Study on G-band traveling wave tube based on piece-wise sine waveguide and sheet electron beam

In this paper, a novel G-band high-power sheet electron beam traveling wave tube (TWT) is designed by integrating piece-wise sine waveguide and sheet electron beam. First, a sheet-beam electron-optical system is developed, combining a piece-wise transverse-interleaving open-periodic-permanent-magnet (STI-OPPM) system and a high-compression-ratio elliptical Pierce electron gun. The STI-OPPM system achieves a peak magnetization of 1.03 T, while the electron gun emits a 23 kV, 230 mA sheet electron beam with an area compression ratio of 18:1. Under the focus of this magnetic system, the sheet electron beam, which has a transverse to longitudinal ratio of 6:1, can be 100% transmitted at the distance of 100 mm. Meanwhile, based on this electron-optic system, a piece-wise-sine waveguide slow wave structure (SWS) of TWT is proposed. The analysis of SWS indicates that it has an operating bandwidth of 50 GHz and a coupling impedance of approximately 1.6 Ω near the center frequency. Furthermore, a new high-frequency system is designed by using the characteristics of the new slow wave structure combined with phase velocity tapering and broadband energy coupling structure. The simulation results of beam-wave interaction show that the device can produce more than 300 W power output in the frequency range from 190 GHz to 201 GHz under the condition of electron beam voltage of 23 kV and electron beam current of 230 mA. The maximum power output at 195 GHz is 410 W and the corresponding gain is 36.2 dB.