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Tamii, Atsushi*; Pellegri, L.*; S
derstrm, P.-A.*; Allard, D.*; Goriely, S.*; Inakura, Tsunenori*; Khan, E.*; Kido, Eiji*; Kimura, Masaaki*; Litvinova, E.*; et al.
European Physical Journal A, 59(9), p.208_1 - 208_21, 2023/09
Times Cited Count：1 Percentile：0.02(Physics, Nuclear)no abstracts in English
Sueyoshi, Tetsuro*; Kotaki, Tetsuya*; Furuki, Yuichi*; Fujiyoshi, Takanori*; Semboshi, Satoshi*; Ozaki, Toshinori*; Sakane, Hitoshi*; Kudo, Masaki*; Yasuda, Kazuhiro*; Ishikawa, Norito
Japanese Journal of Applied Physics, 59(2), p.023001_1 - 023001_7, 2020/02
Times Cited Count：6 Percentile：38.95(Physics, Applied)We show that Xe ion irradiation with 80 MeV to GdBa
Cu
Oy-coated conductors creates different morphologies of columnar defects (CDs) depending on the irradiation angles relative to the c-axis: continuous CDs with a larger diameter are formed for oblique irradiation at 
= 45
, whereas the same ion beam at a different angle ( = 0) induces the formation of discontinuous CDs. The direction-dependent morphologies of CDs significantly affect the angular behavior of the critical current density 
.
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.
Kiriyama, Hiromitsu; Mori, Michiaki; Nakai, Yoshiki; Shimomura, Takuya*; Tanoue, Manabu*; Akutsu, Atsushi; Okada, Hajime; Motomura, Tomohiro*; Kondo, Shuji; Kanazawa, Shuhei; et al.
JAEA-Conf 2008-007, p.13 - 16, 2008/08
One of the main bottlenecks for the applications of ultrashort and ultrahigh-peak power lasers in high-field physics is a temporal contrast of the pulses. In ultrahigh-peak power lasers, a nanosecond background of the amplified spontaneous emission (ASE) is generated at the same time as the femtosecond pulse. This background is mostly generated in the preamplifier (regenerative, multipass amplifier). Even though the contrast level is usually in the range from 10
to 10
, this level is not sufficiently low at relativistic intensities greater than 10
W/cm
to avoid unwanted pre-plasmas generation. We demonstrated a high-contrast, high-peak power laser with optical parametric chirped-pulse amplification (OPCPA). With the use of OPCPA, contrast is enhanced to better than 7
10
in a few picoseconds before the main pulse, which corresponds to an improvement of three to four orders in magnitude compared with conventional systems.
Hayashi, Yukio; Fukumi, Atsushi*; Matsukado, Koji*; Mori, Michiaki; Kotaki, Hideyuki; Kando, Masaki; Chen, L.-M.; Daito, Izuru; Kondo, Shuji; Kanazawa, Shuhei; et al.
Radiation Protection Dosimetry, 121(2), p.99 - 107, 2006/12
Times Cited Count：16 Percentile：70.56(Environmental Sciences)The authors obtain a new equation to estimate the forward component of a photon dose which is generated through the interaction between a target and a short pulse high power laser. As the equation is quite simple, it is useful for calculating the photon dose. The equation shows that the photon dose is proportional to the electron temperature for the range of its temperature 
3 MeV, and proportional to square of the electron temperature for the range of its temperature 
3 MeV. The dose estimated with this method is roughly consistent with the result of Monte Carlo simulation. On someassumptions and corrections, it can reproduce experimental results obtained and the dose result calculated at other laboratories.
Ushigome, Masahiro*; Ide, Shunsuke; Ito, Satoshi*; Jotaki, Eriko*; Mitarai, Osamu*; Shiraiwa, Shunichi*; Suzuki, Takahiro; Takase, Yuichi*; Tanaka, Shigetoshi*; Fujita, Takaaki; et al.
Nuclear Fusion, 46(2), p.207 - 213, 2006/02
Times Cited Count：11 Percentile：37.01(Physics, Fluids & Plasmas)This papaer studies on tokamak plasma start-up completely without central solenoid (CS). On the JT-60 tokamak it is demonstrated that a completely CS-less Ip start-up to 100 kA was achieved even without any null-point by Electron cyclotron range of frequencies (ECRF) and outer PF coil current swing only. Necessary conditions (the EC power, the toroidal field etc.) were clarified. Moreover, it was succeded to maintain Ip = 260kA for 1 sec without CS by NB only. In addition Ip ramp-up by EC and NB only (without LHCD) from 215 to 310kA was achieved. In a high confinement reversed shear discharge, a result suggesting bootstrap over drive was obtained.
Shiraiwa, Shunichi*; Ide, Shunsuke; Ito, Satoshi*; Mitarai, Osamu*; Naito, Osamu; Ozeki, Takahisa; Sakamoto, Yoshiteru; Suzuki, Takahiro; Takase, Yuichi*; Tanaka, Shigetoshi*; et al.
Physical Review Letters, 92(3), p.035001_1 - 035001_4, 2004/01
Times Cited Count：46 Percentile：82.94(Physics, Multidisciplinary)no abstracts in English
Ninomiya, Hiromasa; Kitsunezaki, Akio; Shimizu, Masatsugu; Kuriyama, Masaaki; JT-60 Team; Kimura, Haruyuki; Kawashima, Hisato; Tsuzuki, Kazuhiro; Sato, Masayasu; Isei, Nobuaki; et al.
Fusion Science and Technology, 42(1), p.7 - 31, 2002/07
Times Cited Count：13 Percentile：27.27(Nuclear Science & Technology)In order to establish scientific basis for the sustainment of highly integrated performance required in the advanced steady-state operation, JT-60U has been optimizing the discharge control scenarios of improved confinement plasmas and expanding the operation regions. Promising results toward the steady-state tokamak were obtained. The detail of such results is reported. JFT-2M has performed advanced and basic research for the development of high performance tokamak plasma as well as the structural material for a fusion reactor. The toroidal ripple reduction with ferritic steel plates outside the vacuum vessel was successfully demonstrated. No adverse effects were observed in the pre-testing on compatibility between ferritic steel plates, covering ~20% of the inside wall of the vacuum vessel, and plasma. The results of TRIAM-1M is also reported.
Hirose, Jiro*; Muramatsu, Ken; Okumura, Toshihiko*; Taki, Satoshi*
JAERI-Research 2002-009, 220 Pages, 2002/03
JAERI-Research-2002-009.pdf:13.31MB
This report presents procedures for the determination of Scenario Earthquakes for seismic design based on Probabilistic Seismic Hazard Analysis (PSHA). Recently PSHA was recognized as an important basis to identify dominant earthquakes predicted to threaten the site in future. The identified earthquakes are called Probability-Based Scenario Earthquakes (PBSEs). The concept of PBSEs originates from the studies of US NRC and Ishikawa & Kameda. The objective of this study is to formulate the procedures to determine the PBSEs and, through this application, to demonstrate the feasibility of the application to seismic design. This report consists of three parts, namely, procedures to compile analytical conditions for PBSEs, an assessment to determine PBSEs for a model site using the Ishikawa's concept and examination of uncertainty involved in analytical conditions. The results imply that the procedures based on the Ishikawa's concept is a useful evaluation technique to determine scenario earthquakes for seismic design considering uncertainty involved in analytical conditions.
Hirose, Jiro*; Muramatsu, Ken; Okumura, Toshihiko*; Taki, Satoshi*; Takada, Tsuyoshi*
Proceedings of 5th International Conference on Probabilistic Safety Assessment and Management (PSAM-5), p.1383 - 1390, 2000/00
no abstracts in English
Kiriyama, Hiromitsu; Mori, Michiaki; Daito, Izuru; Kotaki, Hideyuki; Nakai, Yoshiki; Shimomura, Takuya*; Tanoue, Manabu*; Akutsu, Atsushi; Okada, Hajime; Motomura, Tomohiro*; et al.
no journal, ,
We report on a high-peak-power, high-contrast laser system, which combines both conventional Ti:sapphire chirped-pulse amplification and optical parametric chirped-pulse amplification (OPCPA) techniques for use in experiments where relativistic effects dominate the physics. The stretched pulses are amplified in a 3-stage Type-I Bata-Barium Borate OPCPA to an energy level of 10 mJ with an amplification gain of 10
. The output pulses are then amplified in the subsequent Ti:sapphire amplifiers to an energy level of 2.9 J. Pulse compression down to 19 fs duration achieved after amplification indicates a peak power of 80 TW. The pre-pulse contrast is enhanced to better than 
within a few picoseconds before the main pulse. The thermal focal length of about 4 km is obtained.
Kiriyama, Hiromitsu; Mori, Michiaki; Nakai, Yoshiki; Shimomura, Takuya*; Tanoue, Manabu*; Akutsu, Atsushi; Okada, Hajime; Motomura, Tomohiro*; Kondo, Shuji; Kanazawa, Shuhei; et al.
no journal, ,
no abstracts in English
Kiriyama, Hiromitsu; Mori, Michiaki; Nakai, Yoshiki; Shimomura, Takuya; Tanoue, Manabu*; Okada, Hajime; Kondo, Shuji; Kanazawa, Shuhei; Sagisaka, Akito; Daito, Izuru; et al.
no journal, ,
We have demonstrated over 30 J broadband output energy based on optical parametric chirped-pulse amplification (OPCPA) and Ti:sapphire chirped-pulse amplification (CPA), indicating potential for peak power of 500 TW with extremely high temporal contrast.
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
to 10
has been obtained with a near-perfect flat-topped spatial-profile of filling factor 
80%. We also present a compact, high-intensity OPCPA/Yb:YAG hybrid laser system that generates 100 mJ output energy with a temporal contrast of better than 10
and good spatial beam quality.
Faenov, A.*; Pikuz, T.; Fukuda, Yuji; Jinno, Satoshi; Sakaki, Hironao; Kanasaki, Masato; Kotaki, Hideyuki; Bulanov, S. V.; Pirozhkov, A. S.; Yogo, Akifumi; et al.
no journal, ,
