Efficient Time-Domain Simulations of a Helix Traveling-Wave Tube

An efficient time-domain discrete model of the interaction of an electron beam with an electromagnetic wave propagating in a slow-wave structure has been described by Kuznetsov. Using a projection of Maxwell's equations onto the eigenmodes of the structure, the evolution of the entire electromagnetic field can be reduced to the evolution of its amplitude alone in each period of the waveguide. The number of degrees of freedom of the system is thus greatly reduced. This model has been successfully applied in the case of coupled-cavity traveling-wave tubes (TWTs) and can be applied to klystrons, where the circuit field is localized between the gaps of the cavities. In this paper, we present the results of numerical simulations performed by applying this model to a helix TWT. We show that the results obtained are in very good agreement with theory. We also compare our results with those from frequency-domain TWT simulation software.