S-Band RF photoinjector as a driver for coherent Cherenkov source

Resonant Cherenkov radiation in capillary slow-wave structures driven by relativistic beams from a low-energy S-band photoelectron gun is considered. The generation of few megaelectron volt, sub-millimeter-sized, sub-ps microbunches is analyzed numerically. Different modes of operation of such an overfocused, high-current-density system with corresponding adaptation of RF photoinjector is discussed including some experimental measurements with beam on-cathode microbunching. Feasibility of generation of high peak power generation at terahertz frequencies is demonstrated with laser pulse multiplexing and photomixing.