Electron rf Oscillator Based on Self-Excitation of a Talbot-Type Supermode in an Oversized Cavity

We propose the concept of selective excitation of a terahertz operating wave in a high-power electron maser with an oversized microwave system fed by a high-current relativistic electron beam. This concept is based on excitation of a supermode formed by a fixed set of transverse modes, rather than a fixed transverse mode of the operating cavity. A possible approach to form a high-Q supermode inside a simple cavity is the use of the Talbot effect, namely, periodic reproduction of the transverse structure of a multimode wave field in an oversized waveguide.