High-Power Microwave Generation by Excitation of a Plasma-Filled Rippled Boundary Resonator

An experimental demonstration of a strong enhancement of the interaction efficiency in a high-power relativistic backward-wave oscillator when plasma is injected is presented. Controlled plasma injection enhances the interaction efficiency for the vacuum case by a factor of up to eight to a value of about 40%. A linear theory of electromagnetic wave generation in plasma-loaded corrugated wall resonators is reviewed. A number of physical mechanisms are considered to account for the enhanced interaction, including two variations of a three-wave interaction involving the electron-beam slow space-charge wave, the slow electromagnetic waves in the structure, and the quasi-electrostatic waves in the plasma.