Powerful Spatially-Extended Cherenkov Masers for Pumping Systems of Compton FELs

Conception of Compton-type FELs is under development currently at IAP RAS (Nizhny Novgorod). This concept is aimed at reducing energy of a driving relativistic electron beam and thereby increasing efficiency of the electron-wave interaction in FEL, as well as achieving relative compactness of the generator. The basis of this concept is RF-undulators of a new type - the so-called “flying” undulators. Present paper is devoted to design parameters and results of simulation of the Cherenkov maser intended for powering the RF-undulator of such type in the Ka-band. In order to achieve the required sub-gigawatt power level of the pumping wave in a strongly oversized oscillator, we exploit the original idea of using two-dimensional distributed feedback implemented in the 2D doubly-periodical slow-wave structures.