An analysis of the sloped-ring slow-wave structure for high-power traveling-wave tubes

In this work, a sloped-ring (also called v-shape) helix slow-wave structure is analyzed in order to obtain its dispersion and interaction impedance characteristics. This slow- wave structure is a variant of the contra-wound one in the same way as the ring-bar. The fact is that the spatial distortion of the sloped-ring helix is smaller than the ring-bar one if the both are compared to the contra-wound one. A mathematical model was developed for predicting the dispersion and the interaction impedance characteristics. Plots of these two curves varying some constructing parameters are shown. Measurements of the normalized phase velocity are given for v-shape and ring-bar helices with and without dielectric loading. These results are compared to the mathematical model based on the contra-wound helix.