Control of the resistive wall mode with internal coils in the DIII–D tokamak

Okabayashi, M.; Bialek, J.; Bondeson, A.; Chance, M. S.; Chu, M. S.; Garofalo, A. M.; Hatcher, R.; In, Y.; Jackson, G.L.; Jayakumar, R. J.; Jensen, T. H.; Katsuro-Hopkins, O.; Haye, R. J. La; Liu, Yueqiang; Navratil, G.A.; Reimerdes, H.; Scoville, J.T.; Strait, E.J.; Takechi, M.; Turnbull, A. D.; Gohil, P.; Kim, J. S.; Makowski, M. A.; Manickam, J.; Ménard, J.

doi:10.1088/0029-5515/45/12/028

Cited by 89 publications

(114 citation statements)

References 25 publications

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“…More detail can be found in Ref. 26 Without feedback, the OFM activity showed the downward frequency chirping, forming a nearly steady-state n ¼ 1 mode of $30 G as shown in the left column of Fig. 14.…”

Section: Response To Applied N ¼ 1 External Fieldmentioning

confidence: 89%

“…The feedback hardware used was a standard feedback hardware arrangement. 26 The two arrays of six feedback I-coils are located inside the vacuum vessel above and below the midplane. The connection of the upper/lower coils was optimized for producing the m=n ¼ 3=1 mode pattern.…”

Section: Experimental Arrangementmentioning

confidence: 99%

“…More details about the hardware are found in Ref. 26. The experimental results reported here were carried out without feedback applied except for those in Sec.…”

Section: Experimental Arrangementmentioning

confidence: 99%

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Off-axis fishbone-like instability and excitation of resistive wall modes in JT-60U and DIII-D

Okabayashi¹,

Matsunaga²,

deGrassie³

et al. 2011

Physics of Plasmas

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An energetic-particle (EP)-driven "off-axis-fishbone-like mode (OFM)" often triggers a resistive wall mode (RWM) in JT-60U and DIII-D devices, preventing long-duration high-b N discharges. In these experiments, the EPs are energetic ions (70-85 keV) injected by neutral beams to produce high-pressure plasmas. EP-driven bursting events reduce the EP density and the plasma rotation simultaneously. These changes are significant in high-b N low-rotation plasmas, where the RWM stability is predicted to be strongly influenced by the EP precession drift resonance and by the plasma rotation near the q ¼ 2 surface (kinetic effects). Analysis of these effects on stability with a self-consistent perturbation to the mode structure using the MARS-K code showed that the impact of EP losses and rotation drop is sufficient to destabilize the RWM in low-rotation plasmas, when the plasma rotation normalized by Alfvén frequency is only a few tenths of a percent near the q ¼ 2 surface. The OFM characteristics are very similar in JT-60U and DIII-D, including nonlinear mode evolution. The modes grow initially like a classical fishbone, and then the mode structure becomes strongly distorted. The dynamic response of the OFM to an applied n ¼ 1 external field indicates that the mode retains its external kink character. These comparative studies suggest that an energetic particle-driven "off-axis-fishbone-like mode" is a new EP-driven branch of the external kink mode in wall-stabilized plasmas, analogous to the relationship of the classical fishbone branch to the internal kink mode.

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Section: Response To Applied N ¼ 1 External Fieldmentioning

confidence: 89%

Section: Experimental Arrangementmentioning

confidence: 99%

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Off-axis fishbone-like instability and excitation of resistive wall modes in JT-60U and DIII-D

Okabayashi¹,

Matsunaga²,

deGrassie³

et al. 2011

Physics of Plasmas

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show abstract

“…This chamber is surrounded by magnetic coils in toroidal and poloidal configurations, which generate the magnetic field with sufficient strength to contain the plasma, the combination of the two magnetic field orientations causes an induced magnetic field in the form of a directional plasma current, maintaining the plasma flow within the magnetic field (as seen in diagram 1) and preventing collision with the outer wall [18,19,20]. The inside of the chamber is usually lined with a heat-resistive element, such as lead, lithium, and boron to help the chamber withstand the intense heat generated by the plasma [21,22,23].…”

Section: Introductionmentioning

confidence: 99%

Analysis of Tokamak fusion device parameters affecting the efficiency of Tokamak operation

El-zmeter

Schmiga²,

Boyd-Weetman³

et al. 2017

PAMR

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Nuclear Power has been available as a relatively clean and reliable energy source for several decades. While tokamak engines have been in existence almost as long as successful fission-powered nuclear generators, they have not yet reached operational success for energy generation. This meta study collates key fusion device parameters and determines ideas on the applicability of fusion devices for energy. This paper supports the argument that toroidal tokamaks are not limited by volume whereas spherical designs have a potential volume limit, spherical tokamaks use a lower magnetic field current than toroidal tokamaks. Further scientific and engineering progress is required before tokamak devices can be a viable technology to be used for energy generation.

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“…The vertical position instability [48][49][50][51][52] is controlled [50][51][52] as a matter of routine in all shaped tokamaks. Active control of the resistive wall mode (RWM) [53,54] has been demonstrated using magnetic mode detection and applied 3D fields [55][56][57][58][59][60]. Control of the m/n=2/1 neoclassical tearing mode [61,62] has been demonstrated using gyrotrons to drive currents inside the magnetic island [62][63][64][65][66][67].…”

Section: : Introductionmentioning

confidence: 99%