Mechanism of neoclassical tearing modes triggering by a magnetic perturbation

Arcis, N.; Sharapov, S. E.

doi:10.1016/j.physleta.2008.07.028

Cited by 8 publications

(8 citation statements)

References 34 publications

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“…The fishbone instability is known to cause enhanced losses of energetic ions. It may also thwart confinement of the thermal plasma by initiating long-lasting kink and neoclassical tearing modes [76][77][78]. The fishbone bursts are oscillatory.…”

Section: The Fishbonesmentioning

confidence: 99%

“…It is also noteworthy that the excitation of NTM correlates with a change in the fishbones' period followed by suppression of fishbones after 29.05 s. However, the physics mechanism of the suppression is so far unclear. A theoretical model for the observed NTM triggering by fishbones was recently proposed in [78]. The fishbones can act on the NTM as an external magnetic perturbation that brings the frequency of the micro-tearing islands into the unstable zone via toroidicity-induced coupling.…”

Section: The Fishbonesmentioning

confidence: 99%

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Major minority: energetic particles in fusion plasmas

Breǐzman

Sharapov

2011

Plasma Phys. Control. Fusion

155

211

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This paper describes advances made in the field of energetic-particle physics since the topical review of Alfvén eigenmode observations in toroidal plasmas (Wong 1999 Plasma Phys. Control. Fusion 41 R1-R56). The development of plasma confinement scenarios with reversed magnetic shear and significant population of energetic particles, and the development of novel energeticparticle diagnostics were the main milestones in the past decade, and these are the main experimental subjects of this review. The theory of Alfvén cascade eigenmodes in reversed-shear tokamaks and its use in magnetohydrodynamic spectroscopy are presented. Based on experimental observations and nonlinear theory of energetic-particle instabilities in the near-threshold regime, the frequency-sweeping events for spontaneously formed phase-space holes and clumps and the evolution of the fishbone oscillations are described. The multimode scenarios of enhanced particle transport are discussed and a brief summary is given of several engaging research topics that are beyond the authors' direct involvement.

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Section: The Fishbonesmentioning

confidence: 99%

Section: The Fishbonesmentioning

confidence: 99%

Major minority: energetic particles in fusion plasmas

Breǐzman

Sharapov

2011

Plasma Phys. Control. Fusion

155

211

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“…It generally originates in a small magnetic island seeded by other types of instabilities or residual error field due to the asymmetry of the tokamak device [12][13][14][15]. As the size of the seed island is large enough to lead to the flattening of the pressure inside the separatrix of the island, the local reduction of the bootstrap current, which is proportional to the pressure gradient, can further destabilize and trigger the NTM [16,17]. Thus, the NTM is linearly stable, but can be nonlinearly destabilized by the change of pressure gradient, which is different from the classical tearing mode (TM) driven by the equilibrium radial current density gradient.…”

Section: Introductionmentioning

confidence: 99%

A brief review: effects of resonant magnetic perturbation on classical and neoclassical tearing modes in tokamaks

Wang

Tang

Lai

2022

Plasma Sci. Technol.

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This paper reviews the effects of resonant magnetic perturbation (RMP) on classical tearing modes (TMs) and neoclassical tearing modes (NTMs) from the theory, experimental discovery and numerical results with a focus on four major aspects: (i) mode mitigation, where the TM/NTM is totally suppressed or partly mitigated by the use of RMP; (ii) mode penetration, which means a linearly stable TM/NTM triggered by the externally applied RMP; (iii) mode locking, namely an existing rotating magnetic island braked and finally stopped by the RMP; (iv) mode unlocking, as the name suggests, it is the reverse of the mode locking process. The key mechanism and physical picture of above phenomena are revealed and summarized.

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“…Additional physics, coming for example from a two fluid description, could well be essential in the triggering process, allowing for example the polarization current to provide a destabilizing contribution. This could be the case if the seed mode has a frequency outside the range between electron and ion diamagnetic frequencies [31], as modelled in [32]. However, experimental investigations on the NTM triggering process remain difficult [33,34].…”

Section: Introductionmentioning

confidence: 99%

Modelling of (2,1) NTM threshold in JET advanced scenarios

Maget

Lütjens

Coelho³

et al. 2010

Nucl. Fusion

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The limit to high performances advanced scenario discharges with q min above unity is generally set by the (2,1) magneto-hydro-dynamic (MHD) mode in JET. We investigate here the possibility that this mode is a (2,1) neoclassical tearing mode (NTM) by computing the critical island width at which such mode would be unstable, using a nonlinear MHD code where the relevant bootstrap current physics is accounted for. We show that the triggering of a (2,1) NTM is consistent with a lowering of the critical island width as the plasma current diffuses towards the centre. This is explained partly by the increase in the magnetic shear at the resonant surface, which weakens the curvature stabilization term, as found in the analytical framework of a generalized Rutherford equation. A comparison with experiment is made in the non-linear regime, showing encouraging results on the dynamics of the confinement degradation and mode structure.

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Mechanism of neoclassical tearing modes triggering by a magnetic perturbation

Cited by 8 publications

References 34 publications

Major minority: energetic particles in fusion plasmas

Major minority: energetic particles in fusion plasmas

A brief review: effects of resonant magnetic perturbation on classical and neoclassical tearing modes in tokamaks

Modelling of (2,1) NTM threshold in JET advanced scenarios

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