Prediction of Multipactor Breakdown Thresholds in Coaxial Transmission Lines for Traveling, Standing, and Mixed Waves

In this paper, we present a numerical model for predicting the multipactor breakdown effect in coaxial transmission lines. To validate this method, we have first compared our results with numerical data from other theoretical studies and with experimental measurements. Then, we have investigated the multipactor phenomena in coaxial lines considering three kinds of RF signals: traveling, standing, and mixed waves. From this paper, we conclude that different breakdown thresholds are obtained for any of the considered RF excitations under high values of frequency x gap product. This effect is attributed to the existence of regions with zero (or very low levels) electric field amplitude in the propagation direction, where electrons are absorbed before the discharge occurs.