The effect of the position of the slow-wave structure relative to the cutoff neck on the resonance properties of the electrodynamic system of the relativistic Backward-Wave oscillator

A numerical model based on the incomplete Galerkin method is used to calculate frequency characteristics of electrodynamic systems containing a cathode cutoff neck and a section of a corrugated waveguide placed at an arbitrary distance A from it. These electrodynamic systems, which are widely used in experimental relativistic backward-wave oscillators (BWOs), are shown to exhibit their own resonance properties. These properties strongly depend on Δ and are significantly different from the resonance properties of the corrugated waveguides that they contain. Resonance frequencies and Q-factors of these systems are found to change quasi-periodically when A is varied by about a half-wavelength of the E 01 mode. A classification for the BWO resonances and distances A is introduced. The effect of resonance properties of the studied electrodynamic systems on the starting characteristics of the relativistic BWOs is discussed.