PIC Simulation of the Coherent Cerenkov– Cyclotron Radiation Excited by a High-Power Electron Beam in a Crossed-Elliptical Metamaterial Oscillator at S-Band

We present an S-band high-power microwave (HPM) oscillator based on crossed-elliptical metamaterial (MTM) rings in a circular waveguide and powered by a high-power electron beam. Particle-in-cell (PIC) simulations demonstrate that when an output horn antenna of radius of 200 mm is used, an output power of 443 MW of a backward wave TE
₄₁
mode below its cutoff frequency at 2.80 GHz can be generated using a pulsed electron beam with a voltage of 990 kV and a current of 1.736 kA in a 1.8-T solenoidal magnetic field, corresponding to an electronic efficiency up to 26%. Meanwhile, another degenerate frequency of 2.80 GHz of a forward wave in the TM
₀₁
mode with an output power of 9 MW is also observed. When an output horn antenna of radius 150 mm is used, this crossed-elliptical MTM oscillator operates mainly in a forward TM
₀₁
mode at 2.80 GHz with an output power of 325 MW at an electronic efficiency of 19%, and at the same time, a backward wave TE
₄₁
mode below its cutoff frequency of 2.80 GHz with an output power of 8 MW can be observed. Simulations indicate that this slow-wave structure (SWS) consisting of a periodically crossed-elliptical MTM loaded circular waveguide can support degenerate mode operation. This result suggests that this configuration is favorable for mode switching and this work seeks to design a compact HPM source.