Growth and Damping of Wave-Particle Interactions in Counterstreaming Electron Beams

Abstract

Experimental observations have been made of wave-particle interactions in counter-penetrating electron beams in a static magnetic field. A new technique is used to measure the electron-distribution function at every stage of wave growth, saturation, and decay. The particular instability discussed here occurs at one half the cyclotron frequency and has a density threshold for onset. As the wave grows, trapping of resonant particles in the wave-potential troughs becomes significant and the velocity distribution is appreciably broadened. Finally, "finite-temperature" stabilization prevails and the wave decays. The experimentally observed resonance width is in agreement with the predictions of strong turbulence theory.