Collective Microwave Emission from Intense Elecron-Beam Interactions: Theory and Experiment

Abstract

High-power microwaves are observed in two clear frequency bands when an intense relativistic electron beam passes through an unmagnetized plasma. The high-frequency band has frequency which scales with ${\omega }_p$ and resembles radiation from processes in type-III solar bursts. Theory indicates beam-plasma stabilization may arise from radiative losses. The lower-frequency band, with frequency independent of ${\omega }_p$, may represent conversion of electrostatic waves near the plasma boundary in inhomogeneities of size ∼0.3 cm. Experiments in a magnetic field qualitatively agree with our models.