Current drive by EC waves in the presence of magnetic islands and transport

Abstract

In this paper we address the problem of current drive by electron cyclotron (EC) waves in the presence of magnetic islands and transport. Our approach makes use of quasilinear theory by numerically solving the Fokker–Planck equation in cylindrical geometry. We take into account the actual geometry of the islands along the calculations as well as the changes in the plasma density profile due to the action of the radial particle transport. The particle transport is supposed to have a magnetic origin. The waves are assumed to be launched and propagated in the equatorial plane of the tokamak, as in the slab geometry. Our results show that the use of equilibrium profiles as usually done in the studies on neoclassical tearing mode control may not be a better choice and point to the need for taking into account the actual island geometry.