Geodesic mode instability driven by electron and ion fluxes in tokamaks

0462525 - ÚFP 2017 RIV FR eng C - Conference Paper (international conference)
Elfimov, A.G. - Camilo de Souza, F. - Galvão, R.M.O. - Krbec, Jaroslav - Seidl, Jakub - Stöckel, Jan - Hron, Martin - Havlíček, Josef - Bogár, Klára
Geodesic mode instability driven by electron and ion fluxes in tokamaks.
EPS 2016: 43rd European Physical Society Conference on Plasma Physics. Vol. 40A. Mulhouse: European Physical Society, 2016 - (Mantica, P.; Giruzzi, G.; Fajardo, M.; Gans, T.; Poedts, S.; Vennekens, N.), č. článku P2.038. Europhysics Conference Abstracts (ECA), ECA, 40A. ISBN 2-914771-99-1.
[EPS 2016: Conference on Plasma Physics/43./. Leuven (BE), 04.07.2016-08.07.2016]
R&D Projects: GA ČR(CZ) GA16-25074S; GA ČR(CZ) GA14-35260S; GA MŠMT(CZ) LM2015045; GA MŠMT(CZ) 8D15001
Institutional support: RVO:61389021
Keywords : tokamak * COMPASS * GAM
Subject RIV: BL - Plasma and Gas Discharge Physics

Geodesic Acoustic Modes (GAM) are M=0, N=0 axisymmetric toroidal modes combined with M=±1, ±2 poloidal side-bands and driven by the electron and anisotropic ion pressure perturbations with the frequency \omega_G^2 = (7T_i/2+2T_e)/R_0^2m_i. These modes may be important for plasma transport as it has been theoretically discussed [2] and observed in experiments [4-7]. Furthermore, they may be useful as a diagnostic tool to indicate L-H confinement transition in tokamaks [5]. Eigenmodes in the geodesic frequency range have been experimentally detected under a wide range of conditions in various tokamaks. Typically, GAM oscillations are observed during counter NB injection [7,8], but they may also appear in ohmic discharges [6,8]. The nature of the experimentally observed geodesic eigenmodes is still not clear and several different mechanisms might be responsible for their dispersion and manifest themselves in different conditions. Recently, it has been theoretically shown that GAMs may be driven by an electric current with velocity along the equilibrium magnetic field in combination with the diamagnetic drift [3]. The instability occurs only when the electron current velocity is higher than the GAM phase velocity of sidebands, V_{e0}>Rq\omega
Here, we extend previous studies [3] and investigate whether the parallel plasma flow can drive the GAMs via coupling with the ion drift dynamics or/and the parallel current. Finally, comparison with NB experiments in COMPASS tokamak is discussed.




Permanent Link: http://hdl.handle.net/11104/0262217