Using Phase Jumping Method to Enhance the Beam–Wave Interaction Efficiency in Terahertz Folded-Waveguide Traveling-Wave Tube

The folded-waveguide (FWG) traveling-wave tube (TWT) is a promising high-power terahertz (THz) amplifier. However, it is challenging to develop THz FWG-TWT with high beam–wave interaction efficiency. In this work, a phase jumping technology, which originates from free-electron lasers, is proposed to boost the beam–wave interaction efficiency of THz FWG-TWT. A modified slow wave structure acts as the phase shifter to adjust the phase gap between electron beam and electromagnetic wave. By jumping the phase gap to an appropriate value, the bunching center of electron beam keeps for a long time in the deceleration region. Thus, more energy is transferred to electromagnetic wave from bunching electron beam. To verify such proposition, a THz FWG-TWT example utilizing the phase jumping is presented in this article. Compared with conventional one, its efficiency within the operation bandwidth from 212 to 224 GHz is improved by 60%–140%.