Heating and current drive by high intensity, pulsed, electron cyclotron Gaussian beams

Inspired by the experiments in the Microwave Tokamak Experiment (MTX) in the early 1990s, and the theoretical studies associated with these experiments, we have been studying the nonlinear relativistic interaction of electrons with high intensity, pulsed, Gaussian beams in the electron cyclotron range of frequencies. The Gaussian beam is analytically constructed so as to satisfy the full complement of Maxwell's equations for a cold, magnetized plasma. For electrons interacting with the beam, the components of the electron momentum, along and across the magnetic field, vary with the power and the direction of propagation of the beam. There are two effects that lead to changes in the momenta of electrons -- the ponderomotive force due to the spatial variation of the beam, and transit time interaction, including trapping, as electrons traverse the beam. We consider both the ordinary and the extraordinary waves and find that the wave polarizations lead to different dynamics of the electrons. There is no saturation of the momenta as the beam power is increased. The interaction of electrons with a beam is distinctly different from their interaction with a plane wave. Results for the gain in energy and momentum of the electrons as a function of beam parameters will be presented.