高压直流下激光触发空气间隙放电的实验研究

Experimental Study on Air Gap Discharge Triggered by Pulsed Laser Under HVDC Condition

随着激光诱导等离子体和空气放电应用结合的日益紧密,激光诱导放电的基本物理过程也得到了广泛的研究。围绕直流高压条件下的纳秒激光诱导放电,研究了不同实验条件(激光入射方式、激光焦点位置)对击穿延时和抖动的影响,并利用ICCD快速照相观察了等离子体的发展过程。结果表明:激光径向入射时,激光焦点偏电极侧有利于击穿延时和抖动的降低;相同激光能量条件下,间隙电压由35 kV提升至45 kV,平均击穿延时由108μs降为4.8μs;相对于径向入射,轴向入射激光烧蚀电极表面并发射电子,可诱导产生一条平直的放电等离子体通道,间隙的平均击穿延时达到亚μs量级(800 ns)。

Along with the application of combining the laser produced plasmas with gas discharge, the fundamental physics of laser triggered discharge are paid widely attention. In this work, the air breakdown triggered by the pulsed under the high voltage direct current（HVDC） condition were experimentally investigated. Special care was taken with the influences of the laser focus location as well as the laser incident mode on the occurrence probability of the gap breakdown. Plasmas evolution was visualized by the fast ICCD photography. Results revealed that the breakdown delay time and jitter would decrease pronouncedly when the laser focus location moved closer to the electrode surface from the gap middle. With the same incident laser energy, the average breakdown delay time decreased rapidly from 108 p.s to 4.8 kts when the gap voltage was increased from 35 kV to 45 kV. In the end, a linear discharge channel was also found when the incident laser was introduced in the axial direction, and an average breakdown delay time as low as 800 ns was achieved.