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Yoshino, Ryuji
Nuclear Fusion, 45(11), p.1232 - 1246, 2005/11
Times Cited Count：44 Percentile：76.44(Physics, Fluids & Plasmas)Prediction of major disruptions observed at the 
-limit for tokamak plasmas has been investigated in JT-60U with developing neural networks. A sub-neural network is trained to output a value of the 
limit every 2 ms. The target limit is artificially set by the operator in the first step training and is modified in the second step training using the output limit from the trained network. To improve the prediction performance further, the difference between the estimated limit and the measured and the other 11 parameters are inputted to a main neural network to calculate the stability level. Major disruptions have been predicted with a prediction success rate of 80% at 10 ms prior to the disruption while the false alarm rate is lower than 4%. This 80% is much higher than about 10% previously obtained. A prediction success rate of 90% has been also obtained with a false alarm rate of 12% at 10 ms prior to the disruption. This 12% is about a half of previously obtained one.
Kawano, Yasunori; Nakano, Tomohide; Asakura, Nobuyuki; Tamai, Hiroshi; Isayama, Akihiko; Kondoh, Takashi; Hatae, Takaki; Takenaga, Hidenobu; Ide, Shunsuke
Purazuma, Kaku Yugo Gakkai-Shi, 81(10), p.743 - 744, 2005/10
Electron density of post-disruption runaway plasmas in JT-60U has been measured by the tangential CO
laser interferometer. Increases in electron density after the first drop of runaway plasma current have been observed during a fast termination phase of the runaway plasma. At the second current drop, an increase in electron density with multiple spikes or oscillation with the period of 1 ms has been found. It is suggested that the increased electron density seems to take part in the shorter current decay time after the second current drop.
Bakhtiari, M.; Kramer, G. J.*; Takechi, Manabu; Tamai, Hiroshi; Miura, Yukitoshi; Kusama, Yoshinori; Kamada, Yutaka
Physical Review Letters, 94(21), p.215003_1 - 215003_4, 2005/06
Times Cited Count：58 Percentile：85.65(Physics, Multidisciplinary)Bremsstrahlung radiation of runaway electrons is found to be an energy limit for runaway electrons in tokamaks. The minimum and maximum energy of runaway electron beams is shown to be limited by collisions and Bremsstrahlung radiation, respectively. It is also found that a massive injection of a high-Z gas such as Xenon can terminate a disruption-generated runaway current before the runaway electrons hit the walls.
Owaki, Hirokazu; Sugihara, Masayoshi; Kawano, Yasunori; Lukash, V. V.*; Khayrutdinov, R. R.*; Zhogolev, V.*; Ozeki, Takahisa; Hatayama, Akiyoshi*
Europhysics Conference Abstracts (CD-ROM), 29C, 4 Pages, 2005/00
no abstracts in English
Yoshino, Ryuji
Nuclear Fusion, 43(12), p.1771 - 1786, 2003/12
Times Cited Count：65 Percentile：85.26(Physics, Fluids & Plasmas)no abstracts in English
Sugihara, Masayoshi; Lukash, V.*; Kawano, Yasunori; Yoshino, Ryuji; Gribov, Y.*; Khayrutdinov, R.*; Miki, Nobuharu*; Omori, Junji*; Shimada, Michiya
Proceedings of 30th EPS Conference on Controlled Fusion and Plasma Physics (CD-ROM), 4 Pages, 2003/07
We examine plasma behaviours during plasma disruptions in detail in JT-60U and other tokamaks to derive appropriate physics guidelines for the behaviours. Their interpretations and their extrapolations to ITER are incorporated into the DINA code, which solves plasma transport and 2D free boundary plasma equilibrium simultaneously with circuit equations for the vacuum vessel and the PF coils. Sensitivity of the plasma behaviours and their impact on the EM force during disruptions due to the range of variation and uncertainty of the experimental data are examined.
Sugihara, Masayoshi; Lukash, V.*; Kawano, Yasunori; Yoshino, Ryuji; Gribov, Y.*; Khayrutdinov, R.*; Miki, Nobuharu*; Omori, Junji*; Shimada, Michiya
Purazuma, Kaku Yugo Gakkai-Shi, 79(7), p.706 - 712, 2003/07
The time dependence of the current decay during the current quench phase of disruptions, which can significantly influence the electro-magnetic force on the in-vessel components due to the induced eddy currents, is investigated using data obtained in JT-60U experiments in order to derive a relevant physics guideline for the predictive simulations of disruptions in ITER. It is shown that an exponential decay can fit the time dependence of current quench for discharges with large quench rate (fast current quench). On the other hand, for discharges with smaller quench rate (slow current quench), a linear decay can fit the time dependence of current quench better than exponential.
Nakamura, Yukiharu; Pautasso, G.*; Gruber, O.*; Jardin, S. C.*
Plasma Physics and Controlled Fusion, 44(8), p.1471 - 1481, 2002/08
Times Cited Count：14 Percentile：41.12(Physics, Fluids & Plasmas)no abstracts in English
Nakamura, Yukiharu; Yoshino, Ryuji; Granetz, R. S.*; Pautasso, G.*; Gruber, O.*; Jardin, S. C.*
Purazuma, Kaku Yugo Gakkai-Shi, 78(4), p.347 - 355, 2002/04
no abstracts in English
Nakamura, Yukiharu
Purazuma, Kaku Yugo Gakkai-Shi, 77(9), p.843 - 856, 2001/09
no abstracts in English
Yoshino, Ryuji
Purazuma, Kaku Yugo Gakkai-Shi, 75(12), p.1337 - 1374, 1999/12
no abstracts in English
; Ishii, Yasutomo; ; Tokuda, Shinji; Ozeki, Takahisa; S.Hudson*; Kishimoto, Yasuaki
Chinese Physics Letters, 362, p.83 - 84, 1999/09
no abstracts in English
Neyatani, Yuzuru; Nakamura, Yukiharu; Yoshino, Ryuji; Hatae, Takaki; JT-60 Team
Fusion Energy 1998, p.859 - 862, 1998/10
no abstracts in English
Yoshino, Ryuji; Kondoh, Takashi; Neyatani, Yuzuru; Itami, Kiyoshi; Kawano, Yasunori; Isei, Nobuaki
Plasma Physics and Controlled Fusion, 39(2), p.313 - 332, 1997/02
Times Cited Count：103 Percentile：92.87(Physics, Fluids & Plasmas)no abstracts in English
Koizumi, Koichi; Yamazaki, Kozo*
Purazuma, Kaku Yugo Gakkai-Shi, 72(12), p.1352 - 1361, 1996/12
no abstracts in English
Nakamura, Yukiharu; Yoshino, Ryuji; N.Pomphrey*; S.C.Jardin*
Journal of Nuclear Science and Technology, 33(8), p.609 - 619, 1996/08
Times Cited Count：11 Percentile：66.87(Nuclear Science & Technology)no abstracts in English
collapse in high tokamak disruptionsNakamura, Yukiharu; Yoshino, Ryuji; N.Pomphrey*; S.C.Jardin*
JAERI-Research 96-023, 15 Pages, 1996/05
JAERI-Research-96-023.pdf:0.79MB
no abstracts in English
laser interferometer for large tokamakNagashima, Akira; Kawano, Yasunori; Hatae, Takaki;
Diagnostics for Experimental Thermonuclear Fusion Reactors, 0, p.235 - 243, 1996/00
no abstracts in English
Nishio, Satoshi
Purazuma, Kaku Yugo Gakkai-Shi, 72(10), p.1052 - 1060, 1996/00
no abstracts in English
Yoshino, Ryuji; Neyatani, Yuzuru; Isei, Nobuaki; Koide, Yoshihiko; Kawano, Yasunori; A.Tanga*; Campbell, D. J.*; M.F.Johnson*; L.Rossi*
IAEA-CN-60/A5-8, 0, p.685 - 695, 1995/00
no abstracts in English
