Observation of an Obliquely Growing Mode in an Ion-Beam—Plasma System

Abstract
By use of a small launcher in an ion-beam—plasma system, a spatially growing mode, which propagates obliquely to the ion beam, was observed. With ion beams, the wave propagation vector was found to be not in the radial direction from the launcher. The observed phase velocity and spatial growth rate of a slow ion-beam—plasma mode are explained by three-dimensional wave theory.