同轴谐振器低气压放电击穿瞬态电学行为研究

Study on transient electrical behavior for low-pressure discharge of coaxial resonator

气体微波电离引起的低气压放电效应是限制微波部件功率容量的可靠性问题之一,而击穿瞬态电学行为的研究有助于诊断系统响应。目前大功率微波部件的击穿诊断与电路系统联系不够紧密,而探究放电所产生的等离子体对系统的影响能够改善这一现状。以TEM模式下谐振频率为2.6 GHz的同轴谐振器为研究对象开展低气压放电实验,获得了100~1000 Pa气压范围内谐振器的击穿功率阈值随气压的变化关系实验曲线,并通过正反向调零模块中功率计记录气体电离击穿前后的S 11值。结合谐振器内部放电后的烧蚀痕迹将气体电离击穿后所产生的等离子体等效为圆柱型介质块,进行建模仿真获取放电发生后S 11与谐振频率随气压变化的关系曲线,分析并发现局部阻抗的负载状态随着气压的升高是逐渐由容性向感性转变。最后基于测试系统的调零模块计算得到电离击穿前后谐振器局部阻抗的变化量与气压的实验关系曲线,验证了建模仿真结果。

The low-pressure discharge effect caused by gas microwave ionization is one of the reliability problems that limit the power capacity of microwave components.The study on the electrical behavior of breakdown transients is helpful in diagnosing system response.Nowadays,the breakdown diagnosis of high-power microwave components is not closely related to the circuit system and exploring the effect of plasma generated by discharge to the system can improve this situation.The low-pressure discharge experiment was carried out with a coaxial resonator at 2.6 GHz in TEM mode,whose curve of the breakdown power threshold of the resonator in the range of 100~1000 Pa was obtained as a function of change with air pressure.The S 11 value before and after gas ionization breakdown was recorded by the power meter in the nulling system.Considering the ablation trace after the internal discharge of the resonator,the plasma generated after the ionization breakdown of the gas can be equivalent to a cylindrical dielectric block in this model.The relationship curve between S 11 and the resonant frequency with the change of air pressure after the discharge is obtained by simulation.We found that the load state of the local impedance gradually changes from capacitance to inductance with the increase of air pressure.Finally,based on the nulling module of the test system,the experimental relationship curve between the local impedance of the resonator before and after ionization breakdown and the air pressure is obtained,of which results are verified.