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Journal Articles

Intrinsic 2D ferromagnetism in V$$_{5}$$Se$$_{8}$$ epitaxial thin films

Nakano, Masaki*; Wang, Y.*; Yoshida, Satoshi*; Matsuoka, Hideki*; Majima, Yuki*; Ikeda, Keisuke*; Hirata, Yasuyuki*; Takeda, Yukiharu; Wadachi, Hiroki*; Kohama, Yoshimitsu*; et al.

Nano Letters, 19(12), p.8806 - 8810, 2019/12

 Times Cited Count:31 Percentile:90.57(Chemistry, Multidisciplinary)

Journal Articles

High power laser developments with femtosecond to nanosecond pulse durations for laser shock science and engineering

Kiriyama, Hiromitsu; Mori, Michiaki; Suzuki, Masayuki*; Daito, Izuru*; Okada, Hajime; Ochi, Yoshihiro; Tanaka, Momoko; Sato, Masatoshi*; Tamaoki, Yoshinori*; Yoshii, Takehiro*; et al.

Reza Kenkyu, 42(6), p.441 - 447, 2014/06

We describe three specific high power laser systems that are being developed in our laboratory for many applications in high field science, nonlinear optics and material processing. We report on a femtosecond petawatt-class Ti:sapphire chirped-pulse amplification laser system that can produce a pulse energy of 20 J of 40 fs pulse duration, a picosecond high intensity Yb:YAG chirped-pulse amplification laser system that can generate a pulse energy of 100 mJ of 0.5 ps pulse duration, and a nanosecond high repetition rate Nd:YAG laser system that can provide an average power of 360 W with a pulse duration of 30 ns delivered at a 1 kHz repetition rate. We discuss the basic design aspects and present the results from our experimental investigations of these laser systems.

Journal Articles

Ultra-intense, high spatio-temporal quality petawatt-class laser system and applications

Kiriyama, Hiromitsu; Shimomura, Takuya; Mori, Michiaki; Nakai, Yoshiki*; Tanoue, Manabu; Kondo, Shuji; Kanazawa, Shuhei; Pirozhkov, A. S.; Esirkepov, T. Z.; Hayashi, Yukio; et al.

Applied Sciences (Internet), 3(1), p.214 - 250, 2013/03

 Times Cited Count:15 Percentile:56.25(Chemistry, Multidisciplinary)

This paper reviews techniques for improving the temporal contrast and spatial beam quality in an ultra-intense laser system that is based on chirped-pulse amplification (CPA). We describe the design, performance, and characterization of our laser system, which has the potential for achieving a peak power of 600 TW. We also describe applications of the laser system in the relativistically dominant regime of laser-matter interactions and discuss a compact, high efficiency diode-pumped laser system.

Journal Articles

Development of a compact high-spatiotemporal-quality Yb:YAG thin-disk laser system using an optical parametric preamplifier

Kiriyama, Hiromitsu; Suzuki, Masayuki*; Daito, Izuru; Okada, Hajime; Ochi, Yoshihiro; Sato, Masatoshi*; Tamaoki, Yoshinori*; Yoshii, Takehiro*; Maeda, Junya*; Matsuoka, Shinichi*; et al.

Reza Kenkyu, 40(2), p.143 - 145, 2012/02

We demonstrate a compact, high-spatiotemporal-quality, high-intensity diode-pumped Yb:YAG thin-disk chirped-pulse amplification (CPA) laser system that incorporates a nonlinear preamplifier based on optical parametric chirped-pulse amplification (OPCPA). The stretched pulses are amplified in the OPCPA preamplifier and the following Yb:YAG main amplifier to $$sim$$100 mJ at 10 Hz. The broadband amplified beam quality of 1.1 (horizontal direction) and 1.4 (vertical direction) times diffraction limited and pulse compression down to 470 fs with contrast of better than 10$$^{-8}$$ have been achieved successfully.

JAEA Reports

Establishment of advanced integration technology for site characterization of deep geological repository; Development of information synthesis and interpretation system; Annual report 2007 (Contract research)

Osawa, Hideaki; Ota, Kunio; Hama, Katsuhiro; Sawada, Atsushi; Takeuchi, Shinji; Amano, Kenji; Saegusa, Hiromitsu; Matsuoka, Toshiyuki; Miyamoto, Tetsuo; Toyoda, Gakuji; et al.

JAEA-Research 2008-085, 742 Pages, 2008/11

JAEA-Research-2008-085-1.pdf:26.22MB
JAEA-Research-2008-085-2.pdf:16.64MB
JAEA-Research-2008-085-3.pdf:28.27MB

This report shows the results the project for the establishment of comprehensive site characterization technology, entrusted from Natural Resources and Energy Agency, Ministry of Economy, Trade and Industry Natural Resources and Energy Agency in 2007.

Journal Articles

Experimental progress on zonal flow physics in toroidal plasmas

Fujisawa, Akihide*; Ido, Takeshi*; Shimizu, Akihiro*; Okamura, Shoichi*; Matsuoka, Keisuke*; Iguchi, Harukazu*; Hamada, Yasuji*; Nakano, Haruhisa*; Oshima, Shinsuke*; Ito, Kimitaka*; et al.

Nuclear Fusion, 47(10), p.S718 - S726, 2007/10

 Times Cited Count:97 Percentile:95.74(Physics, Fluids & Plasmas)

Present status of experiments on zonal flows is overviewed. Innovative use of modern diagnostics has revealed the existence of zonal flows, their spatio-temporal characteristics, their relationship with turbulence, and their effects on confinement. Particularly a number of observations have been accumulated on the oscillatory branch of the zonal flow, dubbed as geodesic acoustic modes suggesting necessity of theories to give their proper description. Several new methods have elucidated the zonal flow generation processes from the turbulence. Further investigation of relationship between the zonal flows and confinement is strongly encouraged as cross-device activity.

Journal Articles

Experimental progress on zonal flow physics in toroidal plasmas

Fujisawa, Akihide*; Ido, Takeshi*; Shimizu, Akihiro*; Okamura, Shoichi*; Matsuoka, Keisuke*; Hamada, Yasuji*; Hoshino, Katsumichi; Nagashima, Yoshihiko*; Shinohara, Koji; Nakano, Haruhisa*; et al.

Proceedings of 21st IAEA Fusion Energy Conference (FEC 2006) (CD-ROM), 12 Pages, 2007/03

Present status of experiments on zonal flows is overviewed. Innovative use of traditional and modern diagnostics has revealed unambiguously the existense of the zonal flows, their spatio-temporal caracteristics, their relationship with turbulence, and their effects on confinement. Particularly, a number of observations have been accumulated on the oscillatory branch of zonal flows, dubbed geodesic acoustic modes, suggesting necessity of theories to give their proper description. Furthur investigation of relationship between zonal flows and confinement is strongly encouraged as cross-device activity.

Journal Articles

Studies of fast-ion transport induced by energetic particle modes using fast-particle diagnostics with high time resolution in CHS

Isobe, Mitsutaka*; Toi, Kazuo*; Matsushita, Hiroyuki*; Goto, Kazuyuki*; Suzuki, Chihiro*; Nagaoka, Kenichi*; Nakajima, Noriyoshi*; Yamamoto, Satoshi*; Murakami, Sadayoshi*; Shimizu, Akihiro*; et al.

Nuclear Fusion, 46(10), p.S918 - S925, 2006/10

 Times Cited Count:27 Percentile:68.17(Physics, Fluids & Plasmas)

no abstracts in English

Journal Articles

Experimental study of nonlinear processes in edge turbulence of toroidal plasmas

Nagashima, Yoshihiko*; Hoshino, Katsumichi; Nagaoka, Kenichi*; Shinohara, Koji; Fujisawa, Akihide*; Uehara, Kazuya; Kusama, Yoshinori; Ida, Katsumi*; Yoshimura, Yasuo*; Okamura, Shoichi*; et al.

Plasma and Fusion Research (Internet), 1(9), p.041_1 - 041_15, 2006/09

Nonlinear processes between meso-scale structures and turbulent fluctuations in the edge region of the toroidal plasmas were studied using the bispectrum analysis. In the JFT-2M tokamak, divertor plasmas were investigated as well as the limiter plasmas, and the amplitude and phase of the bispectrum function of the potential fluctuation were found to be consistent with an analysis of the drift wave-zonal flow system. In the CHS machine, the edge plasmas during the H-mode were investigated. It was found that the edge potential begins to decrease before the decrease of the intensity of the deuterium line (by about 30ms), and the edge fluctuations are found to be composed of low frequency MHD fluctuations, drift wave like broad band electrostatic fluctuations and high frequency electromagnetic fluctuations. Nonlinear coupling between the MHD fluctuations and the electrostatic fluctuations or the electromagnetic fluctuations were found for the first time.

Journal Articles

Observation of nonlinear processes between coherent fluctuations and turbulent fluctuations in the edge regions of JFT-2M and CHS

Nagashima, Yoshihiko*; Ito, Kimitaka*; Ito, Sanae*; Fujisawa, Akihide*; Hoshino, Katsumichi; Nagaoka, Kenichi*; Ejiri, Akira*; Takase, Yuichi*; Yagi, Masatoshi*; Shinohara, Koji; et al.

Europhysics Conference Abstracts (CD-ROM), 30I, 4 Pages, 2006/00

The results of the analyses of nonlinear processes in the plasma in JFT-2M tokamak and CHS machine are reported. In both machines, the measurements of the fluctuations were done by electrostatic probes. The obtained bicoherence and biphase from the potential data in JFT-2M were found to be close to the values obtained from a theoretical model of the interaction of the zonal flow and the drift wave turbulence. Therefore the experimentally obtained nonlinear interaction is considered to be that interaction of the zonal flow and the drift wave turbulence. By the analysis of the CHS H-mode plasma, a marked nonlinear interaction was found between a characteristic MHD magnetic fluctuation and density turbulence. By analysing the cross bispectrum of the density fluctuation and the potential fluctuation, it was found that the fluctuating particle flux is affected by the MHD oscillation. As stated above, we progressed in the investigation of the nonlinear processes of the edge plasmas.

Oral presentation

Experimental study of nonlinear processes in edge turbulence of toroidal plasmas

Nagashima, Yoshihiko*; Hoshino, Katsumichi; Shinohara, Koji; Uehara, Kazuya; Kusama, Yoshinori; Nagaoka, Kenichi*; Fujisawa, Akihide*; Ida, Katsumi*; Yoshimura, Yasuo*; Okamura, Shoichi*; et al.

no journal, , 

We present an invited talk on the experimental study of the nonlinear interaction processes of the edge plasma turbulence studied in the JFT-2M tokamak machine of JAEA and in the CHS helical machine of the NIFS. We made a progress in understanding the nonlinear interaction of the drift wave turbulence and the zonal flow by measuring the potential fluctuations and density fluctuations by the measurement of the electrostatic probes. We found that the measured indices such as the bicoherence or the biphase are consistent with the results of a theoretical study of the drift-wave-zonal-flow system for the first time. We also made the convergence characteristic of these indices clear against the realization numbers for the first time. The study progresses the understanding of the plasma turbulence and structural formation in the plasma, and the results contributes much to the understanding of the transport process in the plasma.

Oral presentation

Information Synthesis and Interpretation System (ISIS), 2; Method for geological environmental modeling and establishment of its expert system (cases of geological and groundwater flow modeling)

Semba, Takeshi; Saegusa, Hiromitsu; Matsuoka, Toshiyuki; Maekawa, Keisuke; Amano, Kenji; Andersson, J.*

no journal, , 

In order to identify and prioritize key issues for further investigations, it is important to evaluate the impact of uncertainties in the geological environment model. A plan for site characterization should be made based on the result of modeling of geological environment. In this study, the work-flow of the geological environment model has been summarized based on the technical know-how accumulating from Mizunami Underground Research Laboratory Project and Horonobe Underground Research Laboratory Project. The decision-making process on the modeling has been also summarized.

Oral presentation

Current status of development of next-generation Information Synthesis and Interpretation System (ISIS), 2; Development of expert system for geological environmental modeling

Saegusa, Hiromitsu; Matsuoka, Toshiyuki; Maekawa, Keisuke; Amano, Kenji; Takeuchi, Shinji; Semba, Takeshi

no journal, , 

In this study, the work-flows of (1) the setting of area for modeling of geological environment, (2) geological modeling and (3) groundwater flow modeling, which are to be used for planning of site characterization, have been summarized based on the technical know-how accumulating from Mizunami Underground Research Laboratory Project and Horonobe Underground Research Laboratory Project. The decision-making process on the modeling has been also summarized, and expert systems for the modeling have been developed.

Oral presentation

High-spatiotemporal-quality high-intensity laser system

Kiriyama, Hiromitsu; Mori, Michiaki; Shimomura, Takuya; Nakai, Yoshiki*; Tanoue, Manabu*; Sasao, Hajime*; Kondo, Shuji; Kanazawa, Shuhei; Ochi, Yoshihiro; Tanaka, Momoko; et al.

no journal, , 

We report on a femtosecond high-intensity OPCPA/Ti:sapphire hybrid laser system that produces more than 30 J broadband output energy, indicating the potential for achieving petawatt-class peak powers. High temporal-contrast of 10$$^{-10}$$ to 10$$^{-11}$$ has been obtained with a near-perfect flat-topped spatial-profile of filling factor $$sim$$80%. We also present a compact, high-intensity OPCPA/Yb:YAG hybrid laser system that generates $$sim$$100 mJ output energy with a temporal contrast of better than 10$$^{-8}$$ and good spatial beam quality.

Oral presentation

Development of a high-contrast, high-beam quality, high-intensity laser

Kiriyama, Hiromitsu; Mori, Michiaki; Shimomura, Takuya; Tanoue, Manabu; Kondo, Shuji; Kanazawa, Shuhei; Daito, Izuru; Suzuki, Masayuki*; Okada, Hajime; Ochi, Yoshihiro; et al.

no journal, , 

We describe two specific high intensity laser systems that are being developed in our laboratory for many applications such as high field science, nonlinear optics. We report on an ultra-high intensity petawatt-class Ti:sapphire chirped-pulse amplification laser system that can produce a pulse energy of $$sim$$ 18 J with $$sim$$ 30 fs pulse duration for studying extremely high intensity laser matter interaction process and a small-scaled Yb:YAG chirped-pulse amplification laser system that can generate a pulse energy of $$sim$$ 100 m J of $$sim$$ 500 fs pulse duration for compact, high efficiency, high repetition system. We discuss the basic design aspects and present the results from our experimental investigations of these laser systems.

15 (Records 1-15 displayed on this page)
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