An Accurate Analytic Model for Traveling Wave Tube Dispersion Relation

Abstract -- We construct an analytical model for the dispersion of the hot modes in a traveling wave tube (TWT) based on the Lagrangian field theory, upgrading its constants to be frequency-dependent. The frequency dependence of the parameters of the TWT slow wave structure (SWS) is recovered from full-wave simulations by standard software (e.g., CST). We applied the model to study the hot modes of a helical-based TWT and found an excellent agreement between the results from our model and those from particle in cell (PIC) simulations. Our additional studies show that the proposed approach can be applied to various SWS geometries.