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Journal Articles

Off-axis current drive and real-time control of current profile in JT-60U

Suzuki, Takahiro; Ide, Shunsuke; Oikawa, Toshihiro; Fujita, Takaaki; Ishikawa, Masao; Seki, Masami; Matsunaga, Go; Hatae, Takaki; Naito, Osamu; Hamamatsu, Kiyotaka; et al.

Nuclear Fusion, 48(4), p.045002_1 - 045002_9, 2008/04

 Times Cited Count:35 Percentile:81.18(Physics, Fluids & Plasmas)

Aiming at optimization of current profile in high-b plasmas for higher confinement and stability, a real-time control system of the minimum of the safety factor ($$q$$$$_{rm min}$$) using the off-axis current drive has been developed. The off-axis current drive can raise safety factor in the center and help to avoid instability that limits performance of the plasma. The system controls injection power of lower-hybrid (LH) waves, and hence, its off-axis driven current in order to control $$q$$$$_{min}$$. The real-time control of $$q$$$$_{rm min}$$ is demonstrated in a high-$$beta$$ plasma, where $$q$$$$_{rm min}$$ follows the temporally changing reference $$q$$$$_{min,ref}$$ from 1.3 to 1.7. Applying the control to another high-$$beta$$ discharge ($$beta$$$$_{rm N}$$=1.7, $$beta$$$$_{rm p}$$=1.5) with $$m/n$$=2/1 neo-classical tearing mode (NTM), $$q$$$$_{rm min}$$ was raised above 2 and the NTM was suppressed. The stored energy increased by 16% with the NTM suppressed, since the resonant rational surface was eliminated. For the future use for current profile control, current density profile for off-axis neutral beam current drive (NBCD) is for the first time measured, using motional Stark effect (MSE) diagnostic. Spatially localized NBCD profile was clearly observed at the normalized $rm minor radius $rho$$ of about 0.6-0.8. The location was also confirmed by multi-chordal neutron emission profile measurement. The total amount of the measured beam driven current was consistent with the theoretical calculation using the ACCOME code. The CD location in the calculation was inward-shifted than the measurement.

Journal Articles

Off-axis current drive and current profile control in JT-60U

Suzuki, Takahiro; Ide, Shunsuke; Oikawa, Toshihiro; Fujita, Takaaki; Ishikawa, Masao*; Seki, Masami; Matsunaga, Go; Takechi, Manabu; Naito, Osamu; Hamamatsu, Kiyotaka; et al.

Proceedings of 21st IAEA Fusion Energy Conference (FEC 2006) (CD-ROM), 8 Pages, 2007/03

For the first time, we have measured the current density profile for off-axis neutral beam current drive (NBCD), using motional Stark effect (MSE) diagnostic. A spatially localized NBCD profile was clearly observed at $$rho=0.6-0.8$$. The location was also confirmed by neutron emission profile measurement. The total amount of the driven current (0.15MA) was consistent with the decrease in the surface loop voltage. The off-axis current drive can raise safety factor (q) in the center and help to avoid instability that limits performance of the plasma. We have developed a real-time control system of the minimum q (qmin), using the off-axis current drive. Injection power of lower hybrid (LH) waves, and hence, its off-axis driven current controls qmin. In a high $$beta$$ plasma ($$beta_{N}=1.7$$, $$beta_{p}=1.5$$), the system was adopted to control qmin. With the control, qmin was raised and MHD fluctuations were suppressed. The stored energy increased by 16% with the MHD fluctuations suppressed.

Oral presentation

Design study of the plasma control system for JT-60SA

Kurihara, Kenichi; Kawamata, Yoichi; Sueoka, Michiharu; Nakazato, Mikoto; Sakata, Shinya; Kiyono, Kimihiro; Naito, Osamu; Ozeki, Takahisa; Takenaga, Hidenobu; Suzuki, Takahiro; et al.

no journal, , 

no abstracts in English

Oral presentation

Effect of a nonlinear scalar equilibrium constraint for current profile reconstruction

Kurihara, Kenichi; Kawamata, Yoichi; Sueoka, Michiharu; Nakazato, Mikoto; Suzuki, Takahiro; Fujita, Takaaki; Takenaga, Hidenobu; Ide, Shunsuke; Kamada, Yutaka

no journal, , 

no abstracts in English

Oral presentation

Off-axis current drive and current profile control in JT-60U

Suzuki, Takahiro; Ide, Shunsuke; Oikawa, Toshihiro; Fujita, Takaaki; Ishikawa, Masao; Seki, Masami; Matsunaga, Go; Takechi, Manabu; Naito, Osamu; Hamamatsu, Kiyotaka; et al.

no journal, , 

no abstracts in English

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