Role of infernal modes dynamics and plasma rotation on the onset of NTMs in ECH-ECCD TCV plasmas

Joint Varenna-Lausanne International Workshop on the Theory of Fusion Plasmas 2016

Brunetti, D.^1 ; Lazzaro, E.^1 ; Nowak, S.^1 ; Sauter, O.^2 ; Graves, J.P.^2

Istituto di Fisica Del Plasma IFP-CNR, Via R. Cozzi 53, Milano

20125, Italy^1

École Polytechnique Fédérate de Lausanne (EPFL), Swiss Plasma Center (SPC), Lausanne

CH-1015, Switzerland^2

关键词: Current density profiles;    Electron cyclotron heating;    Finite-beta effects;    Plasma core regions;    Possible mechanisms;    Stability indices;    Stability parameters;    Toroidal plasma rotation;   

Others  :  https://iopscience.iop.org/article/10.1088/1742-6596/775/1/012002/pdf
DOI  :  10.1088/1742-6596/775/1/012002

来源: IOP

【 摘 要 】

Experiments in the TCV tokamak show that when high power central electron cyclotron heating (ECH) and current drive (ECCD) are deposited in the central plasma region, tearing-like instabilities can develop. In the present work we address, both analytically and numerically, the problem of tearing mode (TM) generation analysing extensively the behaviour of L-mode and low plasma current TCV discharges when high power heating is deposited in the plasma core region. Three possible mechanisms are discussed. The first is the modification of the equilibrium current density profile due to the power deposition leading to variation of the sign of the classical tearing stability index Δ', where finite β effects could also be taken into account. The second mechanism still the modification of the tearing stability parameter Δ', but this time due to the presence of an equilibrium sheared toroidal plasma rotation. Finally, the third mechanism considered is the role of infernal-type instabilities in driving tearing-like modes when the safety factor becomes sufficiently close to a rational in the core region.