Generation of Ka-Band Superradiant Pulses for High-Gradient Acceleration of Electrons in a Scheme with Two Coaxial Beams

Millimeter-range generators of uniquely short (sub-nanosecond) GW-level Cherenkov superradiant (SR) pulses looks promising for high-gradient acceleration of electrons in non-superconducting metallic structures without the development of breakdown phenomena. In this paper, we propose the high-gradient acceleration scheme with two coaxial electron beams one of which (internal) is accelerated in a pillbox structure by a 250 ps/0.5 GW Ka-band SR pulse generated by the external beam due to interaction with the backward wave in periodical slow-wave structure. According to PIC simulations with parameters of the planning experiment, the accelerating gradient (rate of energy gain) in such a scheme can reach 350-400 MeV/m, which significantly exceeds characteristics of modern accelerators based on X-band klystrons.