A High-Power, High-Efficiency S-Band Axial Vircator With Novel Waveguide Geometry

The VIRtual CAThode oscillatOR (circator) is a high-power microwave (HPM) source operating on the principle of virtual cathode formation and oscillation. The axial vircator is widely recognized for its simplicity, robustness, and wideband emission. However, its low efficiency remains a critical challenge, typically ranging between 0.1% and 1%. In this work, a novel high-power and high-efficiency S-band axial vircator is presented. The proposed geometry consists of a circular waveguide integrated with two semiconical and two semicylindrical structures near the diode to enhance power and prevent mode competition. To demonstrate the effectiveness of the proposed structure, the design of a vircator based on the novel waveguide with a single reflector has been designed. Particle-in-cell (PIC) simulations at 2.55 GHz shows an average output power higher than 350 MW and an efficiency of up to 3.36%, under an applied voltage of 520 kV and a cathode current of 20 kA, with an increase of 80 MW compared with a conventional single-reflector configuration under identical voltage and current conditions.