Speaker
Prof.
Evgeniy Gusakov
(Ioffe Institute)
Description
In this paper the trapped electron mode turbulence and ExB flows are investigated in hydrogen and deuterium Ohmic FT-2 tokamak plasmas experimentally by a set of microwave Doppler backscattering diagnostics and numerically by the global gyrokinetic ELMFIRE code. The plasma poloidal velocity associated with GAMs is shown to be larger than the mean flow velocity, thus possessing a strong impact on the ExB flow shear. The effective shearing manifests itself as a modulation of the turbulence level and particle flux by the space-time GAM pattern. GAMs are modulating turbulence due to rotation shear and, in its turn, the modulated turbulence is pumping the GAM due to the Reynolds stress shear (RSS). The numerical analysis demonstrates the self-organized turbulent dynamics, when the pumping of the flow by the turbulence is found to be balanced by collisional damping. The GAM activity is shown, both in experiment and computation, to be more intensive in deuterium because of smaller damping in the case of heavier isotope. The RSS, the ExB flow and the particle flux oscillate close to in-phase in time, while the flow shear induced by GAMs follows with a phase shift of pi/2. This behavior is consistent with experimentally observed high coherency of turbulence level and plasma poloidal velocity dynamics at the GAM frequency.
Primary author
Prof.
Evgeniy Gusakov
(Ioffe Institute)
