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Onoue, Tetsuji*; Sato, Honami*; Nakamura, Tomoki*; Noguchi, Takaaki*; Hidaka, Yoshihiro*; Shirai, Naoki*; Ebihara, Mitsuru*; Osawa, Takahito; Hatsukawa, Yuichi; Toh, Yosuke; et al.
Proceedings of the National Academy of Sciences of the United States of America, 109(47), p.19134 - 19139, 2012/11
Times Cited Count：40 Percentile：72.81(Multidisciplinary Sciences)The 34 million year (My) interval of the Late Triassic is marked by the formation of several large impact structures on Earth. As with the Chicxulub impact event at the Cretaceous/Paleogene boudary, the Late Triassic impact events have been considered a factor in biotic extinction events in the Late Triassic (e.g., the Triassic/Jurassic boundary). However, the causal link between these impact events and a mass extinction event in the Late Triassic remains controversial because of a lack of stratigraphic records of their ejecta deposits. Here we report evidence for an impact event (platinum group elements anomaly, nickel-rich magnetite and microspherules) deposited within a Paleo-Pacific basin in the middle Norian (Upper Triassic) deep-sea sediment in Japan. This includes anomalously high abundances of iridium, up to 41.5 parts per billion (ppb), in the ejecta deposit, which suggests that the iridium anomaly may be found on a global scale. The middle Norian age of the ejecta deposit suggests that the impact event that produced the 100-km-wide Manicouagan crater in Canada8 is most likely related to its deposition. Our analysis of siliceous microfossils shows no evidence of a mass extinction event across the impact event horizon, and no contemporaneous faunal turnover is seen in other marine fossils. However, such an event has been reported among terrestrial tetrapods and floras in North America. We therefore hypothesize that the Manicouagan impact caused the catastrophic collapse of terrestrial ecosystems near the impact site, but not within the marine realm.
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：130 Percentile：95.22(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.
Umemori, Kensei*; Furuya, Takaaki*; Kako, Eiji*; Noguchi, Shuichi*; Sakai, Hiroshi*; Sato, Masato*; Shishido, Toshio*; Watanabe, Ken*; Yamamoto, Yasuchika*; Shinoe, Kenji*; et al.
Proceedings of 15th International Conference on RF Superconductivity (SRF 2011) (Internet), p.956 - 961, 2011/07
The Compact ERL (cERL) project is advanced in Japan. Its aim is to demonstrate the circulation of 100 mA electron beams with energy of 35-200 MeV. Superconducting cavities are key components for realizing ERL and used for injector part and main linac part. Critical issue for the injector part is the development of input power coupler. Prototype input couplers were fabricated and high power test was performed. Cooling ability of HOM coupler is also important for CW operation of cavity. At main linac part, HOM damped 9-cell cavities are applied to avoid BBU instabilities. Prototypes were fabricated for the cavity, the input coupler and the HOM absorber. Their performance was investigated. For both parts, cryomodules are under construction and will be completed in 2012.
Osawa, Takahito; Yamamoto, Yukio*; Noguchi, Takaaki*; Iose, Akari*; Nagao, Keisuke*
Meteoritics & Planetary Science, 45(8), p.1320 - 1339, 2010/08
Times Cited Count：12 Percentile：35.51(Geochemistry & Geophysics)The interior texture and chemical and noble gas composition of 99 cosmic spherules collected from the meteorite ice field around the Yamato Mountains in Antarctica were investigated. Their textures were used to classify the spherules into six different types reflecting the degree of heating. An enigmatic spherule, labeled M240410, had an extremely high concentration of cosmogenic nuclides. Assuming 4
exposure to galactic and solar cosmic rays as a micrometeoroid and no exposure on the parent body, the cosmic-ray exposure (CRE) age of 393 Myr could be computed using cosmogenic 
Ne. Under these model assumptions, the inferred age suggests that the particle might have been an Edgeworth-Kuiper Belt object. Alternatively, if exposure near the surface of its parent body was dominant, the CRE age of 382 Myr can be estimated from the cosmogenic 
Ar using the production rate of the 2 exposure geometry, and implies that the particle may have originated in the mature regolith of an asteroid.
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.
Sakai, Hiroshi*; Furuya, Takaaki*; Kako, Eiji*; Noguchi, Shuichi*; Sato, Masato*; Sakanaka, Shogo*; Shishido, Toshio*; Takahashi, Takeshi*; Umemori, Kensei*; Watanabe, Ken*; et al.
Proceedings of 45th Advanced ICFA Beam Dynamics Workshop on Energy Recovery Linacs (ERL '09) (Internet), p.57 - 62, 2010/05
Development of a SC Cavity Injector Cryomodule and Main linac Cryomodule for the compact ERL is being continued at KEK since 2006. Design of an injector cryomodule containing three 2-cell 1.3-GHz cavities for Injector Cryomodule and two 9-cell 1.3-GHz cavities for Main linac Cryomodule are almost completed. Status of R&D and design details are reported.
Umemori, Kensei*; Furuya, Takaaki*; Kako, Eiji*; Noguchi, Shuichi*; Sakai, Hiroshi*; Sato, Masato*; Shishido, Toshio*; Takahashi, Takeshi*; Watanabe, Ken*; Yamamoto, Yasuchika*; et al.
Proceedings of 14th International Conference on RF Superconductivity (SRF 2009) (Internet), p.896 - 901, 2009/09
Construction of the Compact ERL is planned in Japan, in order to test the key technology to realize a future ERL based X-ray light source. The operation of 60-200 MeV beam energy and 100 mA beam current are proposed. The superconducting cavity is one of the key components and applied for the injector part and the main linac part. At the injector part, most challenging issue is an input coupler, which has to handle more than 300 kW input power per cavity. On the other hand, strong HOM damping is required for the main linac, in order to avoid beam instabilities and large heat load at cryomodules. Status of cavity developments, together with cryomodule developments, including input couplers and HOM couplers/absorbers, are described in this paper.
Sakanaka, Shogo*; Ago, Tomonori*; Enomoto, Atsushi*; Fukuda, Shigeki*; Furukawa, Kazuro*; Furuya, Takaaki*; Haga, Kaiichi*; Harada, Kentaro*; Hiramatsu, Shigenori*; Honda, Toru*; et al.
Proceedings of 11th European Particle Accelerator Conference (EPAC '08) (CD-ROM), p.205 - 207, 2008/06
Future synchrotron light sources based on the energy-recovery linacs (ERLs) are expected to be capable of producing super-brilliant and/or ultra-short pulses of synchrotron radiation. Our Japanese collaboration team is making efforts for realizing an ERL-based hard X-ray source. We report recent progress in our R&D efforts.
Sawamura, Masaru; Umemori, Kensei*; Sakanaka, Shogo*; Suwada, Tsuyoshi*; Takahashi, Takeshi*; Furuya, Takaaki*; Noguchi, Shuichi*; Kako, Eiji*; Shishido, Toshio*; Watanabe, Ken*; et al.
no journal, ,
Superconducting accelerator cavities are essential for the energy-recovery linac. The superconducting cavities are used in an injector and a main linac. A new model has been designed for the ERL. A center-single-cell cavity, an end-single-cell cavity and 9-cell cavity have been constructed. Vertical tests were performed for the center-single-cell cavity and the end-single cell cavity. A 2-cell cavity for the injector is under construction.
Sato, Honami*; Onoue, Tetsuji*; Nakamura, Tomoki*; Noguchi, Takaaki*; Hatsukawa, Yuichi; Osawa, Takahito; Toh, Yosuke; Koizumi, Mitsuo
no journal, ,
Microspherules were discovered from a claystone layer (5 cm thick) in an Upper Triassic bedded chert succession of the Sakahogi section, Mino Terrane, Japan. An analysis of radiolarian fossils reveals that the claystone layer is correlated with the early to middle Norian stage of the Upper Triassic. The base of the layer contains 10-15% (by rock volume) green microspherules. Microspherules range in size from 200 to 300 microns. Synchrotron X-ray diffraction analysis indicates that the microspherules are composed mainly of clinoclore. Some microspherules contain a high proportion of small, euhedral to subhedral crystals of oxidized Ni-rich spinels. They are distinguished from typical igneous spinels by high contents of NiO and Fe
. The geochemical signals of extraterrestrial impact are recorded in the claystone layer. Examination of the clay layer using a multiple 
-ray analysis system after neutron activation reveals that microspherules and Ni-rich spinels occur associated with an iridium anomaly, which levels comparable with those at the Cretaceous-Paleogene boudary. A scanning X-ray analytical microscope analysis shows high concentrations of siderophile elements such as nickel and cobalt, which would be expected from an extraterrestrial source.
Yamagishi, Akihiko*; Yokobori, Shinichi*; Hashimoto, Hirofumi*; Yano, Hajime*; Imai, Eiichi*; Okudaira, Kyoko*; Kawai, Hideyuki*; Kobayashi, Kensei*; Tabata, Makoto*; Nakagawa, Kazumichi*; et al.
no journal, ,
no abstracts in English
Osawa, Takahito; Ninomiya, Kazuhiko*; Nakamura, Tomoki*; Takahashi, Tadayuki*; Terada, Kentaro*; Yurimoto, Hisayoshi*; Noguchi, Takaaki*; Okazaki, Ryuji*; Yabuta, Hikaru*; Naraoka, Hiroshi*; et al.
no journal, ,
I report on the muonic X-ray analysis experiment conducted at J-PARC from 2020 to 2021, in which the analytical method was significantly developed through four preliminary experiments and successfully analyzed samples from the asteroid Ryugyu in July 2021. The experimental process is described from a radiochemical point of view.
