Current drive by electron cyclotron waves in stellarators

Abstract

Electron cyclotron current drive studies in stellarators are justified for the potential the method holds in the control and compensation of unwanted, pressure-induced, plasma currents, as it has been shown experimentally in Wendelstain VII-AS stellarator [Fusion Technol. 17, 62 (1990)]. In this paper, a method is described to estimate induced currents by electron cyclotron waves that is computationally fast enough to be included in a ray-tracing code, but is able to account for the complicated stellarator geometry. In particular, the modification of the current drive efficiency due to trapped particles effects is included in the calculation. A close-to-Maxwellian electron distribution function and a nearly linear regime are assumed. An application of the method to the magnetic configuration of the TJ-II stellarator under construction in Madrid [Fusion Technol. 17, 131 (1990)] is also presented.