Field-line localized destabilization of ballooning modes in 3D tokamaks

Abstract

Field-line localized ballooning modes have been observed at the edge of high confinement mode plasmas in ASDEX Upgrade with rotating 3D perturbations induced by an externally applied n = 2 error field and during a moderate level of edge localized mode-mitigation. The observed ballooning modes are localized to the field-lines which experience one of the two zero-crossings of the radial flux surface displacement during one rotation period. The localization of the ballooning modes agrees very well with the localization of the largest growth rates from infinite-n ideal ballooning stability calculations using a realistic 3D ideal magnetohydrodynamic equilibrium. This analysis predicts a lower stability with respect to the axisymmetric case. The primary mechanism for the local lower stability is the 3D distortion of the local magnetic shear.

arXiv comment11 pages, 5 figures, for submission to Physical Review Letter

References in corpus (6)

• Effect of resonant magnetic perturbations on low collisionality discharges in MAST and a comparison with ASDEX Upgrade
• Non-linear modeling of the plasma response to RMPs in ASDEX Upgrade
• Plasma response measurements of external magnetic perturbations using electron cyclotron emission and comparisons to 3D ideal MHD equilibrium
• Towards understanding edge localised mode mitigation by resonant magnetic perturbations in MAST
• A model for microinstability destabilization and enhanced transport in the presence of shielded 3-D magnetic perturbations
• Three dimensional boundary displacement due to stable ideal kink modes excited by external n=2 magnetic perturbations

Cited by in corpus (5)

• Experimental conditions to suppress edge localised modes by magnetic perturbations in the ASDEX Upgrade tokamak
• The Density Dependence of Edge-Localized-Mode Suppression and Pump-out by Resonant Magnetic Perturbations in the DIII-D Tokamak
• Plasma Performance and Operational Space without ELMs in DIII-D
• Optimizing beam-ion confinement in ITER by adjusting the toroidal phase of the 3-D magnetic fields applied for ELM control
• Operational Space and Plasma Performance with an RMP-ELM Suppressed Edge