EM Analysis of Vane-Loaded RF Interaction Structure for its Potential Application in Gyrotrons

All-metal RF interaction structures have potential to be used in high-power high-frequency gyro-devices. With this intension, the vane-loaded all-metal RF interaction structure has been field analyzed in this paper. Electromagnetic fields in various regions of the structure, boundary conditions, and finally dispersion relation for the structure have been derived starting from the basic principles. Dispersion relation has been solved using Powel-Dogleg method. Validation of the present analysis has been done for the special case of zero vane angle, and vane depth equal to outer radius of structure wall radius, which is identified as the dispersion relation of the TEon mode of a smooth wall cylindrical waveguide, that is, of an unloaded waveguide. Parametric analysis on dispersion characteristic revealed that numbers of vanes and angular width of the vanes are more sensitive than the radial depth of the vanes. It has been found that dispersion shaping using vane-loaded structure results in mode-rarefaction which may be advantageous for avoiding mode-competition in over-moded operation of gyrodevices.