Speaker
Dr
Michael Leconte
(National Fusion Research Institute)
Description
Controlling Edge Localized Modes (ELMs) is very important for ITER, and a well-tested way to achieve this is by using external coils to generate Resonant Magnetic Perturbations (RMPs), demonstrated on several tokamaks [1-4]. The working hypothesis for the origin of ELM suppression is that RMPs increase transport in the pedestal, thus lowering the pressure-gradient below the ideal-MHD threshold. In this work, we show that - in presence of RMPS - Zonal Flows can drive a long-lived Vortex-Flow pattern. This finding clarifies the theory of RMP-induced Zonal Flow damping [5]. Note that evidence of such a Vortex-Flow pattern has been observed experimentally [6]. We obtain a dynamical system of coupled 1D equations for Zonal Flows and Vortex-Flow profiles, which we solve numerically (in our model, turbulence acts as a shear-dependent negative eddy-viscosity). As Zonal Flows are turbulence-driven, this shows that turbulence plays a major role in the plasma self-organization towards a 3D quasi-equilibrium. Contrary to Zonal Flows - which act as a benign reservoir of energy - the Vortex Flow pattern has a radial streamer-like flow associated to it and hence can drive convective transport. The associated enhancement in the particle transport - assuming the Vortex Flow has a density component - has a resonant character. This additional transport could act to limit the pressure-gradient, and is therefore a possible candidate to explain ELM suppression.
[1] T.E. Evans et al, Nucl. Fusion 48, 024002 (2008).
[2] Y. Liang et al, Phys. Rev. Lett. 98, 265004 (2007).
[3] W. Suttrop et al, Phys. Rev. Lett. 106, 225004 (2011).
[4] Y.M. Jeon et al, Phys. Rev. Lett. 109, 035004 (2012).
[5] M. Leconte, P.H. Diamond and Y. Xu, Nucl. Fusion 54, 013004 (2014).
[6] N. Vianello et al, Plasma Phys. Control. Fusion 57, 014027 (2015).
| Country or International Organization | Republic of Korea |
|---|---|
| Paper Number | TH/P3-27 |
Primary author
Dr
Michael Leconte
(National Fusion Research Institute)
Co-author
Dr
Juhyung Kim
(National Fusion Research Institute)
