Initial results of electron cyclotron range of frequency (ECRF) operation and experiments in JT-60U

Ikeda, Yoshitaka; Kasugai, Atsushi; Takahashi, Koji; Kajiwara, K.; Isayama, A.; Ide, S.; Terakado, M.; Shinozaki, S.; Yokokura, K.; Anno, K.; Shimono, M.; Hiranai, S.; Haga, Kazuo; Kajiyama, Atsushi; Ikeda, Y.; Moriyama, S.; Tsuneoka, M.; Sakamoto, K.; Hamamatsu, K.; Oikawa, T.; Kamada, Y.; Naito, O.; Seki, M.; Ushigusa, K.; Imai, T.; Yamamoto, T.; Fujii, T.

doi:10.1016/s0920-3796(00)00511-1

Cited by 41 publications

(23 citation statements)

References 10 publications

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“…In JT-60U experiments, power modulation at several tens of Hz had been done to investigate heat wave propagation since the initial phase of first gyrotron operation [19].…”

Section: Stabilization Of 2/1 Ntm By Modulated Eccdmentioning

confidence: 99%

Neoclassical tearing mode control using electron cyclotron current drive and magnetic island evolution in JT-60U

et al. 2009

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The results of stabilizing neoclassical tearing modes (NTMs) with electron cyclotron current drive (ECCD) in JT-60U are described with the emphasis on the effectiveness of the stabilization. The range of the minimum EC wave power needed for complete stabilization of an m/n = 2/1 NTM was experimentally identified for two regimes using unmodulated ECCD to clarify the NTM behaviors with different plasma parameters: 0.2 < j EC /j BS < 0.4 for W sat /d EC ∼ 3 and W sat /W marg ∼ 2, and 0.35 < j EC /j BS < 0.46 for W sat /d EC ∼ 1.5 and W sat /W marg ∼ 2. Here, m and n are the poloidal and toroidal mode numbers; j EC and j BS the EC-driven current density and bootstrap current density at the mode rational surface; W sat , W marg and d EC the full island width at saturation, marginal island width and full width at the half maximum of the ECCD deposition profile, respectively. Stabilization of a 2/1 NTM using modulated ECCD synchronized with a mode rotation of about 5 kHz was performed, in which it was found that the stabilization effect degrades when the phase of the modulation deviates from that of the ECCD at the island O-point. The decay time of magnetic perturbation amplitude due to the ECCD increases by 50% with a phase shift of ±50 • from the O-point ECCD, thus revealing the importance of the phasing of modulated ECCD. For near X-point ECCD, the NTM amplitude increases, revealing a destabilization effect. It was also found that modulated ECCD at the island O-point has a stronger stabilization effect than unmodulated ECCD by a factor of more than 2.

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“…In JT-60U experiments, power modulation at several tens of Hz had been done to investigate heat wave propagation since the initial phase of first gyrotron operation [19].…”

Section: Stabilization Of 2/1 Ntm By Modulated Eccdmentioning

confidence: 99%

Neoclassical tearing mode control using electron cyclotron current drive and magnetic island evolution in JT-60U

et al. 2009

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“…After installation of the 110 GHz EC wave injection system [23,24] in JT-60U, experiments on tearing mode stabilization by local current drive and heating at the magnetic island using the first harmonic EC wave were performed [5,25]. The shape of the plasma cross-section is shown in Fig.…”

Section: Stabilization Of the 3/2 Ntm By Eccd/ech At The Magnetic Islandmentioning

confidence: 99%

Long sustainment of quasi-steady-state high _pH mode discharges in JT-60U

et al. 2001

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Quasi-steady-state high βp H mode discharges performed by suppressing neoclassical tearing modes (NTMs) are described. Two operational scenarios have been developed for long sustainment of the high βp H mode discharge: NTM suppression by profile optimization, and NTM stabilization by local electron cyclotron current drive (ECCD)/electron cyclotron heating (ECH) at the magnetic island. Through optimization of pressure and safety factor profiles, a high βp H mode plasma with H89PL = 2.8, HHy,2 = 1.4, βp ≈ 2.0 and βN ≈ 2.5 has been sustained for 1.3 s at small values of collisionality νe * and ion Larmor radius ρi * without destabilizing the NTMs. Characteristics of the NTMs destabilized in the region with central safety factor above unity are investigated. The relation between the beta value at the mode onset β on N and that at the mode disappearance β off N can be described as β off N /β on N = 0.05-0.4, which shows the existence of hysteresis. The value of βN /ρi * at the onset of an m/n = 3/2 NTM has a collisionality dependence, which is empirically given by βN /ρi * ∝ ν 0.36 e * . However, the profile effects such as the relative shapes of pressure and safety factor profiles are equally important. The onset condition seems to be affected by the strength of the pressure gradient at the mode rational surface. Stabilization of the NTM by local ECCD/ECH at the magnetic island has been attempted. A 3/2 NTM has been completely stabilized by EC wave injection of 1.6 MW.

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“…22 The main purpose of the system is localized heating and current drive ͑ECH and ECCD͒ for suppression of the neoclassical tearing mode, verification of ECCD application in a fusion plasma, pure electron heating, transport studies such as heat pulse propagation, and so forth. The power source is a gyrotron which was designed based on a 170 GHz gyrotron developed by JAERI for ITER R & D. 23 For a use on JT-60U, the oscillation frequency of 110 GHz was chosen.…”

Section: Jt-60u Ecrf Systemmentioning

confidence: 99%

“…Some impacts such as extension of the sawtooth periods have been observed. 22,25,26 Typical changes of the T e profile ͑against the major radius R) in a RS and a high ␤ p H-mode plasma with on axis fundamental O-mode ECH are shown in Fig. 1.…”

Section: Jt-60u Ecrf Systemmentioning

confidence: 99%

Latest progress in steady state plasma research on the Japan Atomic Energy Research Institute Tokamak-60 Upgrade

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2000

Physics of Plasmas

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The JT-60U ͓Y. Kusama and the JT-60 team, Phys. Plasmas 6, 1935 ͑1999͔͒ high performance plasmas, such as high poloidal-beta high-confinement mode ͑high ␤ p H-mode͒ and reversed magnetic shear ͑RS͒ plasmas, have been optimized towards a regime of steady state operation concerning high confinement, high ␤ and high bootstrap current fraction which are requirements of a steady state fusion plasma. What is essential to keep improved confinement in these plasmas is to maintain the internal and/or the edge transport barriers ͑ITB and/or ETB͒. A key issue to achieve non-inductive current drive relevant to a steady state fusion reactor is to increase the fraction of the bootstrap current and match the spatial profile to the optimum. In JT-60U, RS plasmas have been optimized not only for the high performance but also for reactor relevant steady state research. In 1999, as the result of the optimization, the equivalent deuterium-tritium ͑D-T͒ fusion gain (Q DT eq ) of 0.5 was sustained for 0.8 s, which is roughly equal to the energy confinement time, by utilizing feedback control of the stored energy. Furthermore, in a RS plasma with H-mode edge, a confinement enhancement factor of 3.6 was maintained for 2.7 s with a large bootstrap current fraction. In addition to the existing radio frequency and the negative-ion based neutral beam heating systems, the newly installed electron cyclotron range of frequency system extended the improved confinement study to a regime where the electron temperature is higher than the ion temperature. The required power to obtain the internal transport barrier in a RS plasma was found not to be sensitive to the toroidal magnetic field. The regime of improved confinement was extended to higher electron density using argon puffing.

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Initial results of electron cyclotron range of frequency (ECRF) operation and experiments in JT-60U

Cited by 41 publications

References 10 publications

Neoclassical tearing mode control using electron cyclotron current drive and magnetic island evolution in JT-60U

Neoclassical tearing mode control using electron cyclotron current drive and magnetic island evolution in JT-60U

Long sustainment of quasi-steady-state high _pH mode discharges in JT-60U

Latest progress in steady state plasma research on the Japan Atomic Energy Research Institute Tokamak-60 Upgrade

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Initial results of electron cyclotron range of frequency (ECRF) operation and experiments in JT-60U

Cited by 41 publications

References 10 publications

Neoclassical tearing mode control using electron cyclotron current drive and magnetic island evolution in JT-60U

Neoclassical tearing mode control using electron cyclotron current drive and magnetic island evolution in JT-60U

Long sustainment of quasi-steady-state high pH mode discharges in JT-60U

Latest progress in steady state plasma research on the Japan Atomic Energy Research Institute Tokamak-60 Upgrade

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Long sustainment of quasi-steady-state high _pH mode discharges in JT-60U