The interaction of charged particle beams with plasma

Abstract

Interaction of charged particles with plasma plays an important role in the various discharges in the experimental devices used for the study of controlled thermo nuclear reactions. This interaction must be known in order to solve the problems lnvolving acceleration of particles. and generation and amplification of microradiowaves by the plasma. In spite of the apparent differences in the types of interaction, at the basis of the processes lies the VavilovCherenkov effect, the anomalous and normal Doppler effect, and the polarization of the plasma by the movement of the charged particles. The instabilities due to these factors are tabulated. Instabilities may arise at relatively low electron velocities. The periods of confinement of the plasma are in many cases longer than the times of growth of the instability, indicating that not all the listed instabilities play equally important roles. In spite of relatively successful theoretical work and related experimental proof, not all the instabilities arising in discharge phenomena can be predicted. This is due to the fact that in most cases only the excitation spectra are known while the amplitude of the exciting wave remains undefined. With increasing amplitude many non-linear effects which weaken the instability increase also. Most of themore » instabilities predicted by the theory have been observed experimentally and the basic characteristics, such as conditions of excitation, growth increments, frequency spectrum, and relaxation length agree well with the theory but much work remains to be done. (TTT)« less