Publication

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

Jonathan Graves, Wilfred Anthony Cooper, Daniele Brunetti, Alberto Mariani
2018
Journal Articles

Abstract

A new dispersion relation, and associated stability criteria, is derived for low-n external kink and infernal modes, and is applied to modelling the stability properties of quiescent H-mode like regimes. The analysis, performed in toroidal geometry with large edge pressure gradients associated with a local flattening of the safety factor, includes a pedestal, sheared toroidal rotation and a vacuum region separating the plasma from an ideal metallic wall. The external kink-infernal modes found here exhibit similarities with experimentally observed edge harmonic oscillations.

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https://infoscience.epfl.ch/entities/publication/163f237b-6d49-45b9-b042-71a590a5dcbe

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Jonathan Graves, Wilfred Anthony Cooper, Daniele Brunetti, Alberto Mariani
2018
Journal Articles

Abstract

Official source

https://infoscience.epfl.ch/entities/publication/163f237b-6d49-45b9-b042-71a590a5dcbe

About this result

Related concepts (32)

Stability theory

In mathematics, stability theory addresses the stability of solutions of differential equations and of trajectories of dynamical systems under small perturbations of initial conditions. The heat equation, for example, is a stable partial differential equation because small perturbations of initial data lead to small variations in temperature at a later time as a result of the maximum principle. In partial differential equations one may measure the distances between functions using Lp norms or the sup norm, while in differential geometry one may measure the distance between spaces using the Gromov–Hausdorff distance.

Plasma stability

The stability of a plasma is an important consideration in the study of plasma physics. When a system containing a plasma is at equilibrium, it is possible for certain parts of the plasma to be disturbed by small perturbative forces acting on it. The stability of the system determines if the perturbations will grow, oscillate, or be damped out. In many cases, a plasma can be treated as a fluid and its stability analyzed with magnetohydrodynamics (MHD).

Dispersion relation

In the physical sciences and electrical engineering, dispersion relations describe the effect of dispersion on the properties of waves in a medium. A dispersion relation relates the wavelength or wavenumber of a wave to its frequency. Given the dispersion relation, one can calculate the frequency-dependent phase velocity and group velocity of each sinusoidal component of a wave in the medium, as a function of frequency.

Related publications (11)

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

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Exploration of the parameter space for the excitation and saturation of Edge Harmonic Oscillations

On the relationship between the multi-region relaxed variational principle and resistive inner-layer theory

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