Normal Modes in the Ion-Beam-Plasma System

Abstract

Two types of dispersion relations are experimentally shown to exist in an ion-beam-plasma system. For beam velocities close to the ion-sound speed, two normal modes, one unstable, are seen. For larger beam velocities, the interferometer output exhibits beating between the three predicted stable normal modes, which are the "fast" and "slow" ion-beam modes and the plasma ion-acoustic wave.