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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:44 Percentile:96.99(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 C, similar to the surface. In contrast, thermophysical modeling indicates that radiative heating does not increase the temperature above 200 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.
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:262 Percentile:99.73(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.
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:20 Percentile:84.82(Materials Science, Multidisciplinary)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
Nagao, Keisuke*; Okazaki, Ryuji*; Nakamura, Tomoki*; Miura, Yayoi*; Osawa, Takahito; Bajo, Kenichi*; Matsuda, Shintaro*; Ebihara, Mitsuru*; Ireland, T.*; Kitajima, Fumio*; et al.
Science, 333(6046), p.1128 - 1131, 2011/08
Times Cited Count:131 Percentile:95.14(Multidisciplinary Sciences)A steroid surface materials record regolith processes and a history of cosmic-ray irradiation. Noble gas isotopes in three rocky grains from Itokawa have been determined. High concentrations of solar He, Ne, and Ar, as high as those in lunar soils, are released at variable temperatures from each sample. The isotopic compositions are essentially identical to those of solar wind but distinguishable in He relative abundance. These noble gas characteristics can be explained by repeated implantation and preferential loss of solar He by removal of weathered He-rich rim on the grain surface through friction among regolith grains on Itokawa. Residence time of regolith materials on Itokawa is alculated to be shorter than 10 Myr, suggesting that regolith materials of small asteroids would escape easily to space.
Nagane, Satoru; Matsuno, Satoru; Yamamoto, Makoto; Tobinai, Kazuhito; Hori, Hiroshi; Kitahara, Katsumi; Yoshikawa, Seiji
JAEA-Review 2011-001, 49 Pages, 2011/03
Nuclear Facilities Management Section is liquid nuclear waste facility, a small nuclear fuel treatment facility, operation, maintenance and decommissioning of the nuclear ship "MUTSU", which carried out the operation and maintenance services of solid waste facilities. This paper, for the Nuclear Facilities Management Section FY2009 (April 2009 - March 2010) summarized results of operations.
Nagane, Satoru; Matsuno, Satoru; Yamamoto, Makoto; Tobinai, Kazuhito; Ozaki, Shinji; Sato, Yasuo; Kitahara, Katsumi; Yoshikawa, Seiji
JAEA-Review 2009-018, 39 Pages, 2009/08
Nuclear Facilities Management Section is, Liquid nuclear waste facility, a small nuclear fuel treatment facility, operation, maintenance and decommissioning of the nuclear ship "MUTSU", which carried out the operation and maintenance services of solid waste facilities. This paper, the nuclear facilities Management Section, Office of FY2008 year (April 2008-March 2009) summarized results of operations.
Hashimoto, Takashi; Ishiyama, Hironobu*; Watanabe, Yutaka*; Hirayama, Yoshikazu*; Imai, Nobuaki*; Miyatake, Hiroari; Jeong, S.-C.*; Tanaka, Masahiko*; Yoshikawa, Nobuharu*; Nomura, Toru*; et al.
Physics Letters B, 674(4-5), p.276 - 280, 2009/04
Times Cited Count:7 Percentile:47.01(Astronomy & Astrophysics)The excitation function of the Li(d,t)Li reaction was directly measured using Li beams at E = 0.3, 0.4, 0.5, 0.7, 0.8, 1.0, 1.1, and 1.2 MeV with CD targets. The beam energies covered the Gamow peaks for 1310 K. Large cross sections were observed at around E = 0.8 MeV, implying a resonance state located at 22.4 MeV in Be. The present astrophysical reaction rate is higher in one order magnitude than the presently adopted rate at around 110 K.
Yoshikawa, Hiroshi; Sakaki, Hironao; Sako, Hiroyuki; Takahashi, Hiroki; Shen, G.; Kato, Yuko; Ito, Yuichi; Ikeda, Hiroshi*; Ishiyama, Tatsuya*; Tsuchiya, Hitoshi*; et al.
Proceedings of International Conference on Accelerator and Large Experimental Physics Control Systems (ICALEPCS '07) (CD-ROM), p.62 - 64, 2007/10
J-PARC is a large scale facility of the proton accelerators for the multi-purpose of scientific researches in Japan. This facility consists of three accelerators and three experimental stations. Now, J-PARC is under construction, and LINAC is operated for one year, 3GeV synchrotron has just started the commissioning in this October the 1st. The completion of this facility will be next summer. The control system of accelerators established fundamental performance for the initial commissioning. The most important requirement to the control system of this facility is to minimize the activation of accelerator devices. In this paper, we show that the performances of each layer of this control system have been achieved in the initial stage.
Nakahata, Toshihiko*; Yoshikawa, Akira*; Oyaizu, Makoto*; Oya, Yasuhisa*; Ishimoto, Yuki*; Kizu, Kaname; Yagyu, Junichi; Ashikawa, Naoko*; Nishimura, Kiyohiko*; Miya, Naoyuki; et al.
Journal of Nuclear Materials, 367-370(2), p.1170 - 1174, 2007/08
Times Cited Count:3 Percentile:25.42(Materials Science, Multidisciplinary)Retention and desorption behavior of deuterium implanted into pure boron films has been studied by means of the secondary ion mass spectroscopy. It was found that the factor dominating deuterium desorption was the sample temperature. At stage 1, below 573 K, the desorption of deuterium from B-D-B bond dominated and diffusion was the rate-determining process in this stage. Above 573 K, deuterium was mainly desorbed from B-D bonds, and recombination was the rate-determining process in this stage. The effective molecular recombination rate constant of deuterium trapped as B-D bond was determined by an isothermal annealing experiment.
Kojima, Atsushi; Ishii, Kameo*; Miyata, Yoshiaki*; Kakiuchi, Hideto*; Kaido, Norihiro*; Yoshikawa, Masayuki*; Itakura, Akiyoshi*; Ichimura, Makoto*; Chujo, T.*
Fusion Science and Technology, 51(2T), p.274 - 276, 2007/02
Times Cited Count:2 Percentile:18.69(Nuclear Science & Technology)no abstracts in English
Shibahara, Takahiro*; Tanabe, Tetsuo*; Hirohata, Yuko*; Oya, Yasuhisa*; Oyaizu, Makoto*; Yoshikawa, Akira*; Onishi, Yoshihiro*; Arai, Takashi; Masaki, Kei; Okuno, Kenji*; et al.
Journal of Nuclear Materials, 357(1-3), p.115 - 125, 2006/10
Times Cited Count:20 Percentile:78.69(Materials Science, Multidisciplinary)no abstracts in English
Shibahara, Takahiro*; Tanabe, Tetsuo*; Hirohata, Yuko*; Oya, Yasuhisa*; Oyaizu, Makoto*; Yoshikawa, Akira*; Onishi, Yoshihiro*; Arai, Takashi; Masaki, Kei; Okuno, Kenji*; et al.
Nuclear Fusion, 46(10), p.841 - 847, 2006/10
Times Cited Count:18 Percentile:52.24(Physics, Fluids & Plasmas)no abstracts in English
Ishiyama, Hironobu*; Hashimoto, Takashi; Ishikawa, Tomoko*; Watanabe, Yutaka*; Das, S. K.*; Miyatake, Hiroari; Mizoi, Yutaka*; Fukuda, Tomokazu*; Tanaka, Masahiko*; Fuchi, Yoshihide*; et al.
Physics Letters B, 640(3), p.82 - 85, 2006/09
Times Cited Count:33 Percentile:84.87(Astronomy & Astrophysics)The excitation function of the Li(,n)B reaction was measured while identifying the final state event by event in the region of E = 0.7 - 2.6 MeV using a highly efficient detector system and a low-energy Li beam. The results are much improved both in statistics and precisions, and show smaller cross sections than those of previous measurements by a factor of more than 2 in the low-energy region of E 1.5 MeV. A resonance-like structure is found at around E = 0.85 MeV.
Takahashi, Hiroki; Kawase, Masato; Sakaki, Hironao; Yoshikawa, Hiroshi; Ishiyama, Tatsuya*; Ito, Yuichi; Kato, Yuko; Sugimoto, Makoto*; Suzuki, Takahiro*
Proceedings of 3rd Annual Meeting of Particle Accelerator Society of Japan and 31st Linear Accelerator Meeting in Japan (CD-ROM), p.442 - 444, 2006/08
no abstracts in English
Das, S. K.*; Fukuda, Tomokazu*; Mizoi, Yutaka*; Ishiyama, Hironobu*; Miyatake, Hiroari*; Watanabe, Yutaka*; Hirayama, Yoshikazu*; Tanaka, Masahiko*; Yoshikawa, Nobuharu*; Jeong, S.-C.*; et al.
AIP Conference Proceedings 847, p.374 - 376, 2006/07
no abstracts in English
Ishiyama, Hironobu*; Ishikawa, Tomoko*; Hashimoto, Takashi; Watanabe, Yutaka*; Hirayama, Yoshikazu*; Imai, Nobuaki*; Miyatake, Hiroari; Tanaka, Masahiko*; Fuchi, Yoshihide*; Yoshikawa, Nobuharu*; et al.
Nuclear Instruments and Methods in Physics Research A, 560(2), p.366 - 372, 2006/05
Times Cited Count:7 Percentile:47.32(Instruments & Instrumentation)Thanks to the nature of inverse transfer-reactions, low-energy radioactive nuclear beams in light neutron-rich region were produced. The mass-separation and velocity-separation of the JAERI recoil mass-separator help to form high purity beams. The beams of Li, B, and N-RNBs are utilized to the experiments, so far, with those beam intensities and purities of 1.410 pps and 99, 7.810 pps and 98, and 4.710 pps and 98.5, respectively.
Miyahara, Kaname; Yoshikawa, Hideki; Oi, Takao; Shibata, Masahiro; Sawada, Atsushi; Sasamoto, Hiroshi; Iijima, Kazuki; Maekawa, Keisuke; Kawamura, Makoto; Kato, Tomoko; et al.
JAEA-Review 2006-015, 29 Pages, 2006/03
This report is to outline a 5-year plan of research and development (R&D) for performance assessment of geological disposal of high-level radioactive waste in JAEA. This 5-year plan is based on JAEA's mid-term plan which follows the R&D policy specified in "Framework for Nuclear Energy Policy" issued by Japan Atomic Energy Commission. Moreover, research plans for safety regulation issued by Nuclear Safety Commission of Japan should be taken into account. The contents of this 5-year plan follows a framework of R&D issues for performance assessment field established in "the R&D map", i.e. the mid and long term R&D plan for geological disposal of high-level radioactive waste, developed by JNC (predecessor of JAEA) and other relevant R&D organizations. In each research plan, objectives based on the necessity and the significance of the research plan are clarified in the section of "Objectives and the past progresses", with summarizing the progresses of H12: Project to establish the scientific and technical basis for HLW disposal in Japan (Second Progress Report), and H17: Development and management of the technical knowledge base for the geological disposal of HLW (H17 report). In addition, next five year plan is described in the section of "5-year plan (up to Fiscal year Heisei-22)".
Hashimoto, Takashi; Ishiyama, Hironobu*; Ishikawa, Tomoko*; Kawamura, Takashi*; Nakai, Koji*; Watanabe, Yutaka*; Miyatake, Hiroari; Tanaka, Masahiko*; Fuchi, Yoshihide*; Yoshikawa, Nobuharu*; et al.
Nuclear Instruments and Methods in Physics Research A, 556(1), p.339 - 349, 2006/01
Times Cited Count:33 Percentile:88.99(Instruments & Instrumentation)A new type of three dimensional tracking and proportional gas counter has been developed. Adopting a gating-grid system, performance of the detector becomes stable under the injection rate of charged particles less than 410 pps. It is a useful detection system for astrophysical experiments using radioactive nuclear beams, since the efficiency is so high as 100 %.
Ishiyama, Tatsuya*; Yoshikawa, Hiroshi; Sakaki, Hironao; Sako, Hiroyuki; Takahashi, Hiroki; Ito, Yuichi; Kato, Yuko; Kawase, Masato; Ueda, Shinji*; Sugimoto, Makoto*; et al.
Proceedings of 3rd Annual Meeting of Particle Accelerator Society of Japan and 31st Linear Accelerator Meeting in Japan (CD-ROM), p.370 - 372, 2006/00
no abstracts in English