Direct Observation of Strong Wave/Particle Interactions in Electron-Beam Driven Plasma Wave Bursts

We present detailed observations of bursting wave behavior driven by an electron beam in a laboratory plasma, including high-time-resolution measurements of the wave bursts' disruption of the electron beam. Burst of wave activity are observed when a threshold electron beam density relative to the background plasma density is exceeded. Wave burst varying in their time duration are observed, but the fundamental structure of the bursts appears to be structures with a symmetric time envelope. Wave amplitudes large enough to disrupt the electron beam, substantially heat the beam, and eventually trap beam electrons at the phase speed of the waves are observed. By the experimental conditions and the behavior of the waves, we identify the electron acoustic mode as the type of waves we observe. The laboratory results are applicable to a variety of conditions in space plasmas.