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ABSTRACT: The plasma rotation necessary for stabilization of resistive-wall modes (RWMs) is investigated by controlling the toroidal plasma rotation with external momentum input by injection of tangential neutral beams. The observed threshold is 0.3% of the Alfvén velocity and much smaller than the previous experimental results obtained with magnetic braking. This low critical rotation has a very weak beta dependence as the ideal wall limit is approached. These results indicate that for large plasmas such as in future fusion reactors with low rotation, the requirement of the additional feedback control system for stabilizing RWM is much reduced.
Physical Review Letters 03/2007; 98(5):055002. · 7.37 Impact Factor
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H Tamai, G Kurita,
M Matsukawa,
K Urata,
S Sakurai,
K Tsuchiya,
A Morioka,
Y M Miura,
K Kizu,
Y Kamada,
A Sakasai,
S Ishida
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ABSTRACT: Plasma control on high-βN steady-state operation for JT-60 superconducting modification is discussed. Accessibility to high-βN exceeding the free-boundary limit is investigated with the stabilising wall of reduced-activated ferritic steel and the active feedback control of the in-vessel non-axisymmetric field coils. Taking the merit of superconducting magnet, advanced plasma control for steady-state high performance operation could be expected.
Plasma Science and Technology 10/2006; 6(3):2281. · 0.41 Impact Factor
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ABSTRACT: This paper describes the latest design of poloidal field coil configuration in the national centralized tokamak (NCT), that is a new design based on the former superconducting coil tokamak JT-60SC. The most notable design change was made for the outer equilibrium field (EF) coils to increase a plasma shaping parameter S(=q<sub>95</sub>*I<sub>p </sub>/a*B<sub>t</sub>) and to make off-axis heating using N-NBI possible. As a result, the maximum plasma shaping parameter of ~ 7 was obtained by double null divertor configuration with a lower aspect ratio of A ~ 2.6. It was confirmed that two additional EF coils are useful for the plasma squareness control, but only one is finally adopted for ITER plasma simulation and to keep compatibility of off-axis N-NBI heating
IEEE Transactions on Appiled Superconductivity 07/2006; · 1.04 Impact Factor
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ABSTRACT: Evolution of the current density profile associated with magnetic island formation of an m/n=2/1 tearing mode was measured using a motional Stark effect (MSE) diagnostic for the first time in the JT-60U tokamak. With the island growth, the current density profile turned flat at the radial region of the island, followed by an appearance of a hollow structure. As the island shrank, the flat region became narrower, and it finally diminished after the disappearance of the island. The fluctuation of the local poloidal magnetic field from MSE showed a strong correlation with a slow island rotation. This indicates that the observed deformation in the current density profile is localized at the island O point.
Physical Review Letters 05/2005; 94(12):125003. · 7.37 Impact Factor
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A. Sakasai,
S. Ishida,
M. Matsukawa, G. Kurita,
N. Akino,
T. Ando,
T. Arai,
H. Ichige,
A. Kaminaga,
T. Kato, [......],
T. Sasajima,
S. Takeji,
H. Tamai,
K. Tsuchiya,
K. Urata,
J. Yagyu,
K. Tobita,
H. Takenaga,
K. Shimizu,
M. Kikuchi
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ABSTRACT: The modification of JT-60 is planned as a fully superconducting tokamak (JT-60SC). The mission of JT-60SC program is to establish scientific and technological bases for an advanced operation in an economically and environmentally attractive DEMO reactor and ITER. The research objectives are to accomplish high performance steady state operation with high beta and non-inductive full current drive, with high bootstrap current fraction, and demonstrate the plasma applicability of reduced-activation material for a plasma of break-even class relevant to the reactor plasma. Basic design of JT-60SC has been completed and the detailed design is under way. The engineering design for main components of JT-60SC is described.
Fusion Engineering, 2002. 19th Symposium on; 02/2002
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Fusion Engineering and Design 01/1998; 38(4):417 - 428. · 1.49 Impact Factor
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G. Kurita,
K. Ushigusa,
M. Kikuchi,
K. Nagashima,
Y. Neyatani,
N. Miya,
N. Toyoshima,
Y. Takahashi,
T. Hayashi,
M. Kuriyama, [......],
K. Nakagawa,
K. Mori,
T. Kitai,
S. Oguri,
M. Otsuka,
K. Nakashima,
S. Nakagawa,
T. Suzuki,
M. Nagami,
H. Kishimoto
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ABSTRACT: JT-60 Super Upgrade has been designed as an experimental device to
establish an integrated scientific basis of a steady-state tokamak
operation. A long pulse (1000 s-1 hr) full non-inductive current drive
will be investigated at the plasma current of 5-6 MA. Physics and
engineering features of the JT-60SU design are given. MHD stability
analyses concerning low n ideal and resistive modes and n infinity
ballooning modes are carried out
Fusion Engineering, 1997. 17th IEEE/NPSS Symposium; 11/1997
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M. Kikuchi,
K. Nagashima,
T. Aoyagi, G. Kurita,
K. Ushigusa,
Y. Neyatani,
T. Kubo,
K. Tobita,
K. Masaki,
A. Kaminaga, [......],
S. Nakagawa,
M. Kuriyama,
T. Yamamoto,
Y. Takahashi,
T. Hayashi,
M. Nagami,
T. Yoshida,
M. Otsuka,
K. Nakashima,
T. Suzuki
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ABSTRACT: Basic design parameters of the JT-60SU device are described. The
design addresses wide range of shape and current profile control for the
tokamak concept improvement with deuterium operation
Fusion Engineering, 1995. SOFE '95. 'Seeking a New Energy Era'., 16th IEEE/NPSS Symposium;
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ABSTRACT: The high beta plasma of βN~4.2 (>4li) exceeding no wall limit has been obtained with wall stabilizing effect and reached to ideal wall limit. The critical rotation for stabilizing resistive wall mode (RWM) was investigated by controling toroidal plasma rotation by changing the combination of tangential NBs without magnetic braking. The observed critical rotation is Vt/VA~0.2% and was much smaller than previous experimental results with magnetic braking. After ferritic steel tiles installation as first wall, the net NB power increased by ~30% for the large plasma placed enough close to the first wall to stabilize the RWM. We can raise the beta and control of toroidal plasma rotation for large volume plasma due to increase of the net NB power. Wall stabilization effects were observed by changing the clearance between plasma surface and the first wall.
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M Takechi,
G Matsunaga, G Kurita,
S Sakurai,
H Fujieda,
S Ide,
N Aiba,
T Bolzonella,
A Ferro,
L Novello,
E Gaio,
F Villone,
Team
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ABSTRACT: One of the important missions of JT-60SA is to demonstrate and develop steady-state high beta operation in order to supplement ITER toward DEMO. Specifications of plasma control system including the stabilizing plate, the RWM control coils, the error field correction coils and fast position control coils were determined based on simulations and expected plasma regime. Full non-inductive steady-state plasma with β N = 4.3 at I p =2.3 MA will be achieved with these control systems. Simulation of plasma disruption was also performed to evaluate design values of Electro Magnetic forces of components.
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K. Nagashima,
M. Kikuchi, G. Kurita,
T. Ozeki,
T. Aoyagi,
K. Ushigusa,
Y. Neyatani,
T. Kubo,
K. Mori,
S. Nakagawa,
M. Kuriyama,
M. Nagami
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ABSTRACT: The JT-60 Super Upgrade (JT-60SU) is an upgraded tokamak device of JT-60U for developing the steady-state reactor and advanced tokamak operation in the International Thermonuclear Experimental Reactor. The device is planned to utilize the JT-60 facilities fully and to minimize the needed modification. The major radius is 4.8 m and the maximum plasma current is 10 MA. Neutral beam injection with 750 keV beam energy is the primary heating method. The machine is capable of steady-state operation with high density up to 8.8 × 1019 m−3 at 5 MA plasma current. The high operating density, over the Greenwald et al. limit, is critically important in order to achieve high bootstrap current fraction. Ballooning mode and low n ideal magnetohydrodynamic (MHD) mode including the bootstrap current were analyzed for steady-state operation. The current profile must be optimized to obtain a normalized beta up to 3. The plasma configuration with high triangularity was adopted in order to get good MHD stability and high energy confinement. A compact divertor was designed in order to get the large plasma space.
Fusion Engineering and Design.
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M. Matsukawa,
S. Ishida,
A. Sakasai,
K. Urata,
I. Senda, G. Kurita,
H. Tamai,
S. Sakurai,
Y.M. Miura,
K. Masaki,
K. Shimada,
T. Terakado
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ABSTRACT: The analyses of the plasma position and shape control in the superconducting tokamak JT-60SC in JAERI are presented. The vacuum vessel and stabilizing plates located closely to the plasma are modeled in 3 dimension, and we can take into account the large ports in the vacuum vessel. The linear numerical model used in the design for the plasma feedback control system is based on Grad–Shafranov equation, which allows the plasma surface deformation. For a slower control of the plasma shape, the superconducting equilibrium field (EF) coils outside toroidal field coils are used, while for a fast control of the plasma position, in-vessel normal conducting coils (IV coil) are used. It is shown that the available loop voltages of the EF and IV coils are very limited, but there are sufficient accuracy and acceptable response time of plasma position and shape control.
Fusion Engineering and Design.
