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Yoshino, Ryuji
Nuclear Fusion, 45(11), p.1232 - 1246, 2005/11
Times Cited Count：42 Percentile：76.02(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.
Tamai, Hiroshi; Ishida, Shinichi; Kurita, Genichi; Shirai, Hiroshi; Tsuchiya, Katsuhiko; Sakurai, Shinji; Matsukawa, Makoto; Sakasai, Akira
Fusion Science and Technology, 45(4), p.521 - 528, 2004/06
Times Cited Count：0 Percentile：0.00(Nuclear Science & Technology)The 1.5D time-dependent transport analysis has been carried out to investigate steady state operation scenarios with a central current hole by off-axis current drive schemes consistent with a high bootstrap current fraction for a large superconducting tokamak JT-60SC. A steady state operation scenario with HH
=1.4 and =3.7 has been obtained at I
=1.5 MA, B
=2 T and q
=5 where non-inductive currents are developed during the discharge to form a current hole with beam driven currents by tangential off-axis beams in combination with bootstrap currents by additional on-axis perpendicular beams. The bootstrap fraction increases up to nearly 75% of the plasma current and the current hole region is enlarged up to about 30% of the minor radius at 35 s from the discharge initiation. The current hole is confirmed to be sustained afterward for a long duration of 60 s. The stability analysis shows that the beta limit with the conducting wall can be about =4.5, which is substantially above the no wall ideal MHD limit.
Yoshino, Ryuji
Nuclear Fusion, 43(12), p.1771 - 1786, 2003/12
Times Cited Count：58 Percentile：83.37(Physics, Fluids & Plasmas)no abstracts in English
Kurita, Genichi; Tsuda, Takashi; Azumi, Masafumi; Ishida, Shinichi; Takeji, Satoru*; Sakasai, Akira; Matsukawa, Makoto; Ozeki, Takahisa; Kikuchi, Mitsuru
Nuclear Fusion, 43(9), p.949 - 954, 2003/09
Times Cited Count：32 Percentile：67.25(Physics, Fluids & Plasmas)In order to improve economic and environmental suitability of tokamak fusion reactors, both the accomplishment of high beta plasmas and the practical use of low activation materials to reduce the amount of radioactive waste are crucially important. Low radio-activation ferritic steel is considered as a most promising candidate for structural material in DEMO reactors, and there is the possibility of reduction of critical beta value by the deterioration of MHD stability due to ferromagnetism of ferritic steel. This paper investigates the effect of ferromagnetism with plasma flow on the beta limit of tokamak plasma by carrying out MHD stability analyses including ferromagnetic and plasma flow effects.
Ito, Hirokuni*; Hatakeyama, Mutsuo*; Tachibana, Mitsuo; Yanagihara, Satoshi
JAERI-Tech 2003-012, 34 Pages, 2003/03
JAERI-Tech-2003-012.pdf:2.87MB
The MISE was developed to evaluate low-level radiological contaminations of inner surfaces of piping. The MISE consists of a cylindrically-formed double layered type detector and a piping crawling robot, which were designed and manufactured separately. In measurements of the contaminations, an outer cylindrical detector close to the surface of piping measures -rays and 
-rays and an inner cylindrical detector set after a shielding plate for shield of -rays measures -rays. The -ray counting rates are derived by subtracting -ray counts measured by the inner detector from - and -ray counts measured by the outer detector. The robot transports the double layered type detector with observing inner surfaces of piping. The detection limit for the contamination of 
Co was found to be about 0.17Bq/cm
with measurement time of 30 seconds. It is expected that 0.2Bq/cm corresponding to clearance level of Co (0.4Bq/g) can be evaluated with measurement time of 2 seconds, which is equal to measurement speed of 54m/h.
Takeji, Satoru; Isayama, Akihiko; Ozeki, Takahisa; Tokuda, Shinji; Ishii, Yasutomo; Oikawa, Toshihiro; Ishida, Shinichi; Kamada, Yutaka; Neyatani, Yuzuru; Yoshino, Ryuji; et al.
Fusion Science and Technology (JT-60 Special Issue), 42(2-3), p.278 - 297, 2002/09
Times Cited Count：7 Percentile：3.03(Nuclear Science & Technology)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
ITER Physics Expert Group on Disruptions, Plasma Control, and MHD
Nuclear Fusion, 39(12), p.2251 - 2389, 1999/00
no abstracts in English
Tokuda, Shinji; Ozeki, Takahisa
JAERI-Research 94-030, 13 Pages, 1994/11
JAERI-Research-94-030.pdf:0.62MB
no abstracts in English
Yoshino, Ryuji; Neyatani, Yuzuru; Isei, Nobuaki; Matsukawa, Makoto; Hosogane, Nobuyuki
Purazuma, Kaku Yugo Gakkai-Shi, 70(10), p.1081 - 1101, 1994/10
no abstracts in English
Tokuda, Shinji; Ozeki, Takahisa
JAERI-Research 94-013, 16 Pages, 1994/09
JAERI-Research-94-013.pdf:0.66MB
no abstracts in English
Ishida, Shinichi; Koide, Yoshihiko; Ozeki, Takahisa; Kikuchi, Mitsuru; Tsuji, Shunji; Shirai, Hiroshi; Naito, Osamu; Azumi, Masafumi
Physical Review Letters, 68(10), p.1531 - 1534, 1992/03
Times Cited Count：54 Percentile：87.08(Physics, Multidisciplinary)no abstracts in English
Tsunematsu, Toshihide; J.Hogan*; K.Borrass*; F.Engelmann*;
JAERI-M 89-056, 47 Pages, 1989/05
no abstracts in English
Tokuda, Shinji; Yamagiwa, Mitsuru; Tsunematsu, Toshihide; Takeda, Tatsuoki
Int. Conf. on Plasma Physics, p.925 - 928, 1989/00
no abstracts in English
Nemoto, Toshiyuki; Tsunematsu, Toshihide
JAERI-M 87-062, 36 Pages, 1987/04
no abstracts in English
Tsunematsu, Toshihide; ; Nemoto, Toshiyuki; ; Takeda, Tatsuoki
JAERI-M 86-172, 54 Pages, 1986/10
no abstracts in English
; ; Sengoku, Seio; ; ; ; ; ; ; ; et al.
JAERI-M 86-148, 18 Pages, 1986/09
no abstracts in English
; ;
JAERI-M 86-089, 46 Pages, 1986/06
no abstracts in English
Takeda, Tatsuoki; ; ; ; ; ; ; ; ;
JAERI-M 85-080, 70 Pages, 1985/07
no abstracts in English
Tsunematsu, Toshihide; Takeda, Tatsuoki; ; ; ; R.Gruber*; F.Troyon*
JAERI-M 9890, 16 Pages, 1982/01
no abstracts in English
; ; ;
JAERI-M 9793, 40 Pages, 1981/11
no abstracts in English
