An investigation of pulsed high power microwave dielectric surface flashover



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Breakdown events in high power microwave (HPM) systems have been a severely detrimental phenomenon and have inhibited the further development of HPM systems and technologies. The predictability of these events has proven difficult due to the presence of non-uniform microwave fields and the effects of specific gas species and pressures associated with various HPM applications. One particularly difficult aspect is the predictability of the appearance of initial electrons which initiate breakdown events. The source of these initial electrons is highly dependent upon the geometry and system in question. Once an electron appears in a breakdown region, the determination of the time to reach some critical electron density can also prove difficult due to the inherently statistical gaseous mechanisms involved with the avalanche event.

It is the purpose of the investigation presented in this paper to provide some insight towards predicting the initiation of HPM breakdown events which could lead to better system reliability. The focus of this investigation assumes the presence of a dielectric interface to separate the radiating side from the microwave generation side of an HPM system. The research simulates a high altitude, low pressure environment for HPM propagation. In the event of breakdown at the dielectric interface, the transmitted microwaves could be rapidly cut off by way of reflection or absorption into the generated plasma. Various theoretical and experimental aspects regarding this phenomenon are discussed as well as the development of a statistical model which predicts HPM surface flashover events for various experimental conditions.