基于临界电子密度的多载波微放电全局阈值分析

多载波微放电即发生在宽带、大功率真空无源微波部件中的二次电子倍增放电现象, 是影响空间和加速器应用中无源微波部件长期可靠性的主要隐患. 多载波微放电全局阈值功率的预测对于工作在真空环境中的微波部件至关重要, 但迄今尚无有效方法进行上述阈值的准确分析. 本文将微放电发生过程中二次电子分布区域等效为等离子体, 通过在理论上建立微波部件的电磁特性和电子密度间的对应关系, 提出了一种基于测试系统可检测水平的多载波微放电全局阈值功率分析方法. 为了能够通过蒙特卡罗优化方法得到全局阈值, 进一步基于电子加速的类半正弦等效, 提出了微放电演化过程中电子数涨落的快速计算方法. 基于以上两种方法得到的针对实际微波部件的全局阈值分析结果与实验结果相符合. 不同于传统基于多载波信号功率分析的经验方法, 本文基于临界电子密度判断依据和电子数涨落快速计算, 为多载波微放电全局阈值的准确预测提供了一种高效的分析方法.

Global threshold analysis of multicarrier multipactor based on the critical density of electrons

Multicarrier multipactor, which is found in the wideband high power vacuum microwave passive components, potentially threatens the reliability of microwave systems in space and accelerator applications. The global threshold analysis of multicarrier multipactor is of vital importance for the risk assessment of high power vacuum devices. Till now, however, no effective solutions for the global threshold analysis of multicarrier multipactor have been proposed for practical microwave components with complex structures. In this paper, an efficient approach capable of evaluating the global threshold of multicarrier multipactor based on detectable level of multipactor test system is presented. Electromagnetic characteristics of the microwave device are theoretically related to the electron density by equivalently considering the distribution zone of electrons as a plasma medium. In order to obtain the global threshold using the optimization algorithm, such as the Monte Carlo method, we further propose an efficient approach capable of rapidly computing the fluctuation of number of electrons in the evolving process of a multicarrier multipactor based on the equivalency of half-sine-like segments for the acceleration of electrons. Analytical results comply with the tested thresholds. Different from the conventional equivalent power using the empirical rule, the proposed approach is based on the criterion of critical density of electrons and rapidly computing the fluctuation of number of electrons, providing an efficient method for the accurate global threshold analysis of multicarrier multipactor.