| The stability of both Global Alfven eigenmodes and Kinetic Alfven Waves in the presence of energetic Alpha particles produced in the fusion reactions, is studied analytically and numerically. The basic eigenmode equations describing the responses of electrons, thermal ions, and Alpha particles driven by Alfven wave perturbations are constructed using a linearized kinetic model in cylindrical geometry.;Both Global Alfven Eigenmodes and Kinetic Alfven Waves, with small parallel wave numbers, are found to be unstable to the plasma parameters relevant to the later phase operation of T.F.T.R.Tokamak. Global Alfven Eigenmode with toroidal model and poloidal mode numbers (1,m) = (0,-2) is identified as the most dangerous mode, remains unstable for fairly broad range of possible Alpha particle distributions. The growth rates of Kinetic Alfven Waves are fairly sensitive to the models used for finite gyroradius effect of Alpha particles and are easily stabilized by either broadening the radial distribution or lowering the temperature of the Alpha particles.;The problems of heating and current drive using Compressional Alfven Waves are then examined. The Alpha particles interact strongly with the Compressional Alfven Waves with phase velocities closed to the thermal velocities of the Alpha particles, via transit time magnetic pumping, resulting substantial energy absorption by Alpha particles. The usual current drive scheme using low phase velocity Compressional Alfven Waves cannot avoid this Alpha particle absorption. A high phase velocity current drive scheme using Compressional Waves with K(,(theta)) >> k(,(zeta)) (k(,(theta)) and k(,(zeta)) are the poloidal and toroidal wave numbers), is proposed and the new scheme can avoid both Alpha particle absorption and edge heating due to Alfven resonance absorption.;The model includes important kinetic effects such as finite elec- tron mass and finite ion gyroradius, which lead to Landau damping and formation of Kinetic Alfven Waves inside the Alfven continuum. In addition, equilibrium current density gradient, magnetic shear and finite (omega)/(omega)(,ci) effects are incorporated, providing the conditions for the formation of Global Alfven Eigenmodes below the Alfven continuum. The response of the Alpha particles is manifested as additional perturbed current due to the large equilibrium drifts of the particles. |
