Traveling-wave tubes on looping waveguides with a potential jump

Using computer simulation, a study of the effect of a potential jump on the interaction processes in O-type traveling-wave tubes has been carried out. In these devices, the interaction of the electron beam with a slowed down electromagnetic wave is carried out. To slow down the electromagnetic wave, various electrodynamics systems are used: spiral, on chains of coupled resonators, etc. In this work, we have chosen a slowing down system in the form of a chain of looping rectangular waveguides. Its advantage is that it has a wide bandwidth and each link in such a chain is coordinated with the adjacent ones. To assess the effect of a potential jump on the interaction processes in O-type traveling-wave tubes, a mathematical model has been developed, which takes into account most fully all the factors influencing the interaction processes. These include: relativistic effects during the motion and interaction of electrons, sagging of fields in the gaps of the waveguide, losses in the walls of the waveguide, taking into account the space charge fields (taking into account the periodization of the fields). Based on the developed model, a program was compiled and calculations of various variants of TWT were carried out for accelerating voltages of 20–500 kV, electron beam currents of 0.3...160 A. When performing calculations, the gap with a potential jump was located in different places of the TWT slow-wave structure and its location was chosen where the maximum effect on the electron bunching processes is manifested. As the calculations have shown, the potential jump makes it possible to increase the output power of the TWT by 15–20 %. It can be noted for comparison that the use of a potential jump in multi-cavity klystrons [1] also leads to an increase in the output power by 15-25 %. This confirms the reliability of the mathematical models used in TWT and klystrons.