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Idomura, Yasuhiro; Tokuda, Shinji; Kishimoto, Yasuaki
Nuclear Fusion, 45(12), p.1571 - 1581, 2005/12
Times Cited Count：39 Percentile：75.43(Physics, Fluids & Plasmas)Using a global gyrokinetic toroidal particle code, the toroidal electron temperature gradient driven (ETG) turbulence is studied in positive and reversed shear tokamaks. In the nolinear turbulent state, the ETG turbulence in the positive and reversed shear configurations show quite different structure formations. In the positive shear configuration, the ETG turbulence is dominated by streamers which have a ballooning type structure, and the electron temperature 
profile is quickly relaxed to the marginally stable state in a turbulent time scale. In the reversed shear configuration, quasi-steady zonal flows are produced in the regative shear region, while the positive shear region is characterized by streamers. Accordingly, the electron thermal diffusivity 
has a gap structure across the 
surface, and the gradinet is sustained above the marginal value for a long time in the quasi-steady phase. The results suggest a stiffness of the profile in positive shear tokamaks, and a possibility of the Te transport barrier in reversed shear tokamaks.
Hayashi, Nobuhiko; Takizuka, Tomonori; Ozeki, Takahisa
Nuclear Fusion, 45(8), p.933 - 941, 2005/08
Times Cited Count：13 Percentile：41.28(Physics, Fluids & Plasmas)We have investigated profile formation and sustainment of current hole (CH) plasma by 1.5D transport simulations with current limit model inside CH based on Axisymmetric Tri-Magnetic-Islands equilibrium. Sharp reduction of anomalous transport in RS region can reproduce JT-60U experiments. The transport becomes neoclassical-level in RS region, which results in autonomous profile formation of ITB and CH through large bootstrap current. ITB width determined by neoclassical-level transport agrees with that in JT-60U. Energy confinement inside ITB agrees with JT-60U scaling. The scaling means that core plasma inside ITB is governed by MHD equilibrium limit, i.e., autonomous limitation of energy confinement. The plasma with large CH is sustained with full current drive by bootstrap current. The plasma with small CH and small bootstrap current fraction shrinks due to penetration of inductive current. This shrink is prevented and CH size can be controlled by appropriate external CD. CH plasma is found to respond autonomically to external CD. Application of CH plasma to reactor is discussed.
Hayashi, Nobuhiko; Takizuka, Tomonori; Ozeki, Takahisa
Proceedings of 20th IAEA Fusion Energy Conference (FEC 2004) (CD-ROM), 8 Pages, 2004/11
Profile formation and sustainment of tokamak plasmas with current hole (CH) have been investigated by using 1.5D transport simulations. A current limit model inside CH based on the Axisymmetric Tri-Magnetic-Islands equilibrium is introduced. We found that the sharp reduction of anomalous transport in the reversed-shear (RS) region can reproduce JT-60U experiment. The transport becomes neoclassical-level in RS region, which results in the autonomous formation of internal transport barrier (ITB) and CH through large bootstrap current. ITB width determined by neoclassical-level transport agrees with that in JT-60U. Energy confinement inside ITB agrees with JT-60U scaling, which means autonomous limitation of energy confinement. The plasma with large CH is sustained with the full current drive by bootstrap current. The plasma with small CH and small bootstrap current fraction shrinks due to inductive current penetration. This shrink is prevented and the CH size can be controlled by appropriate external current drive (CD). The CH plasma is found to respond autonomically to external CD.
n eigenmodesKonovalov, S. V.; Mikhailovskii, A. B.*; Shirokov, M. S.*; Kovalishen, E. A.*; Ozeki, Takahisa
Physics of Plasmas, 11(9), p.4531 - 4534, 2004/09
Times Cited Count：19 Percentile：53.04(Physics, Fluids & Plasmas)no abstracts in English
Konovalov, S. V.; Mikhailovskii, A.*; Kovalishen, E.*; Ozeki, Takahisa; Takizuka, Tomonori; Shirokov, M. S.*
Proceedings of 20th IAEA Fusion Energy Conference (FEC 2004) (CD-ROM), 8 Pages, 2004/00
Alfven eigenmodes in tokamaks with reversed magnetic shear are studied theoretically by incorporating into the mode description the effects known theories of Global, Kinetic and Toroidal Alfven Eigenmodes. In particular mode forming effect due to thermal plasma density gradient is examined. Criteria of the fast ion density and its gradient on the existence of a localized solution of the eigenmode equation is softened by this effect. Effects of finite Larmor radius, continuum damping and fast ion density gradient are also studied.
Takizuka, Tomonori
Purazuma, Kaku Yugo Gakkai-Shi, 79(11), p.1123 - 1129, 2003/11
no abstracts in English
Miura, Yukitoshi; JT-60 Team
Physics of Plasmas, 10(5), p.1809 - 1815, 2003/05
Times Cited Count：10 Percentile：31.52(Physics, Fluids & Plasmas)no abstracts in English
Kubo, Hirotaka; Sakurai, Shinji; Higashijima, Satoru; Takenaga, Hidenobu; Itami, Kiyoshi; Konoshima, Shigeru; Nakano, Tomohide; Koide, Yoshihiko; Asakura, Nobuyuki; Shimizu, Katsuhiro; et al.
Journal of Nuclear Materials, 313-316(1-3), p.1197 - 1201, 2003/03
Times Cited Count：20 Percentile：77.04(Materials Science, Multidisciplinary)no abstracts in English
Takizuka, Tomonori
Purazuma, Kaku Yugo Gakkai-Shi, 78(12), p.1282 - 1284, 2002/12
An idea of a new equilibrium of a strongly-reversed-shear tokamak plasma with a current hole is proposed. This equilibrium configuration called "Axisymmetric Tri-Magnetic-Islands (ATMI) equilibrium" has three islands, a central-negative-current island and side-positive-current islands, along the R direction and two x-points along the Z direction. The equilibrium is stable with the elongation coils when the current in the ATMI region is limited small.
; 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; JT-60 Team
Plasma Physics and Controlled Fusion, 38(12A), p.181 - 191, 1996/00
Times Cited Count：14 Percentile：46.04(Physics, Fluids & Plasmas)no abstracts in English
