Nonlinear theory for beam-wave interactions of two electron beams with higher order TE20 mode in serpentine waveguide traveling wave amplifier

Abstract

In this study, a nonlinear model is presented, which is used to analyze the beam-wave interaction of two electron beams with a higher TE20 mode in a serpentine waveguide (SW) traveling wave tube (TWT). Taking advantage of the novel model, the dimensions of SW are enlarged and the difficulties of fabrications of SW are reduced. To investigate the characteristics of two electron beams interacting with a high order mode in SW, the disk theory is used, in which the RF field in gap, space charge field, and the electron motion equations are combined, and the reactions of two electron beams to wave are considered. The nonlinear characteristics of power saturations, the distributions of electron velocity, and phase space are studied. To verify the validity of the nonlinear model, the theoretical results are compared with those of particle-in-cell simulations, and the output powers versus beam voltage and exciting frequency are studied. The results show that the relative errors are less than 10%, which are suitable for solving the SW-TWT operation characteristics.