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Ezure, Toshiki; Akimoto, Yuta; Matsushita, Kentaro; Tanaka, Masaaki
Dai-27-Kai Doryoku, Enerugi Gijutsu Shimpojiumu Koen Rombunshu (Internet), 5 Pages, 2023/09
In hot plenums of sodium-cooled fast reactors, restriction of cover gas entrainment caused by vortex dimples on the free surface is an important thermal-hydraulic issue. For this reason, the authors have developed an evaluation method of gas entrainment with an evaluation tool named, StreamViewer. In this study, evaluation using StreamViewer was applied to a water experiment having a simplified hot pool geometry aiming at the validation of the evaluation method toward the application to the evaluation of a pool-type sodium cooled fast reactor. In StreamViewer, the three-dimensional distribution of pressure decrease along the vortex center line was calculated from the velocity distribution obtained by CFD analyses, and the free surface dimple depth was obtained from the hydraulic balance with the pressure distribution and the cover gas pressure. As the results, it was confirmed that the onset of gas entrainment could be predicted appropriately based on the above-mentioned calculation method.
Kakimoto, Kazuo*; Takada, Saki*; Ota, Hiroto*; Hayaguchi, Yuya*; Hagihara, Masato; Torii, Shuki*; Kamiyama, Takashi*; Mitamura, Hiroyuki*; Tokunaga, Masashi*; Hatakeyama, Atsushi*; et al.
Journal of the Physical Society of Japan, 91(5), p.054704_1 - 054704_7, 2022/05
Times Cited Count:1 Percentile:28(Physics, Multidisciplinary)Muramatsu, Haruka*; Hayashi, Tasuku*; Yuasa, Naoki*; Konno, Ryohei*; Yamaguchi, Atsushi*; Mitsuda, Kazuhisa*; Yamasaki, Noriko*; Maehata, Keisuke*; Kikunaga, Hidetoshi*; Takimoto, Misaki; et al.
Journal of Low Temperature Physics, 200(5-6), p.452 - 460, 2020/09
Times Cited Count:1 Percentile:6.04(Physics, Applied)Yamaguchi, Atsushi*; Muramatsu, Haruka*; Hayashi, Tasuku*; Yuasa, Naoki*; Nakamura, Keisuke; Takimoto, Misaki; Haba, Hiromitsu*; Konashi, Kenji*; Watanabe, Makoto*; Kikunaga, Hidetoshi*; et al.
Physical Review Letters, 123(22), p.222501_1 - 222501_6, 2019/11
Times Cited Count:36 Percentile:89.11(Physics, Multidisciplinary)Hasegawa, Noboru; Nishikino, Masaharu; Tomita, Takuro*; Onishi, Naofumi*; Ito, Atsushi*; Eyama, Tsuyoshi*; Kakimoto, Naoya*; Izutsu, Rui*; Minami, Yasuo*; Baba, Motoyoshi*; et al.
X-Ray Lasers and Coherent X-Ray Sources; Development and Applications XI (Proceedings of SPIE, Vol.9589), p.95890A_1 - 95890A_8, 2015/09
Times Cited Count:1 Percentile:55.52(Optics)We have improved a soft X-ray laser (SXRL) interferometer synchronized with a Ti:Sapphire laser pulse to observe the single-shot imaging of the nano-scaled structure dynamics of the laser induced materials. By the precise imaging optics and double time fiducial system having been installed, the lateral resolution on the sample surface and the precision of the temporal synchronization between the SXRL and Ti:Sapphire laser pulses were improved to be 700 nm and 2 ps, respectively. By using this system, the initial stage (before 200 ps) of the ablation process of the Pt surface pumped by 80 fs Ti:Sapphire laser pulse was observed by the comparison between the soft X-ray reflective image and interferogram. We have succeeded in the direct observation of the unique ablation process around the ablation threshold such as the rapid increase of the surface roughness and surface vibration.
Hasegawa, Noboru; Tomita, Takuro*; Nishikino, Masaharu; Eyama, Tsuyoshi*; Kakimoto, Naoya*; Minami, Yasuo*; Baba, Motoyoshi*; Onishi, Naofumi*; Ito, Atsushi*; Kawachi, Tetsuya; et al.
JAEA-Conf 2015-001, p.17 - 20, 2015/07
We have succeeded in simultaneous observation of the ablation front and the expansion front with thin filmy structure in the femto-second laser ablation process of a gold target by using the 13.9 nm soft X-ray probe (incident angle to the sample 70 deg) with soft X-ray interferometer. The dependence on the laser local fluence and materials was obtained by the comparison between gold and tungsten.
Nishikino, Masaharu; Hasegawa, Noboru; Tomita, Takuro*; Eyama, Tsuyoshi*; Kakimoto, Naoya*; Onishi, Naofumi*; Ito, Atsushi*; Baba, Motoyoshi*; Minami, Yasuo*; Kawachi, Tetsuya; et al.
Reza Gakkai Dai-471-Kai Kenkyukai Hokoku; Tanhacho Ryoshi Bimu Hassei To Sono Oyo, p.9 - 12, 2014/12
no abstracts in English
Hashimoto, Makoto*; Yoshida, Teppei*; Tanaka, Kiyohisa*; Fujimori, Atsushi*; Okusawa, Makoto*; Wakimoto, Shuichi; Yamada, Kazuyoshi*; Kakeshita, Teruhisa*; Eisaki, Hiroshi*; Uchida, Shinichi*
Physical Review B, 79(14), p.140502_1 - 140502_4, 2009/04
Times Cited Count:14 Percentile:52.28(Materials Science, Multidisciplinary)Izawa, Yasukazu*; Nishihara, Katsunobu*; Tanuma, Hajime*; Sasaki, Akira; Murakami, Masakatsu*; Sunahara, Atsushi*; Nishimura, Hiroaki*; Fujioka, Shinsuke*; Aota, Tatsuya*; Shimada, Yoshinori*; et al.
Journal of Physics; Conference Series, 112, p.042047_1 - 042047_4, 2008/00
Times Cited Count:8 Percentile:93.57(Physics, Fluids & Plasmas)In the development of a high power EUV source used in the EUV lithography system, we have been constructed EUV database of laser-produced tin plasma by the theoretical and experimental studies. On the basis of our understanding, the optimum conditions of lasers and plasmas were clarified, and we proposed the guidelines of laser plasma to obtain clean, efficient and high power EUV source for the practical EUV lithography system. In parallel to such studies, novel targets and high power laser system to generate the optimized EUV source plasma have been developed.
Hashimoto, Makoto*; Tanaka, Kiyohisa*; Yoshida, Teppei*; Fujimori, Atsushi*; Okusawa, Makoto*; Wakimoto, Shuichi; Yamada, Kazuyoshi*; Kakeshita, Teruhisa*; Eisaki, Hiroshi*; Uchida, Shinichi*
Physica C, 460-462(2), p.884 - 885, 2007/09
Times Cited Count:3 Percentile:17.87(Physics, Applied)In the high- research, relationship between the pseudogap and the superconducting gap has been an important issue. We have performed a detailed temperature-dependent angle-integrated photoemission study of lightly-doped to heavily-overdoped LaSrCuO and oxygen-doped LaCuO. We found that, while the magnitude of the pseudogap increased with decreasing doping, that of the superconducting gap did not increase. This behavior can be explained if the superconducting gap opens only on the Fermi arc around the node (0,0)-(,) whereas the pseudogap opens primarily around (,0).
Hashimoto, Makoto*; Yoshida, Teppei*; Tanaka, Kiyohisa*; Fujimori, Atsushi*; Okusawa, Makoto*; Wakimoto, Shuichi; Yamada, Kazuyoshi*; Kakeshita, Teruhisa*; Eisaki, Hiroshi*; Uchida, Shinichi*
Physical Review B, 75(14), p.140503_1 - 140503_4, 2007/04
Times Cited Count:66 Percentile:88.61(Materials Science, Multidisciplinary)We have performed a temperature-dependent angle-integrated photoemission study of LaSrCuO covering from lightly doped to heavily overdoped regions and oxygen -doped LaCuO. The superconducting gap energy was found to remain small for decreasing hole concentration while the pseudogap energy and temperature increase. The different behaviors of the superconducting gap and the pseudogap can be explained if the superconducting gap opens only on the Fermi arc around the nodal (0,0)- direction while the pseudogap opens around . The results suggest that the pseudogap and the superconducting gap have different microscopic origins.
Kaminaga, Masanori; Sasaki, Shinobu; Haga, Katsuhiro; Aso, Tomokazu; Kinoshita, Hidetaka; Kogawa, Hiroyuki; Akimoto, Atsushi*; Adachi, Junichi*; Hino, Ryutaro
JAERI-Tech 2000-060, 37 Pages, 2000/11
no abstracts in English
Nishikino, Masaharu; Hasegawa, Noboru; Tomita, Takuro*; Eyama, Tsuyoshi*; Kakimoto, Naoya*; Hatomi, Daiki*; Onishi, Naofumi*; Ito, Atsushi*; Kawachi, Tetsuya; Yamagiwa, Mitsuru; et al.
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Nishikino, Masaharu; Hasegawa, Noboru; Tomita, Takuro*; Eyama, Tsuyoshi*; Kakimoto, Naoya*; Onishi, Naofumi*; Hatomi, Daiki*; Ito, Atsushi*; Minami, Yasuo*; Takei, Ryota*; et al.
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Yamagiwa, Mitsuru; Hasegawa, Noboru; Nishikino, Masaharu; Tomita, Takuro*; Eyama, Tsuyoshi*; Kakimoto, Naoya*; Onishi, Naofumi*; Hatomi, Daiki*; Ito, Atsushi*; Minami, Yasuo*; et al.
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Hasegawa, Noboru; Nishikino, Masaharu; Tomita, Takuro*; Eyama, Tsuyoshi*; Kakimoto, Naoya*; Hatomi, Daiki*; Onishi, Naofumi*; Ito, Atsushi*; Minami, Yasuo*; Takei, Ryota*; et al.
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We have observed the temporal evolution of the femto-second laser irradiated metal surface by using the soft X-ray laser probe at the wavelength of 13.9 nm. We have succeeded to obtain the temporal evolution of the ablation front from the result of the soft X-ray reflective imaging and interferogram. We will report about "the Newton's ring generated between the ablation front and the metal surface" and "the ablation front dynamics observed by the soft X-ray shadow graph".
Nishikino, Masaharu; Hasegawa, Noboru; Eyama, Tsuyoshi*; Kakimoto, Naoya*; Tomita, Takuro*; Hatomi, Daiki*; Onishi, Naofumi*; Ito, Atsushi*; Minami, Yasuo*; Baba, Motoyoshi*; et al.
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The dynamical process of laser-induced surface modification such as the laser ablation comes to attract much attention for the micro processing by the ultra-short laser pulse. In order to observe the surface morphological change during the fs laser ablation process with a weakly excitation, we have developed soft X-ray interferometer and reflectometer system. Weakly excited ablation processes of the gold (Au) films are investigated by using single shot pump and probe imaging technique, using a Ti:Sapphire laser pulse with the duration of 80 fs pulse at a central wavelength of 795 nm for the pumping of ablation and the laser-driven soft X-ray laser at the wavelength of 13.9 nm for the probe. We discuss the scenario of the weakly excited femtosecond laser ablation of the gold surface. The numerical simulation study of the fs laser ablation process is underway by using a parallel molecular dynamics code.
Nishikino, Masaharu; Hasegawa, Noboru; Tomita, Takuro*; Eyama, Tsuyoshi*; Kakimoto, Naoya*; Onishi, Naofumi*; Ito, Atsushi*; Baba, Motoyoshi*; Minami, Yasuo*; Kawachi, Tetsuya; et al.
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Nishikino, Masaharu; Hasegawa, Noboru; Tomita, Takuro*; Eyama, Tsuyoshi*; Kakimoto, Naoya*; Onishi, Naofumi*; Ito, Atsushi*; Kawachi, Tetsuya; Yamagiwa, Mitsuru; Suemoto, Toru
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no abstracts in English
Takimoto, Misaki; Yamazaki, Takumi; Imahashi, Atsushi; Hoshi, Katsuya; Kawasaki, Takashi; Yoshida, Tadayoshi; Takada, Chie; Tsujimura, Norio; Okada, Kazuhiko; Ishikawa, Hisashi
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no abstracts in English