Full wave field solutions and power conservation for the ion cyclotron range of frequencies (ICRF) in nonuniform plasmas

The subject of linear wave propagation and its associated power conservation in a slab geometry for waves in the ion cyclotron range of frequencies is treated. The governing differential equations and conservation relation are obtained using a Taylor series representation of the field evaluated to third order in the parameter, gyroradius/wavelength, which is assumed to be small for the cases examined here. This approach correctly incorporates the effects of transverse nonuniformity and is valid for all values of k∥. The local power conservation relation follows from a definition of local power absorption and a new companion general expression for kinetic flux based on fundamental principles. These expressions are evaluated to second order in gyroradius/wavelength in a numerical code, and results are presented for 3He fundamental minority and majority second harmonic cases. For fundamental minority 3He absorption, substantial reflection and mode conversion is found for lower parts of the k∥ spectrum with strong absorption, especially for the ion-Bernstein wave for k∥ >5 m−1. For second harmonic heating at higher 3He concentrations, strong absorption is found for lower values of k∥ with reduced reflection and mode conversion. For plasmas with substantial ion tail formation, tail absorption is found to dominate the absorption process with negligible mode conversion or reflections.