电极间距对空腔阴极自脉冲放电影响的机制

Influential Mechanism of Electrode Spacing on the Self-pulsing Discharge in Cavity Cathode Discharge

为了进一步揭示空腔阴极自脉冲放电特性和机理,利用槽型空腔放电结构实验研究了阴极和阳极间距对自脉冲放电特性的影响。同时利用流体模型模拟研究了空腔阴极放电击穿阶段的微观动力学过程。结果表明,自脉冲放电过程中存在明显的负微分电阻现象,自脉冲频率随着平均电流的增加近似线性增加。阴极和阳极间距对自脉冲放电特性有一定影响。随着阴极和阳极间距的增加,极间平均电压和自脉冲频率增高,电流峰值减小,自脉冲电压峰值和最低值增高,自脉冲上升沿时间增长。电流最低值基本不随极间距的变化而变化。模拟结果表明,自脉冲放电为由位于孔口位置处的低电流、低电子密度、轴向电场为主放电模式,向孔内放电为主、较高电子密度、径向电场为主放电模式的周期性转换过程。空腔阴极自脉冲放电为净正空间电荷层或者说是虚拟阳极由孔外向孔内再移到孔外,强度先增强后减弱再增强的一个反复过程。阴极和阳极间距越小,阳极对腔内放电影响越明显,腔内放电更强烈,电流峰值越高。另外,研究结果表明,放电单元的等效电阻值主要由放电空间电子密度决定:电子密度越高,等效电阻越低。

In order to further reveal the characteristics and mechanism of the self-pulsing discharge in cavity cathode discharge,the effect of electrode spacing on the characteristics of cavity self-pulsing discharge is studied experimentally by using the groove cavity electrode structure.At the same time,the fluid model is used to simulate the microscopic dynamics of the cavity discharge breakdown phase.The results show that there is an obvious negative differential resistance phenomenon in the process of self-pulse discharge,and the self-pulsing frequency increases approximately linearly with the increase of average discharge current.The distance between cathode and anode has an effect on the characteristics of self pulsing discharge.With the increase of the gap between cathode and anode,the average sustained voltage and the self-pulsing frequency increase,the peak value current drops,the maximum and the minimum values of self-pulsing voltage increase,and the rising time of self-pulsing increases.The current minimum value does not change with the change of electrode spacing.The simulation results show that the self-pulsing discharge is a periodic conversion process from the discharge mode with low current,low electron density and axial electric field at the orifice of cavity to the discharge mode with high electron density and radial electric field in the cavity.The self-pulsing of cavity cathode discharge can be regarded as a repeated process of net positive space charge layer or virtual anode moving from the orifice to the cavity and then to the orifice of the hole,and the intensity of net positive charge layer first increases,then decreases and then increases.The smaller the gap between cathode and anode is,the more obvious the influence of anode on the cavity discharge will be,the more intense the cavity discharge will be,and the higher the current peak will be.In addition,the results show that the equivalent resistance of the discharge cell is mainly determined by the spatial electron density.The higher the electron density is,the lower the equivalent resistance will be.