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Okudaira, Takuya*; Tani, Yuika*; Endo, Shunsuke; Doskow, J.*; Fujioka, Hiroyuki*; Hirota, Katsuya*; Kameda, Kento*; Kimura, Atsushi; Kitaguchi, Masaaki*; Luxnat, M.*; et al.
Physical Review C, 107(5), p.054602_1 - 054602_7, 2023/05
Times Cited Count:1 Percentile:68.16(Physics, Nuclear)no abstracts in English
Chen, J.*; Yamamoto, Kei; Zhang, J.*; Ma, J.*; Wang, H.*; Sun, Y.*; Chen, M.*; Ma, J.*; Liu, S.*; Gao, P.*; et al.
Physical Review Applied (Internet), 19(2), p.024046_1 - 024046_9, 2023/02
Times Cited Count:4 Percentile:90.23(Physics, Applied)Okita, Hidefumi; Tamura, Fumihiko; Yamamoto, Masanobu; Nomura, Masahiro; Shimada, Taihei; Yoshii, Masahito*; Omori, Chihiro*; Sugiyama, Yasuyuki*; Hasegawa, Katsushi*; Hara, Keigo*; et al.
Journal of Physics; Conference Series, 2420, p.012092_1 - 012092_6, 2023/01
A power upgrade of existing 8 kW solid-state driver amplifier is required for the acceleration of high intensity proton beams on the J-PARC 3 GeV rapid cycling synchrotron. The development of a 25 kW amplifier with gallium nitride (GaN) HEMTs, based on 6.4 kW modules is on going. The combiner is a key component to achieve such a high output power over the wide bandwidth required for multi-harmonic rf operation. This paper presents preliminary design of the combiner. The circuit simulation setup and results, including the realistic magnetic core characteristics and frequency response of the cable are reported.
Lee, O.*; Yamamoto, Kei; Umeda, Maki; Zollitsch, C. W.*; Elyasi, M.*; Kikkawa, Takashi*; Saito, Eiji; Bauer, G. E. W.*; Kurebayashi, Hidekazu*
Physical Review Letters, 130(4), p.046703_1 - 046703_6, 2023/01
Times Cited Count:5 Percentile:80.44(Physics, Multidisciplinary)Yamamoto, Shingo*; Fujii, Takuto*; Luther, S.*; Yasuoka, Hiroshi*; Sakai, Hironori; Brtl, F.*; Ranjith, K. M.*; Rosner, H.*; Wosnitza, J.*; Strydom, A. M.*; et al.
Physical Review B, 106(11), p.115125_1 - 115125_5, 2022/09
Times Cited Count:0 Percentile:0(Materials Science, Multidisciplinary)We have studied the microscopic magnetic properties, the nature of the 130 K phase transition, and the ground state in the recently synthesized compound CeRhGa by use of Ga nuclear quadrupole resonance (NQR). The NQR spectra clearly show an unusual phase transition at K, yielding a splitting of the high-temperature single NQR line into two well-resolved NQR lines, providing evidence for two crystallographically inequivalent Ga sites. The NQR frequencies are in good agreement with fully relativistic calculations of the band structure. Our NQR results indicate the absence of magnetic or charge order down to 0.3 K. The temperature dependence of the spin-lattice relaxation rate shows three distinct regimes, with onset temperatures at and 2 K. The temperature-independent , observed between and 2 K, crosses over to a Korringa process, , below 2 K, which evidences a rare two-ion Kondo scenario: The system evolves into a dense Kondo coherent state below 2.0 and 0.8 K probed by the two different Ga sites.
Kato, Atsushi; Yamamoto, Tomohiko; Ando, Masato; Chikazawa, Yoshitaka; Murakami, Hisatomo*; Oyama, Kazuhiro*; Kaneko, Fumiaki*; Higurashi, Koichi*; Chanteclair, F.*; Chenaud, M.-S.*; et al.
EPJ Nuclear Sciences & Technologies (Internet), 8, p.11_1 - 11_10, 2022/06
This paper provides an overview of plant system studies to establish a common technical view for Sodium-cooled Fast Reactor concept between France and Japan based on ASTRID600 and the new concept with downsized output called ASTRID150. One of important issues on a reactor structure design is to enhance seismic resistance to be tolerable against strong earthquake such that postulated in Japan. A concept of High Frequency Design is shared, and the design options related to HFD have been examined and design recommendations are established. In addition, this paper include results of studies for a steam generator, a decay heat removal system, a fuel handling system and a containment vessel.
Hayashi, Koichi*; Lederer, M.*; Fukumoto, Yohei*; Goto, Masashi*; Yamamoto, Yuta*; Happo, Naohisa*; Harada, Masahide; Inamura, Yasuhiro; Oikawa, Kenichi; Oyama, Kenji*; et al.
Applied Physics Letters, 120(13), p.132101_1 - 132101_6, 2022/03
Times Cited Count:0 Percentile:0(Physics, Applied)Yamamoto, Kei; Xu, M.*; Puebla, J.*; Otani, Yoshichika*; Maekawa, Sadamichi*
Journal of Magnetism and Magnetic Materials, 545, p.168672_1 - 168672_10, 2022/03
Times Cited Count:10 Percentile:52.49(Materials Science, Multidisciplinary)Zhang, J.*; Chen, M.*; Chen, J.*; Yamamoto, Kei; Wang, H.*; Hamdi, M.*; Sun, Y.*; Wagner, K.*; He, W.*; Zhang, Y.*; et al.
Nature Communications (Internet), 12, p.7258_1 - 7258_8, 2021/12
Times Cited Count:14 Percentile:77.64(Multidisciplinary Sciences)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.
Amekura, Hiroshi*; Toulemonde, M.*; Narumi, Kazumasa*; Li, R.*; Chiba, Atsuya*; Hirano, Yoshimi*; Yamada, Keisuke*; Yamamoto, Shunya*; Ishikawa, Norito; Okubo, Nariaki; et al.
Scientific Reports (Internet), 11(1), p.185_1 - 185_11, 2021/01
Times Cited Count:12 Percentile:75.03(Multidisciplinary Sciences)We report the track formation of 10 nm in diameter in silicon irradiated with 6 MeV C, i.e., much lower energy than the previously reported energy threshold.
Yamamoto, Kei; Yu, W.*; Yu, T.*; Puebla, J.*; Xu, M.*; Maekawa, Sadamichi*; Bauer, G.*
Journal of the Physical Society of Japan, 89(11), p.113702_1 - 113702_5, 2020/11
Times Cited Count:10 Percentile:62.22(Physics, Multidisciplinary)Xu, M.*; Yamamoto, Kei; Puebla, J.*; Baumgaertl, K.*; Rana, B.*; Miura, Katsuya*; Takahashi, Hiromasa*; Grundler, D.*; Maekawa, Sadamichi*; Otani, Yoshichika*
Science Advances (Internet), 6(32), p.eabb1724_1 - eabb1724_4, 2020/08
Times Cited Count:81 Percentile:97.1(Multidisciplinary Sciences)Puebla, J.*; Xu, M.*; Rana, B.*; Yamamoto, Kei; Maekawa, Sadamichi*; Otani, Yoshichika*
Journal of Physics D; Applied Physics, 53(26), p.264002_1 - 264002_7, 2020/06
Times Cited Count:31 Percentile:87.05(Physics, Applied)Heussner, F.*; Talmelli, G.*; Geilen, M.*; Heinz, B.*; Brcher, T.*; Meyer, T.*; Ciubotaru, F.*; Adelmann, C.*; Yamamoto, Kei; Serga, A. A.*; et al.
Physica Status Solidi; Rapid Research Letters, 14(4), p.1900695_1 - 1900695_6, 2020/04
Times Cited Count:31 Percentile:87.61(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.
Pospil, J.*; Haga, Yoshinori; Kohama, Yoshimitsu*; Miyake, Atsushi*; Kambe, Shinsaku; Tateiwa, Naoyuki; Valika, M.*; Proschek, P.*; Prokleka, J.*; Sechovsk, V.*; et al.
Physical Review B, 98(1), p.014430_1 - 014430_7, 2018/07
Times Cited Count:16 Percentile:61.77(Materials Science, Multidisciplinary)Tanaka, Taiki*; Narikiyo, Yoshihiro*; Morita, Kosuke*; Fujita, Kunihiro*; Kaji, Daiya*; Morimoto, Koji*; Yamaki, Sayaka*; Wakabayashi, Yasuo*; Tanaka, Kengo*; Takeyama, Mirei*; et al.
Journal of the Physical Society of Japan, 87(1), p.014201_1 - 014201_9, 2018/01
Times Cited Count:18 Percentile:74.47(Physics, Multidisciplinary)Excitation functions of quasielastic scattering cross sections for the Ca + Pb, Ti + Pb, and Ca + Cm reactions were successfully measured by using the gas-filled recoil-ion separator GARIS. Fusion barrier distributions were extracted from these data, and compared with the coupled-channels calculations. It was found that the peak energies of the barrier distributions for the Ca + Pb and Ti + Pb systems coincide with those of the 2n evaporation channel cross sections for the systems, while that of the Ca + Cm is located slightly below the 4n evaporation ones. This results provide us helpful information to predict the optimum beam energy to synthesize superheavy nuclei.
Michel-Sendis, F.*; Gauld, I.*; Martinez, J. S.*; Alejano, C.*; Bossant, M.*; Boulanger, D.*; Cabellos, O.*; Chrapciak, V.*; Conde, J.*; Fast, I.*; et al.
Annals of Nuclear Energy, 110, p.779 - 788, 2017/12
Times Cited Count:65 Percentile:99.16(Nuclear Science & Technology)Yamamoto, Masahiko; Holland, M. K.*; Cordaro, J. V.*; Kuno, Takehiko; Surugaya, Naoki
JAEA-Technology 2017-014, 63 Pages, 2017/06
In this study, the controlled-potential coulometry has been applied as a primary method for characterizing the Pu master solutions being used as alternative source material for IDMS spikes. The coulometry system compliance with ISO12183 has been used for measurement. It has been calibrated using equipment traceable to the SI units. Plutonium standard samples have been measured to confirm the accuracy. The relative standard deviation is below 0.05%. The results agree with the reference value within 0.05%. It is found that the Pu can be precisely analyzed by the coulometry system. Then, the Pu nitrate solution, which has been purified from mixed oxide powder containing relatively high Pu, has been measured. The relative standard deviation is below 0.05%. The relative expanded uncertainty is less than 0.074% at the 95% confidence interval (k=2). It is indicated that coulometric assay of Pu is fit for the purpose of characterizing reference materials.