PIC Simulation and Preliminary Experiment on a G-band Sheet Beam Traveling-Wave Tube

A sheet beam traveling-wave tube (SBTWT) with the center frequency of 220 GHz is introduced, known for its advantages in high power, wide bandwidth, high gain, and high efficiency, and it is an indispensable component in high-power G-band amplifiers. The SBTWT is designed with a “ T “-shape staggered double-vane slow-wave structure (SWS), offering the technical benefits of low loss and wide bandwidth. It incorporates a centralized attenuator to enhance its gain capacity. To achieve high-power output, a large current density sheet beam electron gun using a scandate cathode is utilized as the free electron source. And a tunable periodic cusped magnetic (PCM) focusing system is employed to focus the sheet beam, ensuring its stable and long-distance transmission through SWS. This research also explores a depressed collector to recover the energy of “residual electrons”, thus improving the efficiency of the SBTWT. PIC simulation results indicate that at 220 GHz, the SBTWT can generate a saturated output power of 206 W, with a 3 dB bandwidth exceeding 50 GHz, and a gain over 31 dB. These components, such as the sheet beam electron gun, “T“-shape staggered double-vane SWS, tunable PCM focusing system, depressed collector, input and output couplers were fabricated and tested. Then, the SBTWT was assembled and the sheet beam transmission experiment was carried out. These research efforts pave the way for the application of sheet beam TWTs in pivotal fields such as deep space communication, radar detection, imaging, and high-speed data communication.