Effect analysis of angular momentum on coaxial multipactor with 1D3V statistical modeling

Abstract

How does the multipactor threshold voltage vary when two semi-infinite parallel plates are bent into coaxial lines? This topic with respect to the geometric effect on multipactor formation is essential for the optimal design of multipactor-free microwave systems. It requires accurate multipactor threshold analysis of the coaxial lines with the consideration of electron angular momentum, which is not considered in most multipactor theoretical approaches for efficient threshold calculations. To address this effect from the perspective of multipactor threshold analysis, this work presents an improved implementation of the multipactor statistical modeling (1D3V modeling) by constructing the joint probability density function with angular emissions and impacts of secondary electrons included. On that basis, a multipactor susceptibility chart of coaxial lines is conducted and compared with the experimental results, and multipactor threshold voltage for varying ratios of outer to inner conductor radii (radius ratio) is calculated to quantitatively investigate the effect of electron angular momentum. The results indicate that the 1D3V modeling can achieve fairly good agreement with the experimental result and relatively better accuracy of threshold calculation at first multipactor orders with comparison to the 1D1V result which only regards the radial momentum. With different variations of the threshold voltage from the 1D1V result, the 1D3V result reaches its minimum at a specific radius ratio before the sudden rise, and the discrepancy becomes more significant for the high-order multipactor, revealing the indispensable effect of angular momentum on the coaxial multipactor. The intricacies of the mechanism analysis will be further explored in the paper.