Efficiency Improvement Studies of Sub-Terahertz Multiwave Cherenkov Generator With a Coaxial Coupler

To increase the beam–wave interaction and coupling output efficiency, we propose a sub-terahertz multiwave Cherenkov generator (MWCG) with a coaxial coupler. The coaxial coupler is a partially open coaxial waveguide, which locates interiorly the second slow wave structure (SWS). Inside this region, the well-modulated electron beam interacts with the axial electric fields of the quasi-TEM mode and the coaxial TM
₀₁
mode simultaneously. Meanwhile, the radial electric fields of the two modes are efficiently coupled into the coaxial coupler and sufficiently extracted from the coaxial output waveguide. Particle-in-cell (PIC) simulations show that when the diode voltage is 203 kV and the beam current is 1.08 kA, the output power reaches 67.3 MW, corresponding to an efficiency of 30.6%, and the frequency is 338 GHz.