Competition between naturally excited and externally applied waves in the beam-plasma interaction

Variation of a naturally excited electron wave or waves by an externally launched wave is studied in electron beam-plasma systems, where the wave saturates due to a temperature broadening of beam. In a counter stream type, when the external wave suppresses the amplitude of a natural wave, the beam energy distribution function shows no appreciable change, and both waves complete with each other within a range that the total wave energy is not altered much. Equations describing this mode coupling for multimodes are similar to a gas laser system. In the case of single stream type, the energy distribution function is altered more by suppression. An approach is made to explain the suppression phenomenon of travelling waves. (author)