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rays from the 
-wave resonance of 
SnKoga, Jun*; Takada, Shusuke*; Endo, Shunsuke; Fujioka, Hiroyuki*; Hirota, Katsuya*; Ishizaki, Kohei*; Kimura, Atsushi; Kitaguchi, Masaaki*; Niinomi, Yudai*; Okudaira, Takuya*; et al.
Physical Review C, 105(5), p.054615_1 - 054615_5, 2022/05
Times Cited Count：3 Percentile：66.85(Physics, Nuclear)no abstracts in English
Tanaka, Hirohisa*; Masaki, Sayaka*; Aotani, Takuro*; Inagawa, Kohei*; Iwata, Sogo*; Aida, Tatsuya*; Yamamoto, Tadasuke*; Kita, Tomoaki*; Ono, Hitomi*; Takenaka, Keisuke*; et al.
SAE Technical Paper 2022-01-0534 (Internet), 10 Pages, 2022/03
Noma, Yuichiro*; Kotegawa, Hisashi*; Kubo, Tetsuro*; To, Hideki*; Harima, Hisatomo*; Haga, Yoshinori; Yamamoto, Etsuji; Onuki, Yoshichika*; Ito, Kohei*; Nakamura, Ai*; et al.
Journal of the Physical Society of Japan, 90(7), p.073707_1 - 073707_5, 2021/07
Times Cited Count：0 Percentile：0(Physics, Multidisciplinary) rays in the 
La(
)
La
reactionOkudaira, Takuya*; Endo, Shunsuke; Fujioka, Hiroyuki*; Hirota, Katsuya*; Ishizaki, Kohei*; Kimura, Atsushi; Kitaguchi, Masaaki*; Koga, Jun*; Niinomi, Yudai*; Sakai, Kenji; et al.
Physical Review C, 104(1), p.014601_1 - 014601_6, 2021/07
Times Cited Count：4 Percentile：57.13(Physics, Nuclear)Kawasaki, Kohei; Shinada, Kenta; Okamoto, Naritoshi; Kageyama, Tomio; Eda, Takashi; Okazaki, Hiro; Suzuki, Hiromichi; Yamamoto, Kazuya; Otabe, Jun
JAEA-Technology 2020-025, 80 Pages, 2021/03
JAEA-Technology-2020-025.pdf:3.72MB
Plutonium Fuel Production Facility was built in 1988 for the purpose of mainly producing MOX fuel of the prototype fast breeder reactor MONJU, and large glove boxes were installed for handling unsealed nuclear fuel material remotely. The panels of these glove boxes are made of acrylic, except for those installed after December 2013. For fires inside the glove box, automatic fire extinguishing systems using halides have been introduced since the beginning of construction, but for fires outside the glove box, there have been issues with direct measures for acrylic. Therefore, we have developed a fireproof sheet that mitigates the effect of fire outside the glove box on the panels as much as possible. As a result, fire-retardant sheets have been selected and attached to the glove box panels. We conducted a flammability test of the acrylic plate attached with these fireproof sheets and a usage environment influence test of fireproof sheets, and obtained good results. In addition, we set up a working group in the Plutonium Fuel Development Center in view of reducing external exposure during the work of attaching fireproof sheets, in which we discussed and examined the work procedure, and summarized it in the basic procedure manual.
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.
rays from neutron-induced compound states of LaYamamoto, Tomoki*; Okudaira, Takuya; Endo, Shunsuke; Fujioka, Hiroyuki*; Hirota, Katsuya*; Ino, Takashi*; Ishizaki, Kohei*; Kimura, Atsushi; Kitaguchi, Masaaki*; Koga, Jun*; et al.
Physical Review C, 101(6), p.064624_1 - 064624_8, 2020/06
Times Cited Count：9 Percentile：73.66(Physics, Nuclear)
production from methane decomposition by fullerene at low temperatureTokunaga, Tomoharu*; Kuno, Kohei*; Kawakami, Takumi*; Yamamoto, Takahisa*; Yoshigoe, Akitaka
International Journal of Hydrogen Energy, 45(28), p.14347 - 14353, 2020/05
Times Cited Count：2 Percentile：6.8(Chemistry, Physical)To understand the catalytic behavior of graphite and carbon black with mainly 6-membered rings with sp
bonds for H production by CH
decomposition, fullerenes with 6-membered rings and also those comprising 5- and 7-membered rings with sp bonds was investigated using gas chromatography, XPS and TEM analysis. From these analysis, it is anticipated that the ring structures without 6-membered rings in carbon materials with sp bonding contribute to the catalytic behavior for CH decomposition at a low temperature of 400C.
-rays after neutron capture by La for a T-violation searchOkudaira, Takuya; Shimizu, Hirohiko*; Kitaguchi, Masaaki*; Hirota, Katsuya*; Haddock, C. C.*; Ito, Ikuya*; Yamamoto, Tomoki*; Endo, Shunsuke*; Ishizaki, Kohei*; Sato, Takumi*; et al.
EPJ Web of Conferences, 219, p.09001_1 - 09001_6, 2019/12
Parity violating effects enhanced by up to 10
times have been observed in several neutron induced compound nuclei. There is a theoretical prediction that time reversal (T) violating effects can also be enhanced in these nuclei implying that T-violation can be searched for by making very sensitive measurements. However, the enhancement factor has not yet been measured in all nuclei. The angular distribution of the (n,) reaction was measured with La by using a germanium detector assembly at J-PARC, and the enhancement factor was obtained. From the result, the measurement time to achieve the most sensitive T-violation search was estimated as 1.4 days, and a 40% polarized La target and a 70% polarized 
He spin filter whose thickness is 70 atm
cm are needed. Therefore high quality He spin filter is developed in JAEA. The measurement result of the (n,) reaction at J-PARC and the development status of the He spin filter will be presented.
CrMnO
thin filmsYoshimatsu, Kohei*; Ishimaru, Junya*; Watarai, Keisuke*; Yamamoto, Kohei*; Hirata, Yasuyuki*; Wadachi, Hiroki*; Takeda, Yukiharu; Horiba, Koji*; Kumigashira, Hiroshi*; Sakata, Osami*; et al.
Physical Review B, 99(23), p.235129_1 - 235129_8, 2019/06
Times Cited Count：10 Percentile：49.82(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.
Sasaki, Hirokazu*; Nishikubo, Hideo*; Nishida, Shinsuke*; Yamazaki, Satoshi*; Nakasaki, Ryusuke*; Isomatsu, Takemi*; Minato, Ryuichiro*; Kinugawa, Kohei*; Imamura, Akihiro*; Otomo, Shinya*; et al.
Furukawa Denko Jiho, (138), p.2 - 10, 2019/02
no abstracts in English
; 
Ge-NQR study at ambient pressureNoma, Yuichiro*; Kotegawa, Hisashi*; Kubo, Tetsuro*; To, Hideki*; Harima, Hisatomo*; Haga, Yoshinori; Yamamoto, Etsuji; Onuki, Yoshichika*; Ito, Kohei*; Haller, E. E.*; et al.
Journal of the Physical Society of Japan, 87(3), p.033704_1 - 033704_5, 2018/03
Times Cited Count：4 Percentile：35.9(Physics, Multidisciplinary)Ino, Kohei*; Konno, Yuta*; Kozuka, Mariko*; Hirota, Akinari*; Togo, Yoko*; Fukuda, Akari*; Komatsu, Daisuke*; Tsunogai, Urumu*; Tanabe, Akifumi*; Yamamoto, Satoshi*; et al.
Environmental Microbiology Reports (Internet), 8(2), p.285 - 294, 2016/04
Times Cited Count：26 Percentile：68.59(Environmental Sciences)To understand the subsurface biosphere, borehole investigation was conducted for 300-m deep granitic rocks at the Mizunami underground research laboratory, Japan. The initial biomass was the highest with the flourish of aerobic H-oxidizing Hydrogenophaga spp., whereas an uncultivated lineage of the phylum Nitrospirae became predominant after three years with decreasing biomass. The common occurrence of many species of Nitrospirae and Chlorobi phyla at the geographically distinct sites and the exclusive detection of their phylogenetically related environmental sequences from deep groundwaters and terrestrial hot springs, suggest that these bacteria are indigenous and potentially adapted to the deep terrestrial subsurface.
Morishita, Yuki; Yamamoto, Seiichi*; Izaki, Kenji; Kaneko, Junichi*; Toi, Kohei*; Tsubota, Yoichi*; Higuchi, Mikio*
Nuclear Instruments and Methods in Physics Research A, 764, p.383 - 386, 2014/11
Times Cited Count：36 Percentile：93.56(Instruments & Instrumentation)Morishita, Yuki; Yamamoto, Seiichi*; Izaki, Kenji; Kaneko, Junichi*; Toi, Kohei*; Tsubota, Yoichi*
Nuclear Instruments and Methods in Physics Research A, 747, p.81 - 86, 2014/05
Times Cited Count：40 Percentile：94.83(Instruments & Instrumentation)Alpha particles are monitored for detecting nuclear fuel material (i.e., plutonium and uranium) at nuclear fuel facilities. In this study, we developed a new alpha-particle imaging system by combining an Si-PM array, which is insensitive to noise, with a Ce-doped Gd
AlGaO
(GAGG) scintillator, and evaluated our developed system's fundamental performance. The scintillator was 0.1-mm thick, and the light guide was 3.0 mm thick. An 
Am source was used for all the measurements. We evaluated the spatial resolution by taking an image of a resolution chart. A 1.6 lp/mm slit was clearly resolved, and the spatial resolution was estimated to be less than 0.6-mm FWHM. The energy resolution was 13% FWHM. A slight distortion was observed in the image, and the uniformity near its center was within 24%. We conclude that our developed alpha-particle imaging system is promising for plutonium detection at nuclear fuel facilities.
; A Ge-nuclear-quadrupole-resonance study under pressureHarada, Atsushi*; Kawasaki, Shinji*; Mukuda, Hidekazu*; Kitaoka, Yoshio*; Haga, Yoshinori; Yamamoto, Etsuji; Onuki, Yoshichika; Ito, Kohei*; Haller, E. E.*; Harima, Hisatomo*
Physical Review B, 75(14), p.140502_1 - 140502_4, 2007/04
Times Cited Count：28 Percentile：72.24(Materials Science, Multidisciplinary)This paper reports that a different type of superconducting order parameter has been realized in the ferromagnetic states in UGe via Ge-nuclear-quadrupole-resonance experiments performed under pressure. Measurements of the nuclear spin-lattice relaxation rate (1/
) have revealed an unconventional nature of superconductivity such that the up-spin band is gapped with line nodes, but the down-spin band remains gapless at the Fermi level. This result is consistent with that of a ferromagnetic spin-pairing model in which Cooper pairs are formed among ferromagnetically polarized electrons. The present experiment has shed light on the possible origin of ferromagnetic superconductivity, which is mediated by ferromagnetic spin-density fluctuations relevant to the first-order transition inside the ferromagnetic states.
; Ge-NQR study under pressureHarada, Atsushi*; Kawasaki, Shinji*; Mukuda, Hidekazu*; Kitaoka, Yoshio*; Haga, Yoshinori; Yamamoto, Etsuji; Onuki, Yoshichika; Ito, Kohei*; Haller, E. E.*; Harima, Hisatomo*
Physica B; Condensed Matter, 378-380, p.963 - 964, 2006/05
Times Cited Count：1 Percentile：6.64(Physics, Condensed Matter)The superconducting characteristics on the itinerant ferromagnetic superconductor UGe have been investigated via the Ge-NQR measurements under pressure (
) near the critical pressure 
where the first-order transition takes place from the low-temperature () and low- ferromagnetic phase (FM2) to high- and high- one (FM1). The measurements of nuclear spin-lattice relaxation rate 
have revealed a power-law like behavior as 
without the coherence peak, whereas at low temperatures, it deviates from the dependence to a -linear like behavior. These results that depend on the pressure are well understood in terms of non-unitary spin-triplet pairing state where the ferromagnetic up-spin band is gapped, but the down-spin band remains gapless at the Fermi level. We will argue an intimate relationship of the onset of SC with FM1 and FM2.
; A Ge-NQR study under pressureHarada, Atsuyuki*; Kawasaki, Shinji*; Kotegawa, Hisashi*; Kitaoka, Yoshio*; Haga, Yoshinori; Yamamoto, Etsuji; Onuki, Yoshichika; Ito, Kohei*; Haller, E. E.*; Harima, Hisatomo*
Journal of the Physical Society of Japan, 74(10), p.2675 - 2678, 2005/10
Times Cited Count：20 Percentile：68.65(Physics, Multidisciplinary)no abstracts in English
Yamamoto, Kohei; Kaji, Naoya; Morimoto, Kazuyuki; Obu, Tomoyuki; Sano, Yuichi; Kashimura, Takao
no journal, ,
no abstracts in English
