Coaxial multipactor with non-sinusoidal RF fields

This study investigates two-surface coaxial multipactor under non-sinusoidal Gaussian-type RF fields using 3D electromagnetic Particle in Cell simulations verified by 1D3V statistical simulations and numerical calculations. Gaussian-type RF fields increase both the threshold RF voltage and input RF power density for multipactor onset, with narrower Gaussian waveforms (smaller full width at half maximum) yielding higher thresholds. At low input RF power densities, Gaussian-type waveforms reduce the fraction of RF power loss due to multipactor. However, at higher input RF powers or near the upper boundary of the susceptibility band, Gaussian excitation expands the susceptible regime and increases RF power losses compared to sinusoidal excitation. The asymmetry in the deposited power densities on inner and outer conductors—an inherent feature of coaxial multipactor—becomes more pronounced, with Gaussian-type RF fields and larger aspect ratios. These results highlight the importance of tailoring waveform shape to the operational regime and demonstrate that Gaussian-type excitation offers a promising, yet regime-sensitive, strategy for multipactor suppression in high-power coaxial RF systems.