Nonlinear Stability and Saturation of Ballooning Modes in Tokamaks

C. J. Ham; S. C. Cowley; G. Brochard; H. R. Wilson

doi:10.1103/PhysRevLett.116.235001

Nonlinear Stability and Saturation of Ballooning Modes in Tokamaks

C. J. Ham, S. C. Cowley, G. Brochard, H. R. Wilson

Fusion Energy Division

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20 Scopus citations

Abstract

The theory of tokamak stability to nonlinear "ballooning" displacements of elliptical magnetic flux tubes is presented. Above a critical pressure profile the energy stored in the plasma may be lowered by finite (but not infinitesimal) displacements of such tubes (metastability). Above a higher pressure profile, the linear stability boundary, such tubes are linearly and nonlinearly unstable. The predicted saturated flux tube displacement can be of the order of the pressure gradient scale length. Plasma transport from these displaced flux tubes may explain the rapid loss of confinement in some experiments.

Original language	English
Article number	235001
Journal	Physical Review Letters
Volume	116
Issue number	23
DOIs	https://doi.org/10.1103/PhysRevLett.116.235001
State	Published - Jun 9 2016

Funding

This work has received funding from the European Union's Horizon 2020 research and innovation program, Grant No. 633053, and from the RCUK Energy Programme (Grant No. EP/I501045). The views and opinions expressed herein do not necessarily reflect those of the European Commission. H.R.W. acknowledges the Royal Society's Wolfson Merit Award scheme.

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10.1103/PhysRevLett.116.235001

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abstract = "The theory of tokamak stability to nonlinear {"}ballooning{"} displacements of elliptical magnetic flux tubes is presented. Above a critical pressure profile the energy stored in the plasma may be lowered by finite (but not infinitesimal) displacements of such tubes (metastability). Above a higher pressure profile, the linear stability boundary, such tubes are linearly and nonlinearly unstable. The predicted saturated flux tube displacement can be of the order of the pressure gradient scale length. Plasma transport from these displaced flux tubes may explain the rapid loss of confinement in some experiments.",

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AB - The theory of tokamak stability to nonlinear "ballooning" displacements of elliptical magnetic flux tubes is presented. Above a critical pressure profile the energy stored in the plasma may be lowered by finite (but not infinitesimal) displacements of such tubes (metastability). Above a higher pressure profile, the linear stability boundary, such tubes are linearly and nonlinearly unstable. The predicted saturated flux tube displacement can be of the order of the pressure gradient scale length. Plasma transport from these displaced flux tubes may explain the rapid loss of confinement in some experiments.

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Nonlinear Stability and Saturation of Ballooning Modes in Tokamaks

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