Erlangen 2018 – wissenschaftliches Programm
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P: Fachverband Plasmaphysik
P 7: Magnetic Confinement I - Helmholtz Graduate School III
P 7.3: Vortrag
Dienstag, 6. März 2018, 11:25–11:50, A 0.112
Quantitative study of kinetic ballooning mode theory in magnetically confined toroidal plasmas — •Ksenia Aleynikova1, 2, Alessandro Zocco1, Pavlos Xanthopoulos1, and Per Helander1 — 1Max-Planck-Institut für Plasmaphysik, EURATOM Association, Greifswald, Germany — 2MIPT, Dolgoprudny, Russian Federation
In this work, we report a systematic quantitative comparison of analytical theory and numerical gyro kinetic (GK) simulations of kinetic ballooning modes (KBMs) in a magnetically confined toroidal plasma. A physics-based ordering for plasma beta with small asymptotic parameters is found. This allows us to derive several simplified limits of previously known theories and to identify regimes where quantitative agreement between theory and numerical simulations can be achieved. For the axisymmetric case, in simple s-α geometry, it is found that, for large pressure gradients, the growth rate and frequencies computed by the gyrokinetic codes show excellent agreement with those evaluated by using, in the quadratic forms, a diamagnetic modification of ideal MHD. For moderate pressure gradients, a new finite-beta formulation of KBM theory is proposed.
The theory is also extended to treat the stellarator device W7-X. We show results of finite-beta electromagnetic GK simulations of KBMs for various W7-X configurations with different ideal MHD stability properties. This is important since, at present, it is not clear how the KBM and the ideal MHD ballooning mode thresholds relate to each other in stellarator geometry.