不同电极结构下微间隙空气放电及击穿机制

Micro-gap Air Discharge and Breakdown Mechanism Under Different Electrode Structures

为了研究低电压、微间隙中不同电极结构对放电微观特性的影响,采用粒子法(PIC/MCC)进行仿真,着重研究了不同电极结构(球形、柱形、锥形)下击穿放电的起始和发展过程,通过对电极间距为微米级的仿真研究,并与Paschen曲线进行对比分析发现:在电极间距为1~4μm范围内的放电属于场致发射机制。分析了电极结构对空间电场分布、粒子数密度、电流强度和放电通道的影响,结果发现:锥形电极和球形电极在微间隙内电场分布局部不均匀,在阴极表面更容易形成场致发射现象从而对击穿电压阈值产生影响,同时,电极结构对电场分布的影响最终影响阴极表面场致发射强度和等离子体通道形成的有效面积,影响场致发射电流大小以及放电通道形成的快慢。经实验进一步验证了电极结构对击穿电压和放电时间的影响:相同情况下,锥形电极的击穿电压最小且相对于球形电极和柱形电极最先击穿,放电时间最短;柱形电极的击穿电压最大且放电时间最长。

In order to study the influences of different electrode structures in low voltage and micro-gap on the discharge micro-characteristics,the particle method(PIC/MCC)is adopted for simulation,and the study of the breakdown discharge under different electrode structures(spherical,cylindrical,and conical)is focused on.In the initial and development processes,through the simulation study of the micron-level electrode spacing,and a comparative analysis with the Paschen curve,it is found that the discharge within the range of 1~4μm between the electrodes belongs to the field emission mechanism.The influences of the electrode structure on the spatial electric field distribution,particle density,current intensity and discharge channel are analyzed.It is found that the electric field distribution of the tapered electrode and the spherical electrode is locally uneven in the micro gap,and it is easier to form a field emission phenomenon on the surface of the cathode,which impairs the breakdown voltage threshold.At the same time,the influence of the electrode structure on the electric field distribution ultimately affects the field emission intensity of the cathode surface and the effective area formed by the plasma channel,and affects the size of the field emission current and the speed of the discharge channel formation.Experiments have further verified the influences of the electrode structure on the breakdown voltage and discharge time:under the same circumstances,the taper electrode has the smallest breakdown voltage and is the first to break down relative to the spherical electrode and the cylindrical electrode,and the discharge time is the shortest.The breakdown voltage of the cylindrical electrode is the largest and the discharge time is the longest.