Design of a Multistage Depressed Collector for ${W}$ -Band Pulsed Traveling-Wave Tubes

This article presents a design method for multistage depressed collectors (MDCs) in W-band traveling -wave tubes (TWTs) using microwave tube simulation studio (MTSS) code. First, the conditions of the spent electron beam, including electron position and velocity distributions, were simulated. Then, to verify the feasibility and effectiveness of the simulation, the output power, electronic efficiency, collector efficiency and overall efficiency of the existing 250-W W-band pulsed TWT with a single-stage collector were also simulated making use of the above-spent beam conditions at the entrance of the collector. The simulated data were compared with the test results, indicating a reasonable agreement between them. Finally, the spent beam conditions at the entrance of the collector were employed to design a four-stage depressed collector, based on the folded waveguide circuit of the TWT. The simulated results showed that the overall efficiency of the TWT with the designed four-stage depressed collector increased by more than 37.26% in the whole frequency band, with the maximum overall efficiency of 44.65%. In comparison with the single-stage depressed collector, the collector efficiency and the overall efficiency of the TWT were increased from 75% to 88.85% and 26.45% to 44.65%, respectively. This article is believed to provide some guidance for the design of MDC of higher frequency band TWTs.