Development of a novel overmoded sub-terahertz inclined coaxial clinotron with asymmetric mode suppressed

Abstract

Overmoded coaxial high frequency structures can improve the power capacity of vacuum electron devices (VEDs) and make the fabrication and assembly of the devices easy in the terahertz band, but they also lead to mode competition and deleterious effect on the beam-wave interaction. The numerical investigation on the cold cavity characteristics indicates that the dispersion curve of the quasi-TEM mode almost overlaps with the dispersion curve of the high-order quasi-TE11 mode, and the 3-D numerical simulation results also illustrate that due to the mode competition, the quasi-TEM cannot be excited steadily in the VEDs with traditional coaxial SWSs with the available current density. In order to effectively suppress the mode competition of overmoded coaxial SWSs, novel inclined coaxial slow wave structures (SWSs) are proposed in this paper. As the overmoded ratio of the SWSs reaches 9.7, the 3D particle-in-cell simulation results indicate that this novel device can successfully produce the terahertz wave with the output power of 571 W at the operating frequency of 0.338 THz, and the frequency spectrum of the generated signal is very pure. The field distributions in the inclined coaxial SWSs illustrate that there is no asymmetric mode excited in the proposed device.