Free-Electron Masers Based on Excitation of Talbot-Type Supermodes

In powerful THz electron maser based on the use of a high-current relativistic electron beam, the use of an oversized cavity it inevitable. In this situation, it is difficult to provide selective excitation of a definite operating cavity mode. We propose to use excitation of a supermode formed by a fixed set of several transverse modes of an oversized waveguide due to the Talbot effect. We present designs of THz-frequency-range free-electron masers fed by a 10 MeV / 2 kA / 200 ns electron beam and based on excitation of a Talbot-type supermodes. The presentation includes results of our multi-frequency multi-mode simulations of the electron-wave interaction during the spatio-temporal process of formation and amplification of the supermode in oversized microwave systems. The calculated efficiency of these FEMs at the level of 5-10% corresponds to the GW level of the output power