Direct generation of a circularly polarized TE11 mode in a relativistic backward wave oscillator by loading anisotropic medium

Abstract

Abstract A relativistic backward wave oscillator (RBWO) for direct generation of a circularly polarized TE11 mode is proposed. Using a coaxially loaded anisotropic medium with an appropriate longitudinal conductivity, the TM01 mode is effectively suppressed and the TE11 mode successfully stimulated. A dual-resonant reflector is incorporated in the RBWO to effectively reflect the TE11 mode. An isotropic absorber is deployed in front of the dual-resonant reflector to reduce the external Q factor of the TM01 mode and avoid undesired modulation. These distinctive features of the RBWO, allow a circularly polarized TE11 mode output to be obtained. Particle-in-cell simulations show that for a beam voltage of 1.12 MeV and a beam current of 12.3 kA, circularly polarized TE11 mode microwaves with power 3.9 GW and frequency 6.4 GHz can be obtained.