Mechanism of radio frequency breakdown on metal surfaces in relativistic backward wave oscillator.

Radio frequency (RF) breakdown can result in pulse shortening and severely limits the performance of the relativistic backward wave oscillator (RBWO). In this study, segmented slow-wave structure (SWS) rings, which can be observed directly using a scanning electron microscope without any post-processing, are used to study the breakdown in a RBWO. After undergoing high-power microwave experiments, the working surface of the SWS rings was found to exhibit corrugated morphologies at the sub-mm to mm scale, and a large number of craters in the vicinity of the corrugated morphologies and a mass of scattered droplets were visible on the surface. It was deduced that the unusual morphologies resulted from electron bombardment of the working surface. The observed structures and droplets provide new evidence that helps to explain the mechanism for RF breakdown in the RBWO. [ABSTRACT FROM AUTHOR]