Combined generator–accelerator scheme for high-gradient electrons acceleration by Ka-band subnanosecond superradiant pulses

An increase in the accelerating gradient in hollow metal structures powered by an RF field is associated with the development of sources of high-power short-pulse high-frequency radiation. To date, the most powerful (multi gigawatts) nanosecond-scale microwave pulses are produced based on the effect of Cherenkov super-radiance (SR). We consider the possibility of experimental observation of high-gradient acceleration of electrons by Ka-band SR pulses in a combined generator–accelerator scheme with two coaxial electron beams formed by a single cathode. The outer tubular beam is used to generate the SR pulse in periodical slow-wave structure, while the inner one is accelerated in a “pill-box” resonator. The main parameters of the proposed scheme are determined based on full-scale particle-in-cell simulations, according to which accelerating gradient can reach 400 MV/m as some fraction of electrons passing the resonator increases energy from 250 keV to 1.85 MeV. Using the obtained data, injector of the coaxial beams and the sensor of accelerated electrons are developed and tested.