Excitation mechanism of standing waves produced by electron beam plasma instability

The excitation mechanism of standing waves produced by the electron beam plasma instability is experimentally studied using a Double Plasma device. When an electron beam is injected into the target plasma, standing waves around the electron plasma frequency are excited. A test wave is propagated in an electron beam plasma system and is identified as the beam mode from the dispersion relation. The propagation direction of the beam mode is determined from the wave pattern utilizing a phase shifter. It is found that a reflected beam mode exists as well as a forward beam mode, and is generated by the reflection of the forward beam mode from a potential well produced by the injection of the electron beam. The observed standing waves are formed by superposing the beam modes propagating in opposite directions from each other.