Effect of self-generated zonal flows on turbulent heat transport in a Tokamak plasma
A major goal in fusion research is understanding the anomalous thermal transport of energy and particles in a tokamak. In particular, a crucial issue is the origin of its empirical dependence on the various dimensionless parameters controlling the energy confinement. This paper addresses the impact of ion-ion collisions and of self-generated zonal flows (largescale ExB sheared poloidal flows) on turbulent ion thermal transport, in the core of a tokamak plasma. A three-dimensional fluid model is used, which describes flux-driven electrostatic plasma turbulence, generated by Ion Temperature Gradient (ITG) instabilities. The model includes curvature effects, parallel Landau damping and a collisional damping of the poloidal flows. Simulation results show a stabilization of the turbulence and a rise of the energy confinement time when the collisionality is lowered, that is when the zonal flows are weakly damped by ion-ion collisions. The mechanism responsible for the turbulence stabilization at low collisionality is identified as the non-linear upshift of the effective threshold for the ITG turbulence onset. This upshift is governed by an increase of the zonal flow shear.
Bibliographic Reference: Référence: Journal of Physics: Conference Series 7 (2005), p. 203-213
Availability: This article can be accessed online by subscribers, and can be ordered online by non-subscribers, at: http://dx.doi.org/10.1088/1742-6596/7/1/017
Record Number: 200518106 / Last updated on: 2005-04-25
Original language: en
Available languages: en