Excitation and suppression of asymmetrical modes in high frequency coaxial slow wave structures.

The interaction characteristics of quasi-TEM mode and EHv1 mode with an electron beam in coaxial slow wave structures (SWSs) are analyzed and compared in this paper. Through theoretical analysis and simulation verification, we find that the asymmetric EHv1 quasi-π mode has high external Q-factor, low starting current, and high temporal growth. It is almost impossible to suppress the EHv1 mode when using single section SWSs. In order to solve this problem, a feasible method is proposed in this paper to suppress the EHv1 mode effectively, under the premise that all modes cannot be exited in single section SWSs, introducing the feedback to ensure that the quasi-TEM mode operates effectively. [ABSTRACT FROM AUTHOR]