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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:97.01(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

Convergence behavior in line profile analysis using convolutional multiple whole-profile software

Kumagai, Masayoshi*; Uchida, Tomohiro*; Murasawa, Kodai*; Takamura, Masato*; Ikeda, Yoshimasa*; Suzuki, Hiroshi; Otake, Yoshie*; Hama, Takayuki*; Suzuki, Shinsuke*

Materials Research Proceedings, Vol.6, p.57 - 62, 2018/10

 Times Cited Count:0 Percentile:0.18

JAEA Reports

Annual report of Nuclear Emergency Assistance and Training Center (April 1, 2012 - March 31, 2013)

Sato, Takeshi; Muto, Shigeo; Okuno, Hiroshi; Katagiri, Hiromi; Akiyama, Kiyomitsu; Okamoto, Akiko; Koie, Masahiro; Ikeda, Takeshi; Nemotochi, Toshimasa; Saito, Toru; et al.

JAEA-Review 2013-046, 65 Pages, 2014/02

JAEA-Review-2013-046.pdf:11.18MB

When a nuclear emergency occurs in Japan, the Japan Atomic Energy Agency (JAEA) has the responsibility of providing technical support to the National government, local governments, police, fire stations and nuclear operators etc., because the JAEA has been designated as the Designated Public Institution under the Basic Act on Disaster Control Measures and the Act on Response to Armed Attack Situations, etc.. The Nuclear Emergency Assistance and Training Center (NEAT) of JAEA provides a comprehensive range of technical support activities to an Off-Site Center in case of a nuclear emergency. Specifically, NEAT gives technical advice and information, dispatches specialists as required, and supplies the National Government and local governments with emergency equipments and materials. NEAT provides various exercise and training courses concerning nuclear disaster prevention to those personnel taking an active part in emergency response organizations at normal times. The tasks of NEAT, with its past experiences as a designated public institution including the responses to TEPCO's Fukushima Accident, have been shifted to technical supports to the national government for strengthening its abilities to emergency responses; the NEAT therefore focused on maintenance and operation of its functions, and strengthening its response abilities in cooperation with the national government. This annual report summarized these activities of JAEA/NEAT in the fiscal year 2012.

JAEA Reports

Annual report of Nuclear Emergency Assistance and Training Center (April 1, 2011 - March 31, 2012)

Katagiri, Hiromi; Okuno, Hiroshi; Okamoto, Akiko; Ikeda, Takeshi; Tamura, Kenichi; Nagakura, Tomohiro; Nakanishi, Chika; Yamamoto, Kazuya; Abe, Minako; Sato, Sohei; et al.

JAEA-Review 2012-033, 70 Pages, 2012/08

JAEA-Review-2012-033.pdf:6.38MB

When a nuclear emergency occurs in Japan, JAEA has the responsibility of providing technical support to the National government, local governments, etc., by the Basic Law on Emergency Preparedness and the Basic Plan for Disaster Countermeasures. NEAT of JAEA gives technical advice and information, dispatch specialists as required, supplies with the National Government and local governments emergency equipment and materials. NEAT provides various lectures and training courses concerning nuclear disaster prevention for emergency response organizations at normal time. Concerning the assistance to the Accident of Fukushima No.1 Nuclear Power Station caused by the Great East Japan Earthquake on 11 March, 2011, JAEA assisted activities including environmental radiation monitoring, environmental radioactivity analyses, resident public consulting etc., with its the utmost effort. This annual report summarized these activities of NEAT in the fiscal year 2011.

JAEA Reports

Annual report of Nuclear Emergency Assistance and Training Center (April 1, 2010 - March 31, 2011)

Katagiri, Hiromi; Okuno, Hiroshi; Sawahata, Masayoshi; Ikeda, Takeshi; Sato, Sohei; Terakado, Naoya; Nagakura, Tomohiro; Nakanishi, Chika; Fukumoto, Masahiro; Yamamoto, Kazuya; et al.

JAEA-Review 2011-037, 66 Pages, 2011/12

JAEA-Review-2011-037.pdf:4.52MB

When a Nuclear emergency occurs, Nuclear Emergency Assistance & Training Center (NEAT) of JAEA gives technical advice and information, dispatch specialists as required, supplies emergency equipment and materials to the National Government and local governments. NEAT provides various lectures and training courses concerning nuclear disaster prevention for those personnel taking an active part in emergency response organizations at normal time. NEAT also researches on nuclear disaster prevention and cooperates with international organizations. Concerning about the assistance to the Accident of Fukushima No.1 Nuclear Power Station caused by the Great East Japan Earthquake at 11 March, 2011, JAEA assisted activities including environmental radiation monitoring, environmental radioactivity analyses, resident public consulting etc., with its full scale effort. NEAT served as the center of these supporting activities of JAEA.

Journal Articles

Site dependent hardening of the lanthanum metal lattice by hydrogen absorption

Machida, Akihiko; Watanuki, Tetsu; Omura, Ayako*; Ikeda, Tomohiro*; Aoki, Katsutoshi; Nakano, Satoshi*; Takemura, Kenichi*

Solid State Communications, 151(5), p.341 - 345, 2011/03

 Times Cited Count:10 Percentile:42.24(Physics, Condensed Matter)

The compressibility of lanthanum (La) metal and its hydrides were measured at room temperature by high pressure synchrotron X-ray diffraction. La metal pressurized in a hydrogen medium forms a hydride with an fcc metal lattice, which likely contains hydrogen at a concentration close to 3.0. Equations of state have been determined by helium compression experiments for LaH$$_2$$ with tetrahedral interstitial sites fully occupied with hydrogen atoms and for LaH$$_{2.46}$$ with octahedral interstitial sites partially occupied with hydrogen atoms and tetrahedral sites fully occupied. Both hydrides possess fcc metal lattices. These values are three times larger than that of La metal and are very close to each other despite the difference in hydrogen occupation states. The hardening of the metal lattice by hydrogenation is attributed predominantly to hydrogen-metal interactions at the tetrahedral sites and is most pronounced for La, which has the largest ionic radius among rare-earth metals.

JAEA Reports

Annual report of Nuclear Emergency Assistance and Training Center (April 1, 2009 - March 31, 2010)

Kanamori, Masashi; Shirakawa, Yusuke; Yamashita, Toshiyuki; Okuno, Hiroshi; Terunuma, Hiroshi; Ikeda, Takeshi; Sato, Sohei; Terakado, Naoya; Nagakura, Tomohiro; Fukumoto, Masahiro; et al.

JAEA-Review 2010-037, 60 Pages, 2010/09

JAEA-Review-2010-037.pdf:3.11MB

When a nuclear emergency occurs in Japan, the Japan Atomic Energy Agency (JAEA) provides technical support to the National government, local governments, police, fire station and license holder etc. They are designated public organizations conforming to the basic law on emergency preparedness and the basic plan for disaster countermeasures. The Nuclear Emergency Assistance & Training Center (NEAT) of JAEA provides a comprehensive range of technical support activities to an off-site center in case of a nuclear emergency. Specifically, NEAT gives technical advice and information, provides for the dispatch of specialist as required, supplies emergency equipments and materials to the national government and municipal office. NEAT provide various lectures and training course concerning nuclear disaster prevention for those personnel taking an active part in emergency response organizations at normal time. And NEAT researches on nuclear disaster prevention and also cooperate with international organizations. This annual report summarized the activities of JAEA/NEAT in the fiscal year 2009.

JAEA Reports

Annual report of Nuclear Emergency Assistance and Training Center (April 1, 2008 - March 31, 2009)

Kanamori, Masashi; Hashimoto, Kazuichiro; Terunuma, Hiroshi; Ikeda, Takeshi; Omura, Akiko; Terakado, Naoya; Nagakura, Tomohiro; Fukumoto, Masahiro; Watanabe, Fumitaka; Yamamoto, Kazuya; et al.

JAEA-Review 2009-023, 61 Pages, 2009/09

JAEA-Review-2009-023.pdf:8.49MB

When a nuclear emergency occurs in Japan, the Japan Atomic Energy Agency (JAEA) provides technical support to the National government, local governments, police, fire station and license holder etc. They are Designated Public Organizations conforming to the Basic Law on Emergency Preparedness and the Basic Plan for Disaster Countermeasures. The Nuclear Emergency Assistance and Training Center (NEAT) of JAEA provides a comprehensive range of technical support activities to an Off-Site Center in case of a nuclear emergency. Specifically, NEAT gives technical advice and information, provides for the dispatch of specialist as required, supplies emergency equipments and materials to the Joint Council of Nuclear Disaster Countermeasures, which meets at the Off-Site Center. NEAT provide various lectures and training course concerning nuclear disaster prevention for those personnel taking an active part in emergency response organizations at normal time. And NEAT researches on nuclear disaster prevention and also cooperate with international organizations. This annual report summarized the activities of JAEA/NEAT in the fiscal year 2008.

Journal Articles

Extended steady-state and high-beta regimes of net-current free heliotron plasmas in the Large Helical Device

Motojima, Osamu*; Yamada, Hiroshi*; Komori, Akio*; Oyabu, Nobuyoshi*; Muto, Takashi*; Kaneko, Osamu*; Kawahata, Kazuo*; Mito, Toshiyuki*; Ida, Katsumi*; Imagawa, Shinsaku*; et al.

Nuclear Fusion, 47(10), p.S668 - S676, 2007/10

 Times Cited Count:34 Percentile:73.89(Physics, Fluids & Plasmas)

The performance of net-current free heliotron plasmas has been developed by findings of innovative operational scenarios in conjunction with an upgrade of the heating power and the pumping/fuelling capability in the Large Helical Device (LHD). Consequently, the operational regime has been extended, in particular, with regard to high density, long pulse length and high beta. Diversified studies in LHD have elucidated the advantages of net-current free heliotron plasmas. In particular, an internal diffusion barrier (IDB) by a combination of efficient pumping of the local island divertor function and core fuelling by pellet injection has realized a super dense core as high as 5$$times$$10$$^{20}$$ m$$^{-3}$$, which stimulates an attractive super dense core reactor. Achievements of a volume averaged beta of 4.5% and a discharge duration of 54 min with a total input energy of 1.6 GJ (490 kW on average) are also highlighted. The progress of LHD experiments in these two years is overviewed by highlighting IDB, high-beta and long pulse.

Journal Articles

Development of a single-crystal X-ray diffraction system for hydrostatic-pressure and low-temperature structural measurement and its application to the phase study of quasicrystals

Watanuki, Tetsu; Machida, Akihiko; Ikeda, Tomohiro*; Omura, Ayako*; Kaneko, Hiroshi; Aoki, Katsutoshi; Sato, Taku*; Tsai, A. P.*

Philosophical Magazine, 87(18-21), p.2905 - 2911, 2007/06

 Times Cited Count:46 Percentile:87.31(Materials Science, Multidisciplinary)

We have constructed a single-crystal synchrotron X-ray diffraction system to precisely study the structure under hydrostatic pressure conditions at low temperatures and applied it to a study on the phase transition phenomena of a Cd-Yb periodic approximant and a Cd-Yb quasicrystal. Four phases were newly observed for the 1/1 approximant crystal in a $$P-T$$ span up to 5.2 GPa and down to 10 K. The innermost part of the atomic clusters of Cd$$_{4}$$ tetrahedra exhibited various orientational ordering sensitively depending on pressure and temperature. High pressure diffraction measurements using a highly parallel synchrotron X-ray beam and a hydrostatically compressed single crystal enabled us to detect the weak diffractions due to the subtle structural changes.

Journal Articles

Extended steady-state and high-beta regimes of net-current free heliotron plasmas in the large helical device

Motojima, Osamu*; Yamada, Hiroshi*; Komori, Akio*; Oyabu, Nobuyoshi*; Kaneko, Osamu*; Kawahata, Kazuo*; Mito, Toshiyuki*; Muto, Takashi*; Ida, Katsumi*; Imagawa, Shinsaku*; et al.

Proceedings of 21st IAEA Fusion Energy Conference (FEC 2006) (CD-ROM), 12 Pages, 2007/03

The performance of net-current free Heliotron plasmas has been developed by findings of innovative operational scenarios in conjunction with an upgrade of the heating power and the pumping/fueling capability in the Large Helical Device (LHD). Consequently, the operational regime has been extended, in particular, with regard to high density, long pulse length and high beta. Diversified studies in LHD have elucidated the advantages of net-current free heliotron plasmas. In particular, an Internal Diffusion Barrier (IDB) by combination of efficient pumping of the local island divertor function and core fueling by pellet injection has realized a super dense core as high as 5$$times$$10$$^{20}$$m$$^{-3}$$, which stimulates an attractive super dense core reactor. Achievements of a volume averaged beta of 4.5 % and a discharge duration of 54-min. with a total input energy of 1.6 GJ (490 kW in average) are also highlighted. The progress of LHD experiments in these two years is overviewed with highlighting IDB, high $$beta$$ and long pulse.

Journal Articles

Pressure-induced phase transitions in the Cd-Yb periodic approximant to a quasicrystal

Watanuki, Tetsu; Machida, Akihiko; Ikeda, Tomohiro*; Aoki, Katsutoshi; Kaneko, Hiroshi; Shobu, Takahisa; Sato, Taku*; Tsai, A. P.*

Physical Review Letters, 96(10), p.105702_1 - 105702_4, 2006/03

 Times Cited Count:30 Percentile:77.09(Physics, Multidisciplinary)

The phase study of a Cd-Yb 1/1 approximant crystal over a wide pressure and temperature range is crucial for the comparison study between periodic and quasi-periodic crystals. The Cd4 tetrahedra, the most inner part of the atomic clusters, exhibited various structural ordering in the orientation sensitive to pressure and temperature. Five ordered phases appeared in a P-T span up to 5.2 GPa and down to 10K. The propagation direction of ordering alternated from [110] to $$<$$111$$>$$ at about 1.0 GPa and again to [110] at 3.5-4.3 GPa. The primarily ordered phases that appeared by cooling to 210-250K between 1-5.2 GPa further transformed to finely ordered ones at 120-155K. In addition to the original short-range type interaction, a long-range type interaction was likely developed under pressure to lead to the primary ordering of Cd4 tetrahedra. Coexistence of the two different type interactions is responsible for the complicated phase behavior.

Journal Articles

A Demonstration study of focusing geometry SANS using a magnetic neutron lens

Oku, Takayuki; Suzuki, Junichi; Sasao, Hajime*; Yamada, Satoru; Furusaka, Michihiro*; Adachi, Tomohiro*; Shinohara, Takenao*; Ikeda, Kazuaki*; Shimizu, Hirohiko

Physica B; Condensed Matter, 356(1-4), p.126 - 130, 2005/02

 Times Cited Count:11 Percentile:45.57(Physics, Condensed Matter)

We have developed a magnetic neutron lens (MNL) based on a sextupole magnet. A neutron beam, which is incident to the sextupole magnet, either converges or diverges depending on the neutron spin state. Small-angle neutron scattering in focusing geometry (FSANS) was proposed to improve the q-resolution and/or measuring efficiency. The MNL is considered to be the most suitable focusing device for FSANS experiments using a polarized neutron beam, since it focuses the polarized neutron beam free from neutron attenuation and scattering by substances. Recently, we have developed the MNLs with sufficiently large apertures and strong focusing power for FSANS experiments. In this study, we evaluate the focusing property of the MNLs for the polarized neutron beam, and performed FSANS experiments using the MNL. The obtained results are discussed.

Journal Articles

Feasibility study on application of a magnetic neutron lens to SANS experiments

Oku, Takayuki; Suzuki, Junichi; Sasao, Hajime*; Adachi, Tomohiro*; Shinohara, Takenao*; Ikeda, Kazuaki*; Morishima, Takahiro*; Sakai, Kenji*; Kiyanagi, Yoshiaki*; Furusaka, Michihiro*; et al.

Nuclear Instruments and Methods in Physics Research A, 529(1-3), p.116 - 119, 2004/08

 Times Cited Count:20 Percentile:77.97(Instruments & Instrumentation)

As a neutron has a magnetic dipole moment, it is accelerated in a magnetic field gradient. Thus, we can control a neutron trajectory free from neutron beam attenuation and scattering using the magnetic field gradient. A sextupole magnetic field functions as a neutron focusing and defocusing lens depending on the neutron spin state. The neutron focusing effect was experimentally verified using a 6-piece permanent sextupole magnet. For the application in practical neutron scattering experiments, a sextupole magnet with a sufficiently large aperture accompanied with strong focusing power is demanded. Recently, a superconducting sextupole magnet, a Halbach-type permanent sextupole magnet and a sextupole pulse electro-magnet have been developed in a project of the development and application of neutron optics. These magnets will be dedicated to practical uses in neutron scattering experiments. In this paper, current status of the development of the magnetic neutron lenses is reported, and their application in the neutron scattering experiments is discussed.

Journal Articles

Development of a spin flipper for an application of a neutron magnetic device

Oku, Takayuki*; Sakai, Kenji*; Adachi, Tomohiro*; Ikeda, Kazuaki*; Shimizu, Hirohiko*; Maruyama, Ryuji*; Hino, Masahiro*; Tasaki, Seiji*; Kiyanagi, Yoshiaki*; Kamiyama, Takashi*; et al.

Physica B; Condensed Matter, 335(1-4), p.226 - 229, 2003/07

 Times Cited Count:7 Percentile:39.47(Physics, Condensed Matter)

no abstracts in English

Oral presentation

Metallic particle formation by proton irradiation in liquid

Kobayashi, Tomohiro*; Ikeda, Tokihiro*; Ogiwara, Kiyoshi*; Yamazaki, Yasunori*; Hakoda, Teruyuki; Yamaki, Tetsuya

no journal, , 

Water solution containing 1 mmol/L PtCl$$_{4}$$$$^{2-}$$ ions and 10v% ethanol was irradiated with 3-MeV proton beams. After irradiation, metal platinum particles were produced and suspended in the solution. These particles were deposited on the surface of glassy carbon disks which were placed in the soution.

Oral presentation

Disordered materials studies with high intensity total diffractometer at J-PARC

Suzuya, Kentaro; Oshita, Hidetoshi*; Otomo, Toshiya*; Ikeda, Kazutaka*; Seya, Tomohiro*; Kaneko, Naokatsu*; Fujisaki, Fumika*

no journal, , 

NOVA has almost 900 3-helium gas detectors for neutron diffraction measurements. Two Gas Electron Multiplier (GEMs) are installed as an incident-neutron and a transmission beam monitors. The performance of NOVA has been confirmed by several samples: structural analysis of crystalline and amorphous samples are demonstrated, the instrument background is low enough to measure S(Q) with the order of several ten mg for an hour. Typical S(Q) of silica glass (cylindrical rod, 20 mm long, and 7 mm diameter) is obtained up to 15 (1/${AA}$) for 1 sec and up to 35 (1/${AA}$) for 20 sec. These results show that NOVA is a powerful instrument for in situ dynamic investigation of rapid structural transformation in supercooled liquids and in hydrogen storage materials. Some of recent results of disordered materials on NOVA will be presented.

Oral presentation

Depositional sequence of the Post-LGM incised-valley fill controlled by seismic crustal deformation and large-scale lahars; An Example of SKM core obtained from the Sukumo coastal lowland along the Nankai Trough, Japan

Nanayama, Futoshi*; Yamaguchi, Tatsuhiko*; Nakanishi, Toshimichi; Tsuji, Tomohiro*; Ikeda, Michiharu*; Kondo, Yasuo*; Miwa, Michiko*; Sugiyama, Shinji*; Kimura, Kazunari*

no journal, , 

The characteristics of the post-LGM incised valley fills and the depositional sequence were examined the SKM core collected in the Sukumo coastal lowland, where is expected to huge seismic subsidence due to the Nankai Trough great earthquakes. Our sedimentological, radiocarbon dating and paleoenvironmental results are as bellows. Sediments of the SKM core clearly show a succession influenced by post-glacial sea level change. The Matsuda River incised valley was formed in LGM and filled by fluvial sand and gravels in late Pleistocene. After the postglacial transgression, sea level reached -30 m (a.s.l.) at 9.8 ka and the incised valley changed to an estuary environment. The sea level continued to rise and it became an inner bay mud bottom environment, and reaching a maximum water depth was at 7.5 ka. The 7.3 ka Kikai caldera eruption in southern Kyushu caused heavy K-Ah ash fall in southwestern Shikoku, and then large-scale lahars frequently occurred immediately after the ash fall because of the vicinity of volcanic source. After ash fall, the K-Ah secondary sediments rapidly deposited on the inner bay environment and caused forced regression. After 7.0 ka, the growth of the delta became active ahead of the other regions, which may be due to the large K-Ah ash fall. At 5 ka, the sea level reached + 2.5 m (a.s.l.) estimated by the Sukumo midden and this altitude is recognized as the Holocene marine limit in this area. The information on relative sea level change during the past 10000 years has revealed that the Sukumo Bay area has not subsided due to seismic crustal deformation.

Oral presentation

Middle Holocene changes in relative sea-level on western Shikoku Island, Japan

Yamaguchi, Tatsuhiko*; Tsuji, Tomohiro*; Nanayama, Futoshi*; Nakanishi, Toshimichi; Ikeda, Michiharu*; Kondo, Yasuo*; Miwa, Michiko*; Hamada, Yohei*

no journal, , 

Shikoku Island is situated 150 km northwest of the Nankai trough that has developed in response to the convergence of the subducting Philippine Sea Plate and overriding Eurasian Plate. This tectonism causes deformation of the island, megathrust earthquakes, and tsunamis. Shikoku Island experiences coseismic and interseismic deformation. The middle Holocene tectonics of the island are still poorly understood. Relative sea-level (RSL) changes indicated by coastal sediments potentially record seismic uplift and subsidence. To infer RSL changes between 8 and 4 cal. kyr BP, we studied Holocene ostracode assemblages from the SKM drill core in Sukumo, southwest Shikoku Island (Tsuji et al., 2018, JpGU, MIS11-P19), and from six cores in the northern part of the island (Yasuhara et al., 2005, Palaeo3; Yasuhara and Seto, 2006, Paleontol. Res. 10). To estimate paleo-water depth and RSL, we employed the ostracode assemblages and modern analog technique. The SKM core is composed of conglomerate, ash, and mud chiefly. Its geological age was examined, using the $$^{14}$$C dating method (Nakanishi et al., 2019, Radiocarbon). The differences in RSL were identified across the island, possibly due to convergence of the Philippine Sea Plate.

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