Stabilization of the external kink and the resistive wall mode

Chu, M. S.; Okabayashi, M.

doi:10.1088/0741-3335/52/12/123001

Cited by 200 publications

(299 citation statements)

References 176 publications

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“…[12] for mode calculations in a cylindrical case and the recent review paper of Ref. [13]. In the present paper we show that the general Lyapunov analysis can be extended to stationary plasmas surrounded by resistive walls even if their resistivity is time-dependent as investigated in Ref.…”

Section: Introductionsupporting

confidence: 56%

Lyapunov stability of flowing magnetohydrodynamic plasmas surrounded by resistive walls

Tasso

Throumoulopoulos

2011

Physics of Plasmas

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A general stability condition for plasma-vacuum systems with resistive walls is derived by using the Frieman Rotenberg lagrangian stability formulation [Rev. Mod. Phys. 32, 898 (1960)]. It is shown that the Lyapunov stability limit for external modes does not depend upon the gyroscopic term but upon the sign of the perturbed potential energy only. In the absence of dissipation in the plasma such as viscosity, it is expected that the flow cannot stabilize the system.

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Section: Introductionsupporting

confidence: 56%

Lyapunov stability of flowing magnetohydrodynamic plasmas surrounded by resistive walls

Tasso

Throumoulopoulos

2011

Physics of Plasmas

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“…Finally, the recent review of M.S.Chu and M. Okabayashi [3] is recommended as a nice and detailed survey of RWM stabilization technique.…”

Section: Conclusion and Discussionmentioning

confidence: 99%

“…The control of this instability was also the subject of a very comprehensive review by Chu and Okabayashi [3] two years ago. Here, we attempt to present a concise review of resistive wall mode physics, focusing on the mechanisms behind the mode behavior and only slightly touching on the control issues described in detail in Ref [3]. We start from the basic physics, focus on the recent achievements and discuss possible future steps.…”

Section: Introductionmentioning

confidence: 99%

Physics of resistive wall modes

Igochine

2012

Nucl. Fusion

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The advanced tokamak regime is a promising candidate for steady state tokamak operation which is desirable for a fusion reactor. This regime is characterized by a high bootstrap current fraction and a flat or reversed safety factor profile, which leads to operation close to the pressure limit. At this limit, an external kink mode becomes unstable. This external kink is converted into the slowly growing Resistive Wall Mode (RWM) by the presence of a conducting wall. Reduction of the growth rate allows one to act on the mode and to stabilize it. There are two main factors which determine the stability of the RWM. The first factor comes from external magnetic perturbations (error fields, resistive wall, feedback coils, etc). This part of RWM physics is the same for tokamaks and reverse field pinch (RFP)configurations. The physics of this interaction is relatively well understood and based on classical electrodynamics. The second ingredient of RWM physics is the interaction of the mode with plasma flow and fast particles. These interactions are particularly important for tokamaks, which have higher plasma flow and stronger trapped particle effects. The influence of the fast particles will also be increasingly more important in ITER and DEMO which will have a large fraction of fusion born alpha particles. These interactions have kinetic origins which make the computations challenging since not only particles influence the mode, but also the mode acts on the particles. Correct prediction of the "plasma-RWM" interaction is an important ingredient which has to be combined with external fields influence (resistive wall, error fields and feedback) to make reliable predictions for RWM behavior in tokamaks. All these issues are reviewed in this paper.2

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“…The relation between the external kink and the RWM with finite wall resistivity is reviewed in Ref. 4.…”

Section: Introductionmentioning

confidence: 99%

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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Stabilization of the external kink and the resistive wall mode

Cited by 200 publications

References 176 publications

Lyapunov stability of flowing magnetohydrodynamic plasmas surrounded by resistive walls

Lyapunov stability of flowing magnetohydrodynamic plasmas surrounded by resistive walls

Physics of resistive wall modes

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

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