ono, Noriyasu*; Kawashima, Hisato; Miyoshi, Hideaki*; Matsunaga, Go; Oyama, Naoyuki; Takamura, Shuichi*; Uesugi, Yoshihiko*; Takechi, Manabu; Nakano, Tomohide; et al.

Proceedings of 21st IAEA Fusion Energy Conference (FEC 2006) (CD-ROM), 8 Pages, 2007/03

Radial transport of the SOL plasma was recently studied in order to understand heat and particle loading to the first wall and the SOL formation mechanism. Fast propagation of the ELM plasma and fluctuation properties in H- and L-modes were determined at low-field-side (LFS) SOL using reciprocating Mach probes in JT-60U. Large and short peaks were found in ELM plasma flux, which was regularly enhanced after each ELM event. Transport dynamics of the first large ${it j$_{s}$}$ peak was determined, i.e. it propagated to near the first wall with the fast velocity of 1.3-2.5 km/s. Statistical analysis of a probability distribution function was applied to describe intermittent (non-diffusion) transport in SOL plasma fluctuations. It was found that the positive bursty events appeared in a wide SOL region, where the flow reversal of the SOL plasma was observed. Influences of the radial transport of the convective blobby plasma on the SOL formation and the flow reversal were investigated.

Journal Articles

Physics issues and simulation of the JT-60 SA divertor for large heat and particle handling

Asakura, Nobuyuki; Kawashima, Hisato; Shimizu, Katsuhiro; Sakurai, Shinji; Fujita, Takaaki; Takenaga, Hidenobu; Nakano, Tomohide; Kubo, Hirotaka; Higashijima, Satoru; Hayashi, Takao; et al.

Europhysics Conference Abstracts (CD-ROM), 31F, 4 Pages, 2007/00

Divertor design for the JT-60 SA has been progressing in order to handle large heat flux during full pulse duration of 100 s. Divertor should be suitable for single null plasma experiments with the full power injection of 41 MW. The simulation results using 2D fluid (plasma) and Monte-Carlo (neutral) code are summarized. Lower single-null divertor is designed for ITER-like plasma configuration in order to study physics concept of the ITER divertor: control of the plasma detachment. Simulation results for various divertor geometries showed that the vertical target with V-shaped corner can produce plasma detachment near the outer strike-point for medium edge plasma density. It was also demonstrated that the divertor plasma became attached to move the outer strike point above the V-corner, suggesting that recover from sever detachment can be achieved by changing the plasma location. USN divertor will be designed for high-$$beta$$ plasma experiments with the highest shaping plasma of S=6.

Journal Articles

Spectroscopic diagnostics in boundary plasmas

Nakano, Tomohide; Fujimoto, Takashi*; Goto, Motoshi*; Hatayama, Akiyoshi*; Kado, Shinichiro*; Kato, Takako*; Kimura, Mineo*; Kubo, Hirotaka; Murakami, Izumi*; Ono, Noriyasu*; et al.

Annual Report of National Institute for Fusion Science; April 2003 - March 2004, P. 414, 2003/10

no abstracts in English

Journal Articles

Advanced high-temperature ultracentrifuge apparatus for mega-gravity materials science

Mashimo, Tsutomu; Huang, X.; Osakabe, Toyotaka; Ono, Masao*; Nishihara, Masamichi*; Ihara, Hirotaka*; Sueyoshi, Masanori*; Shibasaki, Koji*; Shibasaki, Shiro*; Mori, Nobuo*

Review of Scientific Instruments, 74(1), p.160 - 163, 2003/01

 Times Cited Count:53 Percentile:89.01(Instruments & Instrumentation)

An ultracentrifuge apparatus, which could generate an ultra-strong gravitational field of even $$>$$1,000,000 (1 million) G (1G = 9.8 m/s$$^{2}$$) in a wide temperature range up to $$>$$ 500$$^{circ}$$C with high stability controls, was developed for new materials science research. The system consisted of an air turbine motor with ceramic ball bearings and dumper section, a sample rotor with an outer diameter up to 160 mm, a vacuum chamber and a heating system. The ultracentrifuge experiments using the 70 and 80 mm-diam rotors made of titanium alloy with rotational speeds of up to 170,000 rpm at temperatures of even over 200$$^{circ}$$C for 100 hours with the ripples of $$<$$ 0.05% and $$<$$ 1 degree, respectively, were successfully performed, where the maximum gravitational field at sample was $$>$$1,000,000 G, and the potential energy and sample volume were larger than those of the Kumamoto University one (Rev. Sci. Instr. 67, 3170 (1996)) by $$>$$ 1.9 and $$>$$ 4 times, respectively.

Oral presentation

Temporal evolution of electron temperature and density during ELM in JT-60 divertor plasma

Nakano, Tomohide; Asakura, Nobuyuki; Ono, Noriyasu*; Kajita, Shin*; Kawashima, Hisato; Kubo, Hirotaka; Shimizu, Katsuhiro; Fujimoto, Kayoko

no journal, , 

no abstracts in English

28 (Records 1-20 displayed on this page)