Effect of radial electric boundary potential on a circular cylindrical magneto plasma, 2

This paper is described on the effects of oscillating potential in square form on the system of electron beam and plasma and on the wave due to two counter-streaming electron beams. Neutral nitrogen gas was injected into an interaction chamber. The Langmuir probe was used for the measurements. An electron gun supplied electron beam. A field coil gives a magnetic field parallel to the axis of the cylinder. The oscillation was observed, which is inferred to have arisen from the interaction between the slow plasma waves of the electron beam and the cyclotron waves of the plasma. When the square wave potential was supplied, the shift to the low frequency side was seen. The shift depends linearly on the supplied voltage. In a two-beam system, the strongest and most easily observable line in the system is the oscillation which is due to the instability raised by the interaction between the slow plasma waves on the forth-streaming beam and the fast cyclotron waves on the counter-streaming beam. It can not bring about the frequency shift, but only depresses the line intensity without increasing very much the line width. The frequency shift must be closely related to the diffusion of charged particles in the plasma generated by beam. (Kato, T.)