ULTRAHIGH-POWER FREE-ELECTRON LASERS WITH 2-DIMENSIONAL DISTRIBUTED-FEEDBACK

Two-dimensional distributed feedback is proposed in order to obtain a spatially-coherent radiation of ribbon relativistic electron beams (RE B) with transverse dimensions several orders of magnitude larger than the radiation wavelength. The feedback is provided by means of a two-d imensional Bragg resonator. The resonator consists of two metal plates with biperiodically corrugated side walls, the plates being parallel to the beam. The transverse electromagnetic energy flows arising in th e resonator serve to synchronize the radiation emitted by individual b eam segments. The resonator eigenmodes are found. The selective proper ties of the resonator are also studied. The excitation process of the 2-D Bragg resonator was computer simulated. The simulation results sho w the possibility of obtaining a coherent single mode generation using a ribbon electron beam with transverse dimensions on the order of (10 (2) - 10(3)) wavelengths. The concept of an ultrahigh-power millimeter -range free-electron laser (FEL) of 20 GW output power is presented. A ribbon REB 140 cm in width produced by the U-2 accelerator (Budker Nu clear Physics institute, Russian Academy of Sciences, Siberian Divisio n, Novosibirsk) is proposed for FEL pumping.