A study of beam-plasma discharge (1)

Characteristics of hot electron plasmas produced by beam-plasma discharge are investigated both experimentally and theoretically. The experimental results on excited waves, self-sustained conditions, hot electron production mechanism and diffusion process of charged particles are compared with the theoretical predictions. Ion plasma waves are found to be excited in such a plasma due to a coupling with slow cyclotron waves of the electron beam. Electron hybrid wave interaction with beam slow waves becomes essential in its burnout state. Self-sustained conditions of this discharge are determined in its parameter space. Production mechanism of hot electrons is examined from energy measurement of radiated X-ray, which gives a possible evidence of electron cyclotron heating in this RF discharge. Diffusion of charged particles (cold electrons) obeys ambipolar theory in quiescent plasma state, but in turbulent plasmas diffusion tends to occur with large diffusion coefficient beyond classicas values, which is presumably due to anomalous enhancement of apparent collision frequencies. (author)