Powerful Relativistic Oscillators of THz-band based on Excitation of Talbot-type Supermode in an Oversized Cavity

For relativistic oscillators, a new interaction regime is proposed based on the excitation of not a fixed transverse mode of the cavity, but a supermode formed by a fixed set of transverse modes. Such regime is implemented in a quasi-optical cavity based on the Talbot effect, and allows narrow-band oscillation in a strongly oversized interaction space to be obtained. Simulations of THz-band FEL with sub-GW power level driven by high-current relativistic electron beam are discussed.