Theory research of the longitudinal metal-loaded helical slow-wave RF characteristics

Considering azimuthal symmetrical harmonics and higher order harmonics in non-vane area, using field matching method and boundary condition of the ridge-loaded ring-plane slow wave structure, the dispersion equation of vane-loaded helical slow-wave structure is obtained, and coupling impedance and attenuation constant is deduced on the basis of the dispersion equation. The numerical simulation by MAFIA is compared with the theoretical calculation and experiment. They have consistent curve trend, which may explain the physics essence of the slow wave structure. The effect of the dispersion is discussed for different vane angles. The method provides a means for other types of vane-load helical slow-wave structures.