Analytic stability criteria for edge MHD oscillations in high performance ELM free tokamak regimes

Brunetti, D.; Graves, J. P.; Lazzaro, E.; Mariani, A.; Nowak, S.; Cooper, W. A.; Wahlberg, Christer

doi:10.1088/1741-4326/aa9456

Cited by 12 publications

(77 citation statements)

References 28 publications

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“…In addition, as shown in Brunetti et al (2018) in the ideal wall case, the mode stability properties are not altered by a subsonic toroidal flow. Therefore we shall infer that the toroidal rotation alone is not sufficient to explain why in the experiments only a single n dominant mode is observed (see e.g.…”

Section: Discussionmentioning

confidence: 63%

Analytic study on low- external ideal infernal modes in tokamaks with large edge pressure gradients

Brunetti

Graves²,

Lazzaro

et al. 2018

J. Plasma Phys.

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The problem of pressure driven infernal type perturbations near the plasma edge is addressed analytically for a circular limited tokamak configuration which presents an edge flattened safety factor. The plasma is separated from a metallic wall, either ideally conducting or resistive, by a vacuum region. The dispersion relation for such types of instabilities is derived and discussed for two classes of equilibrium profiles for pressure and mass density.

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Section: Discussionmentioning

confidence: 63%

Analytic study on low- external ideal infernal modes in tokamaks with large edge pressure gradients

Brunetti

Graves²,

Lazzaro

et al. 2018

J. Plasma Phys.

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“…In this Letter the specific physical mechanisms which allow low-n EHOs to emerge are identified by extending the analysis of Ref. [25] within the infernal model framework. Features of both external kink and infernal modes are required, viz.…”

mentioning

confidence: 89%

“…The rotational transform profile (denoted with µ with q = 1/µ) is piecewise continuous [25], constant for 0 < r < r 0 and r 1 < r < r p (r p = (r 1 + a)/2), with values µ ax and µ 1 respectively (µ…”

Section: Is the Ion Mass) Are The Plasma Mhd And Ion Diamagnetic Velomentioning

confidence: 99%

“…In the inner and outer regions, because of field line bending dominating over inertia and vanishing pressure gradients, different poloidal Fourier harmonics behave independently according to [25,33] (here = m, m ± 1 and ≡ d/dr):…”

Section: Is the Ion Mass) Are The Plasma Mhd And Ion Diamagnetic Velomentioning

confidence: 99%

“…The equation for the generic radial displacement ξ is obtained by applying the operator D = √ g∇ϕ • ∇ × 1/B ϕ 0 on the perturbed momentum equation [35,36], and then selecting the th Fourier component. Field line bending dominates over inertia in the sidebands equations (modes with poloidal mode number m ± 1), so that additional flow effects play no role in their corresponding eigenmode equations which read [25]:…”

Section: Is the Ion Mass) Are The Plasma Mhd And Ion Diamagnetic Velomentioning

confidence: 99%

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Excitation Mechanism of Low- n Edge Harmonic Oscillations in Edge Localized Mode-Free, High Performance, Tokamak Plasmas

et al. 2019

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The excitation mechanism for low-n Edge Harmonic Oscillations in quiescent H-mode regimes is identified analytically. We show that the combined effect of diamagnetic and poloidal MHD flows, with the constraint of a Doppler-like effect of the ion flow, leads to the stabilisation of short wavelength modes, allowing lown perturbation to grow. The analysis, performed in tokamak toroidal geometry, includes the effects of large edge pressure gradients, associated with the local flattening of the safety factor and diamagnetic flows, sheared parallel and E × B rotation and a vacuum region between plasma and the ideal metallic wall. The separatrix also is modelled analytically.

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Resistive stability of cylindrical MHD equilibria with radially localized pressure gradients

et al. 2019

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As a step toward understanding 3D magnetohydrodynamic (MHD) equilibria, for which smooth solutions may not exist, we develop a simple cylindrical model to investigate the resistive stability of MHD equilibria with alternating regions of constant and nonuniform pressure, producing states with continuous total pressure (i.e., no singular current sheets) but discontinuities in the parallel current density. We examine how the resistive stability characteristics of the model change as we increase the localization of pressure gradients at fixed radii, which approaches a discontinuous pressure profile in the zero-width limit. Equilibria with continuous pressure are found to be unstable to moderate/high-m modes and apparently tend toward ideal instability in some cases. We propose that additional geometric degrees of freedom or symmetry breaking via island formation may increase the parameter space on which equilibria of our model are physically realizable, while preserving the radial localization of pressure gradients. This is consistent with the possibility of realizing, in practice, 3D MHD equilibria which support both continuously nested flux surfaces (where rp 6 ¼ 0) and chaotic field regions (where rp ¼ 0).

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Analytic stability criteria for edge MHD oscillations in high performance ELM free tokamak regimes

Cited by 12 publications

References 28 publications

Analytic study on low- external ideal infernal modes in tokamaks with large edge pressure gradients

Analytic study on low- external ideal infernal modes in tokamaks with large edge pressure gradients

Excitation Mechanism of Low- n Edge Harmonic Oscillations in Edge Localized Mode-Free, High Performance, Tokamak Plasmas

Resistive stability of cylindrical MHD equilibria with radially localized pressure gradients

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