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Sakamoto, Yoshiteru; Ide, Shunsuke; Yoshida, Maiko; Koide, Yoshihiko; Fujita, Takaaki; Takenaga, Hidenobu; Kamada, Yutaka
Plasma Physics and Controlled Fusion, 48(5A), p.A63 - A70, 2006/05
Times Cited Count：34 Percentile：73.6(Physics, Fluids & Plasmas)no abstracts in English
Takenaga, Hidenobu; Oyama, Naoyuki; Bruskin, L. G.*; Mase, Atsushi*; Takizuka, Tomonori; Fujita, Takaaki
Plasma Physics and Controlled Fusion, 48(5A), p.A401 - A408, 2006/05
Times Cited Count：6 Percentile：21.5(Physics, Fluids & Plasmas)no abstracts in English
Takechi, Manabu; Fujita, Takaaki; Ishii, Yasutomo; Ozeki, Takahisa; Suzuki, Takahiro; Isayama, Akihiko; JT-60 Team
Nuclear Fusion, 45(12), p.1694 - 1699, 2005/12
Times Cited Count：7 Percentile：24.62(Physics, Fluids & Plasmas)High performance reversed shear discharges with strong internal transport barrier (ITB) and flat pressure profile in the plasma core region disrupt frequently even with low beta. We analyzed MHD instabilities leading to low beta disruption with measuring fluctuations and current profile with MSE measurement. We mainly observed two type of disruptions. One is the disruption without precursor at 
. The other is the disruption with n=1 precursor of 
100 ms. To explain these characteristics of disruption, we introduce the simple model such as, disruption occurs when the both MHD instabilities at plasma surface and at safety factor being equal to surface mode are unstable. This simple model can explain almost all observed disruption by two process. One is the surface mode triggered disruption, which occurs when qeff change, corresponding q surface at ITB layer changes discretely. The other is the internal mode triggered disruption, which occurs when corresponding q surface become unstable gradually.
n eigenmodes in reversed shear plasmas in JT-60U negative-ion-based neutral beam injection dischargesTakechi, Manabu; Fukuyama, Atsushi*; Ishikawa, Masao; Cheng, C. Z.*; Shinohara, Koji; Ozeki, Takahisa; Kusama, Yoshinori; Takeji, Satoru*; Fujita, Takaaki; Oikawa, Toshihiro; et al.
Physics of Plasmas, 12(8), p.082509_1 - 082509_7, 2005/08
Times Cited Count：34 Percentile：71.2(Physics, Fluids & Plasmas)Rapid frequency sweeping modes observed in reversed magnetic shear (RS) plasmas on the Japan Atomic Energy Research Institute Tokamak 60 Upgrade (JT-60U) have been identified as Reversed-Shear-induced Alfvn Eigenmodes (RSAEs), which are ideal MHD Alfvn eigenmodes (AEs) localized to the region of minimum safety factor, 
, and are excited by negative-ion-based neutral beam injection. The chirping and subsequent saturation of the mode frequency are consistent with theoretical predictions for the transition from RSAEs to Toroidal Alfv
n eigenmodes (TAEs). The previously observed rapid frequency sweeping modes in ion cyclotron wave heated plasmas in JT-60U can also be similarly explained. The observed AE amplitude is largest during the transition from RSAEs to TAEs, and fast ion loss is observed when the AE amplitude is largest at this transition. It is preferable to operate outside the transition range of 
, e.g., 2.4 
2.7 for the n = 1 AE to avoid substantial fast ion loss in RS plasmas.
Sakamoto, Yoshiteru; Fujita, Takaaki; Ide, Shunsuke; Isayama, Akihiko; Takechi, Manabu; Suzuki, Takahiro; Takenaga, Hidenobu; Oyama, Naoyuki; Kamada, Yutaka; JT-60 Team
Nuclear Fusion, 45(7), p.574 - 580, 2005/07
Times Cited Count：41 Percentile：76.9(Physics, Fluids & Plasmas)This paper reports results on the progress in stationary discharges with a large bootstrap current fraction in JT-60U towards steady-state tokamak operation. In weak shear plasma regime, high-_p ELMy H-mode discharges have been optimized under nearly full non-inductive current drive by the large bootstrap current fraction (fBS
50%) and the beam driven current fraction (fBD40%), which was sustained for 2.3s with stationary condition. The high confinement enhancement factor H892.3 (HH98y21.0) was also sustained under the condition of TeTi. In reversed shear plasma regime, the large bootstrap current fraction (fBS75%) has been sustained for 7.4 s under nearly full non-inductive current drive condition. The high confinement enhancement factor H893.0 (HH98y21.7) was also sustained, and the profiles of current and pressure approached the stationary condition. The large bootstrap current and the off-axis beam driven current sustained this reversed q-profile. This duration was limited only by the duration of the neutral beam injection.
plasmas through stability control in Japan Atomic Energy Research Institute tokamak-60 upgradeIsayama, Akihiko; JT-60 Team
Physics of Plasmas, 12(5), p.056117_1 - 056117_10, 2005/05
Times Cited Count：28 Percentile：65.7(Physics, Fluids & Plasmas)no abstracts in English
Takei, Nahoko; Nakamura, Yukiharu; Tsutsui, Hiroaki*; Yoshino, Ryuji; Kawano, Yasunori; Ozeki, Takahisa; Tobita, Kenji; Iio, Shunji*; Shimada, Ryuichi*; Jardin, S. C.*
Plasma Physics and Controlled Fusion, 46(12), p.1815 - 1830, 2004/12
Times Cited Count：3 Percentile：9.99(Physics, Fluids & Plasmas)no abstracts in English
Sakamoto, Yoshiteru; Suzuki, Takahiro; Ide, Shunsuke; Koide, Yoshihiko; Takenaga, Hidenobu; Kamada, Yutaka; Fujita, Takaaki; Fukuda, Takeshi; Takizuka, Tomonori; Shirai, Hiroshi; et al.
Nuclear Fusion, 44(8), p.876 - 882, 2004/08
Times Cited Count：33 Percentile：71.1(Physics, Fluids & Plasmas)Response of the ion thermal diffusivity to the radial electric field Er shear has been investigated in JT-60U and the following results were found. (1) In the case of positive magnetic shear (PS) plasma, the ion thermal diffusivity in the core region shows L mode state, weak internal transport barrier (ITB), and strong ITB depending upon the heating power. In the case of reversed magnetic shear (RS) plasma, however, no power degradation of the ion thermal diffusivity is observed. (2) In the case of weak ITB, the ion thermal diffusivity decreases gradually with increasing the Er shear for both PS and RS plasmas. There exists a threshold of an effective Er shear to change its state from weak to strong ITBs. (3) The threshold of the effective Er shear in the case of RS plasma is small compared with that in the case of PS plasma.
Oikawa, Toshihiro; Tsuchiya, Katsuhiko; Kurihara, Kenichi; Kawamata, Yoichi; Fukuda, Takeshi*; Fujita, Takaaki; Neyatani, Yuzuru
Fusion Engineering and Design, 70(2), p.175 - 183, 2004/02
Times Cited Count：6 Percentile：40.72(Nuclear Science & Technology)The real-time feedback control of the plasma stored energy has been developed for control of the plasma MHD stability in the JT-60U tokamak. The plasma stored energy can be detected with high accuracy in real-time by the function parametrization method for various plasmas available in JT-60U, such as the ohmic plasma, the L-mode, the H-mode, the high poloidal beta mode and the reversed shear mode over a wide range of the plasma parameters. By manipulating the neutral beam injection power, the plasma stored energy has been successfully controlled along the preprogrammed reference waveform. Especially in the reversed shear mode, this feedback control scheme has improved the reproducibility of the formation of the internal transport barrier, and the MHD instability could be suppressed with keeping the normalized beta in the stable region. The D-T equivalent fusion amplification gain of 0.5 was sustained for 0.8 s in a reversed shear plasma by employing this feedback control scheme.
Ide, Shunsuke; Suzuki, Takahiro; Sakamoto, Yoshiteru; Takenaga, Hidenobu; Fujita, Takaaki; Oyama, Naoyuki; Isayama, Akihiko; Koide, Yoshihiko; Kamada, Yutaka; JT-60 Team
Nuclear Fusion, 44(1), p.87 - 92, 2004/01
Times Cited Count：19 Percentile：53.39(Physics, Fluids & Plasmas)no abstracts in English
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
Oikawa, Toshihiro; Tsuchiya, Katsuhiko; Kurihara, Kenichi; Kawamata, Yoichi; Fukuda, Takeshi*; Fujita, Takaaki; Akasaka, Hiromi; Yonekawa, Izuru; Neyatani, Yuzuru
JAERI-Research 2003-027, 19 Pages, 2003/12
JAERI-Research-2003-027.pdf:1.14MB
no abstracts in English
Takenaga, Hidenobu; Higashijima, Satoru; Oyama, Naoyuki; Bruskin, L. G.; Koide, Yoshihiko; Ide, Shunsuke; Shirai, Hiroshi; Sakamoto, Yoshiteru; Suzuki, Takahiro; Hill, K. W.*; et al.
Nuclear Fusion, 43(10), p.1235 - 1245, 2003/10
Times Cited Count：71 Percentile：88.64(Physics, Fluids & Plasmas)no abstracts in English
Tani, Keiji; Tobita, Kenji; Nishio, Satoshi; Iio, Shunji*; Tsutsui, Hiroaki*; Aoki, Takayuki*
Denki Gakkai Purazuma Kenkyukai Shiryo (PST-03-39), p.13 - 18, 2003/09
Studies were made on ripple losses of fusion produced alpha particles in a tokamak reactor with a non-circular plasma cross-section by using an orbit-following Monte-Carlo code. A preliminary estimation of ripple loss of alpha particles in VECTOR, a compact tokamak type fusion reactor, with a negative magnetic shear was also made
Sengoku, Seio
Denki Gakkai Purazuma Kenkyukai Shiryo (PST-03-41), p.23 - 26, 2003/09
no abstracts in English
Ishii, Yasutomo; Azumi, Masafumi; Kishimoto, Yasuaki; Leboeuf, J. N.*
Nuclear Fusion, 43(7), p.539 - 546, 2003/07
no abstracts in English
Ishii, Yasutomo; Azumi, Masafumi; Kishimoto, Yasuaki; Leboeuf, J. N.*
Nuclear Fusion, 43(7), p.539 - 546, 2003/07
Times Cited Count：26 Percentile：61.38(Physics, Fluids & Plasmas)no abstracts in English
Tobita, Kenji; Nakayama, Takeshi*; Konovalov, S. V.; Sato, Masayasu
Plasma Physics and Controlled Fusion, 45(2), p.133 - 143, 2003/02
Times Cited Count：35 Percentile：70.78(Physics, Fluids & Plasmas)no abstracts in English
Nakamura, Yukiharu; Tsutsui, Hiroaki*; Takei, Nahoko*; Sakamoto, Yoshiteru; Fujita, Takaaki; Sugihara, Masayoshi; Ozeki, Takahisa; Tobita, Kenji; Konishi, Satoshi; Iio, Shunji*; et al.
Europhysics Conference Abstracts, 27A, 4 Pages, 2003/00
no abstracts in English
Takenaga, Hidenobu; JT-60 Team
Proceedings of 30th EPS Conference on Controlled Fusion and Plasma Physics (CD-ROM), 4 Pages, 2003/00
no abstracts in English
