FDTD investigation of cylindrical waveguides with azimuthal corrugations excited by axisymmetric TE modes

In this work we investigated the scattering parameters and mode conversion of axisymmetric TE modes in smooth cylindrical waveguides with wedge-shaped azimuthal corrugations. In particular, we studied the effect of the length of the corrugated region on the scattering parameters and on the mode conversion. The field distribution was derived by the FDTD code COCHLEA and further post-processed using the COPP code. Results showed that the incident mode is converted to an ensemble of modes, the azimuthal indices of which are given by the SHM criterion. Azimuthal corrugated waveguides are usually employed in the gyrotron beam-tunnel to enhance the suppression of the parasitic modes.