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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：43 Percentile：96.93(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.
Shimizu, Yusei*; Miyake, Atsushi*; Maurya, A.*; Honda, Fuminori*; Nakamura, Ai*; Sato, Yoshiki*; Li, D.*; Homma, Yoshiya*; Yokoyama, Makoto*; Tokunaga, Yo; et al.
Physical Review B, 102(13), p.134411_1 - 134411_11, 2020/10
Times Cited Count：5 Percentile：26.53(Materials Science, Multidisciplinary)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：259 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.
Sakai, Akihiro; Kurosawa, Ryohei*; Nakata, Hisakazu; Okada, Shota; Izumo, Sari; Sato, Makoto*; Kitamura, Yoichi*; Honda, Yasutake*; Takaoka, Katsuki*; Amazawa, Hiroya
JAEA-Technology 2016-019, 134 Pages, 2016/10
JAEA-Technology-2016-019.pdf:8.25MB
Japan Atomic Energy Agency has been developing to design trench disposal facility with impermeable layers in order to dispose of miscellaneous waste. Geomembrane liners have a function that prevent seepage of leachant and collect the leachant. However, the geomembrane liners do not necessarily provide the expected performance due to damage generated when heavy equipment contacts with the liner. Therefore, we studied the impermeable layers having high performance of preventing seepage of leachant including radioactivity taking into account characteristics of low permeable materials and effect of multiple layer structure. As results, we have evaluated that the composite layers composed by a drainage layer, geomembrane liners and a low permeable layer are most effective structure to prevent seepage of leachant. Taking into account disposal of waste including cesium, we also considered zeolite containing sheets for adsorption of cesium were installed in the impermeable layers.
Kohashi, Akio; Onoe, Hironori; Yamamoto, Shinya*; Honda, Makoto*; Sakurai, Hideyuki*; Masumoto, Kiyoshi*
JAEA-Research 2015-022, 89 Pages, 2016/03
JAEA-Research-2015-022.pdf:27.85MB
In Japan, high-level radioactive waste (HLW) will be emplaced in a stable host rock formation deeper than 300 meters underground for geological disposal. It is important to understand heterogeneous distribution of hydraulic conductivity from the viewpoints of the safety assessment of geological disposal of HLW and construction of underground facilities. Inverse analysis based on the transient data is an efficient technique for estimating the heterogeneous distribution. In this study, numerical experiments with the adjoint state method and the ensemble Kalman filter were carried out in order to understand effective method for application of these inverse analysis. As a result of this study, the capability of each analysis techniques was shown.
Nishimori, Nobuyuki; Nagai, Ryoji; Matsuba, Shunya; Hajima, Ryoichi; Yamamoto, Masahiro*; Miyajima, Tsukasa*; Honda, Yosuke*; Uchiyama, Takashi*; Iijima, Hokuto*; Kuriki, Masao*; et al.
Proceedings of 10th Annual Meeting of Particle Accelerator Society of Japan (Internet), p.174 - 178, 2014/06
no abstracts in English
500 kVNishimori, Nobuyuki; Nagai, Ryoji; Matsuba, Shunya; Hajima, Ryoichi; Yamamoto, Masahiro*; Honda, Yosuke*; Miyajima, Tsukasa*; Iijima, Hokuto*; Kuriki, Masao*; Kuwahara, Makoto*
Physical Review Special Topics; Accelerators and Beams, 17(5), p.053401_1 - 053401_17, 2014/05
Times Cited Count：23 Percentile：80.23(Physics, Nuclear)Nishimori, Nobuyuki; Nagai, Ryoji; Matsuba, Shunya; Hajima, Ryoichi; Yamamoto, Masahiro*; Honda, Yosuke*; Miyajima, Tsukasa*; Iijima, Hokuto*; Kuriki, Masao*; Kuwahara, Makoto*
Proceedings of 35th International Free-Electron Laser Conference (FEL 2013) (Internet), p.184 - 188, 2013/08
Nishimori, Nobuyuki; Nagai, Ryoji; Matsuba, Shunya; Hajima, Ryoichi; Yamamoto, Masahiro*; Miyajima, Tsukasa*; Honda, Yosuke*; Iijima, Hokuto*; Kuriki, Masao*; Kuwahara, Makoto*; et al.
Proceedings of 9th Annual Meeting of Particle Accelerator Society of Japan (Internet), p.255 - 259, 2013/08
no abstracts in English
Nishimori, Nobuyuki; Nagai, Ryoji; Matsuba, Shunya; Hajima, Ryoichi; Yamamoto, Masahiro*; Miyajima, Tsukasa*; Honda, Yosuke*; Iijima, Hokuto*; Kuriki, Masao*; Kuwahara, Makoto*
Applied Physics Letters, 102(23), p.234103_1 - 234103_4, 2013/06
Times Cited Count：20 Percentile：63.34(Physics, Applied)Nishimori, Nobuyuki; Nagai, Ryoji; Matsuba, Shunya; Hajima, Ryoichi; Yamamoto, Masahiro*; Honda, Yosuke*; Miyajima, Tsukasa*; Iijima, Hokuto*; Kuriki, Masao*; Kuwahara, Makoto*
Proceedings of 4th International Particle Accelerator Conference (IPAC '13) (Internet), p.321 - 323, 2013/05
Nishimori, Nobuyuki; Nagai, Ryoji; Matsuba, Shunya; Hajima, Ryoichi; Yamamoto, Masahiro*; Honda, Yosuke*; Miyajima, Tsukasa*; Iijima, Hokuto*; Kuriki, Masao*; Kuwahara, Makoto*; et al.
Proceedings of 34th International Free Electron Laser Conference (FEL 2012) (Internet), p.161 - 164, 2012/08
Nishimori, Nobuyuki; Nagai, Ryoji; Hajima, Ryoichi; Yamamoto, Masahiro*; Miyajima, Tsukasa*; Honda, Yosuke*; Iijima, Hokuto*; Kuriki, Masao*; Kuwahara, Makoto*; Okumi, Shoji*; et al.
Proceedings of 8th Annual Meeting of Particle Accelerator Society of Japan (Internet), p.20 - 23, 2011/08
no abstracts in English
Nishimori, Nobuyuki; Nagai, Ryoji; Yamamoto, Masahiro*; Honda, Yosuke*; Miyajima, Tsukasa*; Iijima, Hokuto*; Kuriki, Masao*; Kuwahara, Makoto*; Okumi, Shoji*; Nakanishi, Tsutomu*; et al.
Journal of Physics; Conference Series, 298, p.012005_1 - 012005_6, 2011/06
Yamamoto, Shinya*; Honda, Makoto*; Sakurai, Hideyuki*; Suzuki, Makoto*; Sanada, Hiroyuki; Sugita, Yutaka; Matsui, Hiroya
Proceedings of 14th Annual Conference of the International Association for Mathematical Geosciences (IAMG 2010) (CD-ROM), 12 Pages, 2010/09
The distribution of groundwater properties is important for understanding of the deep underground hydrogeological environments in the design of the HLW disposal facilities. This study proposes a geostatistical system for modeling the chemical properties of groundwater which have a correlation with the resistivity data obtained from widespread and exhaustive survey. The proposed system is consists of two methodologies (resistivity data integration using Simple Kriging with varying local mean (SKlm) and 3D distribution modeling of hydro-chemical properties of groundwater estimated by SKlm algorithm). 2 types of uncertainty are considered: (1) Aleatory uncertainty; (2) Epistemic uncertainty. As a result, the uncertainties of the proposal model have been estimated lower than other traditional model's.
Nishimori, Nobuyuki; Nagai, Ryoji; Hajima, Ryoichi; Yamamoto, Masahiro*; Honda, Yosuke*; Miyajima, Tsukasa*; Muto, Toshiya*; Iijima, Hokuto*; Kuriki, Masao*; Kuwahara, Makoto*; et al.
Proceedings of 25th International Linear Accelerator Conference (LINAC 2010) (CD-ROM), p.995 - 997, 2010/09
Honda, Makoto*; Yamamoto, Shinya*; Sakurai, Hideyuki*; Suzuki, Makoto*; Sanada, Hiroyuki; Sugita, Yutaka; Matsui, Hiroya
Doboku Gakkai Rombunshu, C, 66(3), p.609 - 624, 2010/08
This paper proposes a geostatistical system for modeling the groundwater properties which have a correlation with the ground resistivity data obtained from widespread and exhaustive electromagnetic survey. That is, the methodology for the integration of resistivity data measured by various methods and the methodology for modeling the groundwater properties using the integrated resistivity data has been developed. The proposed system has also been validated using the data obtained in the surface-based investigations of the Horonobe URL project. Additionally, the quantification of uncertainties in the estimated model has been tried by numerical simulations based on the data. As a result, the uncertainties of the proposal model have been estimated lower than other traditional model's.
Nagai, Ryoji; Nishimori, Nobuyuki; Hajima, Ryoichi; Muto, Toshiya*; Yamamoto, Masahiro*; Miyajima, Tsukasa*; Honda, Yosuke*; Iijima, Hokuto*; Kuriki, Masao*; Kuwahara, Makoto*; et al.
Proceedings of 7th Annual Meeting of Particle Accelerator Society of Japan (DVD-ROM), p.806 - 808, 2010/08
A 500-kV, 10-mA photocathode DC gun which is designed for next-generation light- sources based on energy-recovery linac has been developed in a collaboration effort of JAEA, KEK, Hiroshima University and Nagoya University. We have utilized a segmented cylindrical ceramic insulator and guard-ring electrodes to prevent any damage to the insulator from electrons emitted by the support-rod electrode. The 500-kV gun was successfully conditioned up to a voltage of 550 kV and a long-time holding test for 8 h was demonstrated at an acceleration voltage of 500 kV. The cathode electrode, anode electrode, and beam line apparatuses are now under fabrication and beam tests of the gun will be started soon.
Nishimori, Nobuyuki; Nagai, Ryoji; Hajima, Ryoichi; Yamamoto, Masahiro*; Miyajima, Tsukasa*; Honda, Yosuke*; Muto, Toshiya*; Iijima, Hokuto*; Kuriki, Masao*; Kuwahara, Makoto*; et al.
Proceedings of 7th Annual Meeting of Particle Accelerator Society of Japan (DVD-ROM), p.802 - 805, 2010/08
no abstracts in English
Yamamoto, Masahiro*; Uchiyama, Takashi*; Miyajima, Tsukasa*; Honda, Yosuke*; Sato, Kotaro*; Matsuba, Shunya*; Saito, Yoshio*; Kobayashi, Masanori*; Kurisu, Hiriki*; Hajima, Ryoichi; et al.
Proceedings of 7th Annual Meeting of Particle Accelerator Society of Japan (DVD-ROM), p.717 - 720, 2010/08
A 500-kV photocathode DC electron gun which can supply the beam of a low emittance and a high average current has been developed in collaboration with KEK, JAEA, Hiroshima Univ., Nagoya Univ. and Yamaguchi Univ. The vacuum of the gun chamber has to be lower Extreme High Vacuum for maintain cathode-life time. A titanium chamber and new material of ceramic were employed to reduce outgassing rate. The result of outgassing rate of the gun chamber is described in this report.
