Interaction of high-power microwaves with plasma in a corrugated wall waveguide

Plasma-filled backward wave oscillators utilizing IREBs have demonstrated the efficiency enhancement up to 40%. Botton and Ron suggested that the high efficiency could be explained by a self-induced distributed feedback mechanism of a density grating formed by ponderomotive potential of backward and forward waves in the slow wave structure. We carried out an experiment to detect such plasma grating formed by high-power externally injected microwaves. In contrast to Botton and Ron's prediction, results indicate that electrons are selectively excluded from the positions R(z) minima assuming that the plasma is non-neutral. Supersonic ion flow in neutral plasma toward the cathode stagnates at R(z) minima.