New opportunity of efficiency enhancement for FEL-oscillators

The FEL-twystron with self-exciting input and profiled amplifier output sections is suggested for realization of effective particle trapping and adiabatic deceleration in an oscillator regime. Such a scheme is especially attractive, when distribution of the RF field in the region between sections is smooth. This can be provided, in particular, by the use of distributed feedback in the input section. According to calculations, the proposed method allows a significant increase in efficiency for FEL-ubitrons and CARMs.