Experimental Study on Breakdown Characteristics of Microwave Gas Discharge Tubes

Microwave gas discharge tubes (GDTs) obtain energy from microwaves to generate an ionized plasma to reflect microwaves. In order to study and analyze the breakdown characteristics of microwave GDTs, including the time-domain characteristics and power loss characteristics, a broadband microwave GDT sample in
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-band with an ignitor was prepared and a breakdown experimental platform with an operation frequency 2.458 GHz was designed and constructed. The experiment was carried out without changing the structure of the tube and the gas composition inside the tube. The ignition voltage pulse was synchronized with the input microwave pulse, so that the tube broke down at a time point in the second half of the microwave pulse. A broadband oscilloscope was used to collect the time-domain waveform data of the leakage and reflection signals before and after the breakdown, respectively. The data were statistically analyzed to focus on the breakdown time point and the change law of the breakdown waveform. The results indicate that the tube discharge process which broke down at a time point within a pulse is different from that under a whole pulse, and there is a prebreakdown process. The time required for the prebreakdown and the time point of breakdown of the tube are discrete and are related to the input power and the ignition voltage. The arc loss decreases slightly with increasing input power. When the tube structure and gas composition are fixed, the input microwave power and ignition voltage can be adjusted to enhance the stability of the tube and reduce the loss to improve the reflection efficiency.