A self-consistent theory of Thonemann's current drive experiment

Summary form only given. Current drive is conventionally viewed as the selective pushing of electrons or ions in a plasma by means of plasma waves or neutral beams. A new point of view has emerged in some recent studies, which treat the steady-state current as a macroscopic characteristic of the plasma. In these schemes, steady-state current is produced as a result of nonlinear mixing of linear waves inside the plasma. These schemes have the advantage that the bulk of the plasma participates in the current production process. These ideas, however, remain experimentally untested as yet. In this paper, we explore this nonlinear wave mixing process in a plasma and antenna configuration that is very similar to the one in Thonemann's classic current drive experiment. It is shown that many of the essential features of the experiment can be explained using the idea of nonlinear wave mixing. We also discuss extensions of the model that apply to larger and warmer plasmas. The geometry of the problem consists of a slab of unmagnetized plasma surrounded by a pair of electric current sheet antennas. It is assumed that the plasma is fully ionized and is governed by two fluid equations. The external antennas generate a first order traveling wave inside the plasma. The excited wave is electromagnetic and is characterized by an evanescent perpendicular profile at low frequencies.