Effect of Coulomb Collisions, Landau Damping and Particle Trapping on Linear and Nonlinear Ion Aooustic Waves.
Final rept. 12 Mar 92-31 Dec 95,
NORTHEASTERN UNIV BOSTON MA DEPT OF ELECTRICAL ENGINEERING
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The general propagator expansion method is used for the study of the collision effects and the Fokker-Planck kinetic equation is employed for several collisional processes. In drift-free plasma, the studies show that the plasma may become unstable if e-i collision growth can overcome Landau damping and other collision damping. The contamination can affect ion acoustic waves significantly and a small amount of light ion contamination can cause much higher damping. For our experiment on the ion acoustic waves in drift-free plasma, the experimental results are explained with the consideration of collision and contamination effects and are close to our theoretical results.For a plasma with a quasi-static electric field, two ion acoustic modes may propagate in a single ion species plasma. This ion-acoustic instability associated with the slow mode is a kinetic instability and is caused by the interaction of ions and electrons. In our experiment, the fast mode is found and the measured results agree with the theoretic values. In a two-on-species plasma, the velocity differences between the ion species can cause the ion-ion two-stream instability. This is a fluid instability and only exists in a range of ion drift velocities and wave frequencies. An experiment was performed to study ion-ion two-stream instability. The unstable waves generated by the ion beams are observed as predicted by theory and coincide with the kinetic dispersion relations for the ion-ion two stream instability.
- Plasma Physics and Magnetohydrodynamics