Traveling-Wave Tube Harmonic Amplifier in Terahertz and Experimental Demonstration

In this paper, a novel traveling-wave tube (TWT) harmonic terahertz (THz) amplifier is proposed for a high-power, wideband, and practical electromagnetic vacuum radiation source. The amplifier is based on the reuse of harmonic information in the spent beam of a normal TWT by harmonic generation, selection, amplification, and coupling. In order to verify this concept, a W-band folded waveguide pulsed TWT with a second-harmonic extraction system in Cascade has been developed for a G-band (170-260 GHz) TWT second-harmonic amplifier. Simulation results from CST Particle Studio show that the amplifier exhibits a good performance. Then, a prototype of the amplifier was fabricated and tested. The experimental results show that over 100-mW second-harmonic output power at most frequencies of the 11.4 GHz of bandwidth at 1% duty cycle was achieved, and the maximum second-harmonic output power reached 500 mW. This paper demonstrates the feasibility that TWT harmonic amplifiers can be used as a potential THz vacuum radiation source, and further progress in development of such novel THz devices is anticipated.