Microinstability theory of the two-energy component fusion plasma system

The stability theory for the two-component system is developed from the Vlasov-Maxwell equations. Several modes of microinstability which are associated with neutral beam injection or alpha particle production in fusion reactions are studied using three different models for the fast ion distributions. First, the fast ion distribution function arising from neutral beam injection is found from solutions of the Fokker-Planck equation. It is found that for pulsed parallel injection, the l = -1 ion cyclotron mode has a low threshold density due to Tb/sub perpendicular//E/sub b/ anisotropy. However, anomalous scattering of the wave is shown to enhance the diffusion of the fast ions in the nu/sub perpendicular/-direction, which will stabilize the system in a small fraction of the slowing down time when l = -1 mode is dominant. The second form of the fast ion distribution arising from parallel and anti-parallel injections is modeled by a counter-streaming Bi-Maxwellian and it is shown that the left-handed circularly polarized mode has negligible thermal ion and electron damping effects. Another form of the fast ion distribution is formed either from multi-directional neutral beam injections, or from energetic alpha particles from the fusion reactions. Except for the drift wave, which is either unstable or near marginal stability, no significant instabilities occur for this distribution at small eta/sub b//eta/sub e/