EFFECTS OF ENERGETIC IONS ON KINETIC ALFVEN-WAVE IN A TOKAMAK PLASMA

The effects of energetic ions on the electric field structure and the energy deposition of kinetic Alfvén wave (KAW) in a tokamak plasma are considered. A cylindrical geometry is adopted and a linearized kinetic model including the bulk plasma and the energetic ions is established. These effects of fusion alpha particles (abbreviated, alphas) in deuterium-tritium (D-T) tokamak plasmas are numerically analyzed. The energetic ions tend to alter the wave structure and the energy deposition. The absorption of the kinetic Alfvén wave by the bulk plasma depends sensitively on both the velocity distribution of alphas and the spatial profile of the alpha particle density, as well as on the frequency of the injected wave. Numerical results of the wave structure and the power absorption are given for the parameters of D-T plasmas. The present studies lead to the following discoveries: (1) The slowing-down alpha particle distribution reduces the KAWs energy deposition and the Maxwellian alphas have hardly any influence over it; (2) the more the (slowing-down) alphas near the resonant layer, the more heavily they prevent the KAWs power absorption by the bulk plasma; (3) the lower frequency of the injected wave within the range of KAWs continuum, the more heavily the KAWs structure and power absorption by the bulk plasma are affected by alpha particles; and (4) the energy deposition decreases rapidly as the total number of alphas increases. © 1995 American Institute of Physics.