Analytic theory of relativistic high power microwave generator with coaxial slow wave structure

In this paper, a linear theory is presented of a relativistic high power microwave generator with coaxial slow wave structure. The space-charge-limiting current of a coaxial cylindrical waveguide is derived, which is larger than that of a hollow cylindrical waveguide. Thus, the electron beam in the former has more kinetic energy than that in the latter when the cathode potential and the current are the same and the coaxial device might obtain higher beam-wave conversion efficiency. Also derived is the dispersion relation for a coaxial cylindrical waveguide with sinusoidally varying wall radii. For the case of dispersion relation without considering the beam space charge effect, the theoretical results agree very well with the simulation results with Superfish. According to the numerical so