Non-geometrical optics study of wave propagation

Heating of plasmas in large toroidal devices using electromagnetic waves with frequencies in the range of ion cyclotron resonance frequency is investigated in the case when in the resonance region the majority ions are in the second harmonic resonance and the minority ions are in the fundamental resonance. Particular attention is given to the case when the effects of the poloidal component of the equilibrium magnetic field significantly alter the wave propagation characteristics across the resonance region. The present study is the continuation of the previously studied cases of minority fundamental heating and the pure second harmonic heating by using ICRF waves. In all our previous analyses on ICRH we have assumed that the unperturbed particle distribution function was Maxwellian. This assumption was not required by our formulation, but the numerical study forced us to adopt a particular function to carry out the machine computations. It became evident in recent studies that under the influence of a strong ion cyclotron resonance heating, the minority ion distribution function is modified into a strongly anisotropic form by the generation of long tails associated with high energy ions created by this process at the resonant pitch angle. The effects of this anisotropy on the ICRF heating was not known. Recent investigations provide us with an analytic form for this distribution function. By making use of this function we have examined the effects of anisotropic distribution functions on ICRF heating. As a third problem we have also initiated a study on the problem of controlling the fusion generated high energy alpha ash by means of carefully prepared spatially anisotropic ICRF electromagnetic fields. We have carried out preliminary investigations restricted to the long-thin geometries, and demonstrated the relevancy of such a scheme. The extension of this study to general tokamak geometries with specified equilibrium flux surfaces is under consideration