The generation of superradiance pulses by high-current subnanosecond electron bunches moving in a periodic slow-wave system: Theory and experiment

Cherenkov superradiance observed when an electron bunch rectilinearly moves through a slow-wave periodic system is studied theoretically and experimentally. The simulation based on averaged equations and the direct numerical simulation using the PIC-code KARAT show that the peak power of the microwave pulses varies as the total number of the particles in a bunch squared. This finding is confirmed experimentally. Ultrashort (300 ps wide) high-power (up to 140 MW) pulses are generated at a frequency of 39 GHz. As an electron source, the high-current subnanosecond RADAN-303 accelerator is used. It injects 0.5-to 1.5-ns-wide electron bunches of current up to 2 kA and energy 200–300 keV. The simulation suggests that the power of the electromagnetic pulses can be increased further (up to 300 or 400 MW) by optimizing the accelerating voltage pulse shape.