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Journal Articles

Quantum critical behavior of the hyperkagome magnet Mn$$_3$$CoSi

Yamauchi, Hiroki; Sari, D. P.*; Yasui, Yukio*; Sakakura, Terutoshi*; Kimura, Hiroyuki*; Nakao, Akiko*; Ohara, Takashi; Honda, Takashi*; Kodama, Katsuaki; Igawa, Naoki; et al.

Physical Review Research (Internet), 6(1), p.013144_1 - 013144_9, 2024/02

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

High-temperature short-range order in Mn$$_3$$RhSi

Yamauchi, Hiroki; Sari, D. P.*; Watanabe, Isao*; Yasui, Yukio*; Chang, L.-J.*; Kondo, Keietsu; Ito, Takashi; Ishikado, Motoyuki*; Hagihara, Masato*; Frontzek, M. D.*; et al.

Communications Materials (Internet), 1, p.43_1 - 43_6, 2020/07

High-temperature short-range order is discovered up to 720 K in Mn$$_3$$RhSi by complementary use of neutron scattering and muon spin relaxation measurements.

Journal Articles

Experimental determination of the photooxidation of aqueous I$$^{-}$$ as a source of atmospheric I$$_{2}$$

Watanabe, Kosuke*; Matsuda, Shohei; Cuevas, C. A.*; Saiz-Lopez, A.*; Yabushita, Akihiro*; Nakano, Yukio*

ACS Earth and Space Chemistry (Internet), 3(4), p.669 - 679, 2019/04

 Times Cited Count:7 Percentile:44.3(Chemistry, Multidisciplinary)

The photooxidation of aqueous iodide ions (I$$^{-}$$$$_{(aq)}$$) at sea surface results in the emission of gaseous iodine molecules (I$$_{2}$$$$_{(g)}$$) into the atmosphere. It plays a certain role in the transport of iodine from ocean to the atmosphere in the natural cycle of iodine. In this study, we determined the photooxidation parameters, the molar absorption coefficient ($$varepsilon$$$$_{iodide}$$($$lambda$$)) and the photooxidative quantum yields ($$Phi$$$$_{iodide}$$($$lambda$$)) of I$$^{-}$$$$_{(aq)}$$, in the range of 290-500 nm. Through the investigation of the influence of pH and dissolved oxygen (DO) on $$Phi$$$$_{iodide}$$($$lambda$$), the subsequent emission rates of I$$_{2}$$$$_{(g)}$$ following the photooxidation of I$$^{-}$$$$_{(aq)}$$ in deionized water solution (pH 5.6, DO 7.8 mg L$$^{-1}$$) and artificial seawater solution (pH 8.0, DO 7.0 mg L$$^{-1}$$) were estimated. A global chemistry-climate model employed herein to assess the I$$_{2}$$$$_{(g)}$$ ocean emission on a global scale indicated that the photooxidation of I$$^{-}$$$$_{(aq)}$$ by solar light can enhance the atmospheric iodine budget by up to $$sim$$8% over some oceanic regions.

Journal Articles

The Surface composition of asteroid 162173 Ryugu from Hayabusa2 near-infrared spectroscopy

Kitazato, Kohei*; Milliken, R. E.*; Iwata, Takahiro*; Abe, Masanao*; Otake, Makiko*; Matsuura, Shuji*; Arai, Takehiko*; Nakauchi, Yusuke*; Nakamura, Tomoki*; Matsuoka, Moe*; et al.

Science, 364(6437), p.272 - 275, 2019/04

 Times Cited Count:233 Percentile:99.74(Multidisciplinary Sciences)

The near-Earth asteroid 162173 Ryugu, the target of Hayabusa2 sample return mission, is believed to be a primitive carbonaceous object. The Near Infrared Spectrometer (NIRS3) on Hayabusa2 acquired reflectance spectra of Ryugu's surface to provide direct measurements of the surface composition and geological context for the returned samples. A weak, narrow absorption feature centered at 2.72 micron was detected across the entire observed surface, indicating that hydroxyl (OH)-bearing minerals are ubiquitous there. The intensity of the OH feature and low albedo are similar to thermally- and/or shock-metamorphosed carbonaceous chondrite meteorites. There are few variations in the OH-band position, consistent with Ryugu being a compositionally homogeneous rubble-pile object generated from impact fragments of an undifferentiated aqueously altered parent body.

Journal Articles

The Catalytic mechanism of decarboxylative hydroxylation of salicylate hydroxylase revealed by crystal structure analysis at 2.5${AA}$ resolution

Uemura, Takuya*; Kita, Akiko*; Watanabe, Yoshihiko*; Adachi, Motoyasu; Kuroki, Ryota; Morimoto, Yukio*

Biochemical and Biophysical Research Communications, 469(2), p.158 - 163, 2016/01

 Times Cited Count:15 Percentile:50.83(Biochemistry & Molecular Biology)

Journal Articles

Effect of water radiolysis on surface oxide film formed on SUS316L in $$gamma$$-ray irradiated high temperature water

Yamamoto, Masahiro; Kato, Chiaki; Sato, Tomonori; Nakahara, Yukio; Tsukada, Takashi; Watanabe, Atsushi*; Fuse, Motomasa*

Proceedings of Annual Congress of the European Federation of Corrosion (EUROCORR 2013) (CD-ROM), 5 Pages, 2013/09

Major corrosion problems of light water reactor (LWR) which are represented by stress corrosion cracking are affected by dissolved oxygen (DO) concentration in feed water. Many corrosion tests were conducted with the parameter of DO values. Oxygen source of an actual LWR is radiolysis of cooling water and also H$$_{2}$$O$$_{2}$$ is generated. The effect of these species created by water radiolysis to corrosion of structural material was not sufficiently examined. $$gamma$$-ray irradiated experiments were conducted in high temperature water condition using type 316L stainless steels with crevice. The calculation of radiolysis products was not estimated by the effect of radiolysis products. From these results, much complicated reaction seemed to occur at the $$gamma$$-ray irradiated crevice portion.

JAEA Reports

Information basis for developing comprehensive waste management system; US-Japan Joint Nuclear Energy Action Plan Waste Management Working Group Phase I report (Joint research)

Yui, Mikazu; Ishikawa, Hirohisa; Watanabe, Atsuo*; Yoshino, Kyoji*; Umeki, Hiroyuki; Hioki, Kazumasa; Naito, Morimasa; Seo, Toshihiro; Makino, Hitoshi; Oda, Chie; et al.

JAEA-Research 2010-015, 106 Pages, 2010/05

JAEA-Research-2010-015.pdf:13.58MB

This report summarizes the activity of Phase I of Waste Management Working Group of the United States - Japan Joint Nuclear Energy Action Plan started in 2007. The working group focused on consolidation of the existing technical basis between the U.S. and Japan and the joint development of a plan for future collaborative activities. Firstly, the political/regulatory frameworks related to nuclear fuel cycles in both countries were reviewed. The various advanced fuel cycle scenarios in both countries were surveyed and summarized. Secondly, the waste management/disposal system optimization was discussed. Repository system concepts for the various classifications of nuclear waste were reviewed and summarized, then disposal system optimization processes and techniques were reviewed, and factors to consider in future repository design optimization activities were also discussed. Finally the potential collaboration areas and activities related to the optimization problem were extracted.

Journal Articles

Effects of $$gamma$$-ray irradiation and crevice-like shape on the corrosion of type 316L stainless steel in high-temperature water

Nakahara, Yukio; Kato, Chiaki; Yamamoto, Masahiro; Watanabe, Atsushi*; Fuse, Motomasa*

Proceedings of Symposium on Water Chemistry and Corrosion in Nuclear Power Plants in Asia 2009 (CD-ROM), p.226 - 231, 2009/10

The irradiation effect to high-temperature water in nuclear power plant has been regarded as one of important issues for preventing corrosion and stress corrosion cracking of plant materials. However, the effects of surface reaction and configurations of material on irradiated high-temperature water chemistry have been studied little because of the difficulty of measuring the environment. In this work, we have done a series of corrosion tests of Type 316L stainless steel in high-temperature water in order to estimate the effects of $$gamma$$-ray irradiation and crevice-like shape on the water chemistry. Test specimens immersed in high-temperature water of 288 $$^{circ}$$C were $$gamma$$-ray irradiated for 500 hours. The absorbed dose rate of $$gamma$$-ray irradiation was estimated to be 30 kGy h$$^{-1}$$. The dimensions of the disk-like specimens were 16 mm in diameter by 0.5 mm in thickness. The surfaces of the specimens were mechanically finished with #800 emery paper. Sets of two specimens attached closely in order to simulate a crevice-like environment were also immersed. The surfaces of the specimens were analyzed using SEM, TEM, and laser Raman spectrometer. The results of surface analyses indicated that $$gamma$$-ray irradiation enhanced the precipitation of iron oxide on the surface and the thickness of inner oxide layer became thicker by $$gamma$$-ray irradiation. $$gamma$$-ray irradiation also changed the morphology of oxide on the surface faced to the crevice-like environment.

Journal Articles

Analysis of neutronic experiment on a simulated mercury spallation neutron target assembly bombarded by Giga-electron-Volt protons

Maekawa, Fujio; Meigo, Shinichiro; Kasugai, Yoshimi; Takada, Hiroshi; Ino, Takashi*; Sato, Setsuo*; Jerde, E.*; Glasgow, D.*; Niita, Koji*; Nakashima, Hiroshi; et al.

Nuclear Science and Engineering, 150(1), p.99 - 108, 2005/05

 Times Cited Count:6 Percentile:40.53(Nuclear Science & Technology)

A neutronic benchmark experiment on a simulated spallation neutron target assembly with 1.94, 12 and 24 GeV proton beams conducted by using the AGS accelerator at BNL/US was analyzed to investigate validity of neutronics calculations on proton accelerator driven spallation neutron sources. Monte Carlo particle transport calculation codes NMTC/JAM, MCNPX and MCNP-4A with associated cross section data in JENDL and LA-150 were used for the analysis. As a result, although the overall energy range was encompassed from GeV to meV, i.e., more than 12 orders of magnitude, calculated fast and thermal neutron fluxes agreed approximately within $$pm$$ 40 % with the experiments. Accordingly, it was concluded that neutronics calculations with these codes and cross section data were adequate for estimating nuclear properties in spallation neutron sources.

Journal Articles

Actively-cooled plasma electrode for long pulse operations in a cesium-seeded negative ion source

Fujiwara, Yukio; Watanabe, Kazuhiro; Okumura, Yoshikazu; Trainham, R.*; Jacquot, C.*

Review of Scientific Instruments, 76(1), p.013501_1 - 013501_5, 2005/01

 Times Cited Count:0 Percentile:0.01(Instruments & Instrumentation)

A new actively-cooled plasma electrode has been developed for long pulse operation in a cesium-seeded negative ion source. To keep the electrode temperature at about 300 $$^{circ}$$C, which is optimum range of temperature to enhance cesium effects, the electrode cooling structure has been designed using three-dimensional numerical simulation assuming that the heat flux from the source plasma was 15 W/cm$$^{2}$$. Water cooling tubes were brazed to the plasma electrode substrate with spacers made of stainless steel which acts as a thermal resistance. The fabricated plasma electrode has been tested in a cesium-seeded volume negative ion source called Kamaboko source. The temperature of the electrode reached 280 $$^{circ}$$C for the arc power of 41 kW, which is operating condition required for producing D- beams with current densities exceeding 20 mA/cm$$^{2}$$. It was demonstrated that the actively-cooled plasma electrode is applicable to long pulse operations, meeting the temperature requirement for optimizing the surface-production process of negative ions in the cesium seeded ion source.

JAEA Reports

Annual report on the services for chemical analysis and scientific glassblowing in the fiscal year 2001 and 2002

Ito, Mitsuo; Obara, Kazuhiro; Toida, Yukio*; Suzuki, Daisuke; Gunji, Katsubumi*; Watanabe, Kazuo

JAERI-Review 2004-007, 65 Pages, 2004/03

JAERI-Review-2004-007.pdf:5.53MB

no abstracts in English

Journal Articles

Nuclear science and engineering expected in high-intensity Proton Accelerator facility (J-PARC)

Kiyanagi, Yoshiaki*; Nagamiya, Shoji*; Oyama, Yukio; Ikeda, Yujiro; Oigawa, Hiroyuki; Igashira, Masayuki*; Baba, Mamoru*; Iwasaki, Tomohiko*; Watanabe, Yukinobu*; Ishibashi, Kenji*

Nihon Genshiryoku Gakkai-Shi, 46(3), p.173 - 197, 2004/03

no abstracts in English

Journal Articles

Current status of the AGS spallation target experiment

Nakashima, Hiroshi; Takada, Hiroshi; Kasugai, Yoshimi; Meigo, Shinichiro; Maekawa, Fujio; Kai, Tetsuya; Konno, Chikara; Ikeda, Yujiro; Oyama, Yukio; Watanabe, Noboru; et al.

Proceedings of 6th Meeting of the Task Force on Shielding Aspects of Accelerators, Targets and Irradiation Facilities (SATIF-6), (OECD/NEA No.3828), p.27 - 36, 2004/00

no abstracts in English

Journal Articles

Energetic protons from a few-micron metallic foil evaporated by an intense laser pulse

Matsukado, Koji*; Esirkepov, T. Z.; Kinoshita, Kenichi*; Daido, Hiroyuki; Utsumi, Takayuki*; Li, Z.*; Fukumi, Atsushi*; Hayashi, Yukio; Orimo, Satoshi; Nishiuchi, Mamiko; et al.

Physical Review Letters, 91(21), p.215001_1 - 215001_4, 2003/11

 Times Cited Count:136 Percentile:95.28(Physics, Multidisciplinary)

no abstracts in English

Journal Articles

Present status and prospect of microbeams at TIARA

Watanabe, Hiroshi; Sudo, Yukio

Nuclear Instruments and Methods in Physics Research B, 210, p.1 - 5, 2003/09

 Times Cited Count:4 Percentile:33.72(Instruments & Instrumentation)

no abstracts in English

Journal Articles

Research activities on neutronics under ASTE collaboration at AGS/BNL

Nakashima, Hiroshi; Takada, Hiroshi; Kasugai, Yoshimi; Meigo, Shinichiro; Maekawa, Fujio; Kai, Tetsuya; Konno, Chikara; Ikeda, Yujiro; Oyama, Yukio; Watanabe, Noboru; et al.

Journal of Nuclear Science and Technology, 39(Suppl.2), p.1155 - 1160, 2002/08

no abstracts in English

Journal Articles

Symmetry breaking in the metal-insulator transition of BaVS$$_{3}$$

Inami, Toshiya; Owada, Kenji; Kimura, Hiroyuki*; Watanabe, Masashi*; Noda, Yukio*; Nakamura, Hiroyuki*; Yamasaki, Tomoaki*; Shiga, Masayuki*; Ikeda, Naoshi*; Murakami, Yoichi

Physical Review B, 66(7), p.073108_1 - 073108_4, 2002/08

 Times Cited Count:43 Percentile:84.34(Materials Science, Multidisciplinary)

It has been believed for a long time that the metal-to-insulator (MI) transition of BaVS$$_{3}$$ is not accompanied by any spatial order of spin and lattice. We have carried out x-ray diffraction measurements of BaVS$$_{3}$$ single crystals using laboratory x-ray source as well as synchrotron radiation, and found that superlatiice reflections which double the lattice constant c exist below the transition temperature. The most porbable space group at the low-temperature insulator phase contains two in equivalent vanadium sites and thus a charge disproportionation of the vnadium ions is considered as the main cause of the MI transition.

Journal Articles

Development of re-irradiation techniques using JMTR

Matsui, Yoshinori; Ide, Hiroshi; Itabashi, Yukio; Kikuchi, Taiji; Ishikawa, Kazuyoshi; Abe, Shinichi; Inoue, Shuichi; Shimizu, Michio; Iwamatsu, Shigemi; Watanabe, Naoki*; et al.

UTNL-R-0416, p.5_1 - 5_10, 2002/03

no abstracts in English

Journal Articles

Spatial uniformity of negative ion production in volume negative ion source

Morishita, Takatoshi; Miyamoto, Kenji*; Fujiwara, Yukio*; Hanada, Masaya; Kitagawa, Tadashi*; Kashiwagi, Mieko; Okumura, Yoshikazu; Watanabe, Kazuhiro

Review of Scientific Instruments, 73(2), p.1064 - 1066, 2002/02

 Times Cited Count:2 Percentile:18.97(Instruments & Instrumentation)

no abstracts in English

76 (Records 1-20 displayed on this page)