Investigation of a Broadband High-Power Incline Flat-Roofed Sine Waveguide for G-Band Sheet Beam TWT Amplifier

In this article, a novel incline flat-roofed sine waveguide (IFRSWG) was proposed for high-power broadband G-band traveling-wave tube (TWT). The novel slow wave structure (SWS) exhibits a 48% higher interaction impedance than the conventional modified flat-roofed sine waveguide (MFRSWG) while maintaining comparable dispersion characteristics. Three-dimensional PIC simulation results demonstrate that the maximum output power, electron efficiency, and −3-dB power bandwidth of two-section IFRSWG TWT reach 462 W, 8.09%, and 54 GHz, respectively. These results represent a 27% higher maximum output power and electron efficiency, a 50% broader −3-dB bandwidth, and more than 60% lower saturated input power against MFRSWG. Additionally, a sheet beam (SB) electro-optical system, which includes an SB gun and a uniform magnetic (UFM) focusing system, has been designed to complement the high-frequency system. Simulation results indicate that an SB with a voltage of 23.8 kV and a current of 240 mA can transport over 41 mm without interception in the beam tunnel under a peak magnetic field of 1.2 T. Finally, the UFM focusing system has been fabricated and experimentally verified, demonstrating the feasibility of achieving beam focusing with high current density. These results indicate that IFRSWG SWS has significant potential for high-power broadband THz SB TWT applications.