Analysis of dielectric rods with arbitrary shape for low-dispersion slow-wave structures in helix TWTs

The introduction of rods with optimized cross-sectional shape in slow-wave structures (SWSs) for wideband helix traveling-wave tubes can sensibly improve the dispersion maintaining an adequate interaction-impedance level. In this brief, a procedure for analyzing helix SWSs loaded with rods of arbitrary shape, by using an analysis method adopting the inhomogeneous dielectric loading approach, is proposed. The advantages, in terms of SWS-dispersion improvement, of adopting optimized rod shapes in comparison to the typical rod shapes (i.e., rectangular, circular, and T-shaped) utilized up to now, are also demonstrated.