An X-band Standing Wave Dielectric Loaded Accelerating Structure

An 11.4 GHz standing wave Dielectric Loaded Accelerating (DLA) structure was recently developed. The structure is designed to achieve a 120 MV/m gradient powered by a 10 MW 200 ns rf pulse from the X-band Magnicon at the Naval Research Laboratory (NRL). The structure uses on-axis rf coupling, which helps to localize the maximum EM fields within the dielectric region. Bench testing shows excellent agreement with the simulation results. In the high power rf test, multipactor was found to prevent increasing the gradient inside the dielectric cavity beyond 10MV/m. A simple model has been constructed that shows good agreement with the experiment. A new approach to completely suppress the multipactor in DLA structures using an axial magnetic field has been proposed. More experiments are planned.