High-Power Spatially Extended Free-Electron Masers with Three-Dimensional Distributed Feedback

We study the possibility of using Bragg resonators that implement a three-dimensional distributed feedback mechanism ensuring synchronization of radiation and mode selection under conditions of substantial oversize in three spatial coordinates. To describe the electron–wave interaction in devices of this type, a three-dimensional spatiotemporal averaged model was developed within the framework of the coupled wave approach. On this basis, a planar free-electron maser (FEM) driven by a full-scale electron beam of a sheet configuration with a particle energy of 1 MeV, a current of up to 140 kA, and a cross section of about 1 × 140 cm, which is formed using a high-current accelerating complex U-2 (BINP RAS), was simulated. The possibility of achieving a stable narrow-band oscillation regime in FEMs with a multi-gigawatt power level in the W band with transverse sizes of the proposed resonators from tens to hundreds of radiation wavelengths is demonstrated.