Thermal and stress analysis of the sine waveguide slow-wave structure traveling wave tube with operating 95 GHz

Traveling-wave tube (TWT) is the most widely used vacuum electronic power amplifier because of its broadband, high power and high efficiency. When the TWT is working normally, the slow-wave structure (SWS) acts as a place for the interaction between the electron beam and electromagnetic wave. Especially for TWTs operating in the millimeter wave and terahertz bands, the conductivity loss is a problem that cannot be ignored. Due to the conductivity loss of the SWS, the TWT generates a large amount of heat while generating high power. Therefore, it is particularly important to conduct thermal analysis and thermal stress analysis on the TWT before the actual tube fabrication. In this paper, a broadband high-power TWT is designed for the SWS based on the all-metal sine waveguide (SWG) with better heat dissipation and excellent transmission properties. At the typical frequency point of 95 GHz within the operating bandwidth, the output power is 200.97 W, and the heat loss power is about 36.7 W. Thermal analysis and thermal stress evaluation of the TWT structure are carried out using ANSYS Workbench. We evenly distribute the power loss to the slow-wave circuit to obtain the temperature distribution. The maximum temperature at the end of the slow-wave circuit is 197 °C when the TWT is under continuous wave operating conditions and the output power is about 200 W. This value is far lower than the melting point of high-conductivity oxygen-free copper (HCOFC), which can meet the design requirements of TWTs. The calculated results of the stress distribution show that the maximum value is 20 Mpa. The research work in this paper has certain guiding significance for the quality reliability of TWT in engineering application.