Relativistic vircator with an electromagnetic bandgap medium

Summary form only given. The virtual cathode oscillator (vircator) can be one of the most promising high-power microwave sources due to its conceptual simplicity, high-output power capability, and potential tunability. Microwaves can be generated when the current of an intense relativistic electron beam exceeds the space-charge-limiting current of the structure. In this case, a virtual cathode comprising an electrostatic potential barrier is formed. Some of the electrons in the virtual cathode lose their kinetic energy and are then reflected back toward the anode. The energy conversion efficiency of the vircator is known to be very low (single digit). In this work, an electromagnetic band gap (EBG) material is investigated to increase the efficiency, to improve the tunability, and to extract the desired field structure at the output. The EBG structure follows a slot antenna concept, or more specifically, a leaky wave slot antenna. The slot array is cut at the waveguide wall to perturb the surface currents in a desired way. The fully electromagnetic, relativistic particle-in-cell (PIC) codes (MAGIC and CST-PS) and the fully electromagnetic software tool ANSYS-HFSS were used in this study.