荧光法研究空气等离子体膨胀动力学过程

Study of the Air Plasma Expansion Dynamics by Fluorescence Method

基于等离子体荧光法研究了Nd∶YAG纳秒1 064nm激光脉冲诱导击穿空气等离子体的膨胀动力学过程,用ICCD相机捕获了不同激光脉冲能量诱导的空气等离子体随时间演化图像,给出激光能量100,150,200,300mJ时击穿空气产生的空气等离子体波阵面前沿的膨胀距离,推演出空气等离子体的扩展速度。实验结果表明等离子体发光区域主要分布在等离子体膨胀区域,等离子体荧光强度随时间增加变强然后渐渐变弱,膨胀区域逐渐增大,在300mJ,22ns膨胀距离最大达到3.76mm,等离子体扩展速度在膨胀初期达到105 m·s-1量级,在膨胀16ns内迅速衰减,随后趋于平缓。激光脉冲能量越大,引起空气击穿的时刻靠近高斯激光脉冲上升阶段。

The expansion dynamics of air plasma induced by 1 064 nm nanosecond laser pulse was studied by plasma fluorescence method.The time evolution images of air plasma expansion were acquired using the ICCD camera at different laser pulse energy,and the expansion velocity of air plasma was deduced based on the air plasma frontier expansion wave front distance at 150 mJ.The experimental results show that the plasma fluorescence was mainly distributed in the plasma expansion region,the plasma fluorescence intensity firstly increased then became weaker and the expansion area increased gradually with time evolution,.The biggest expansion distance was 3.76 mm with 300 mJ at 20 ns.The plasma expansion speed was the order of magnitude of 105m·s-1 at the early stage of expansion process.The expansion speed of air plasma decayed rapidly within 16 ns,then changed slowly with time.The time of air breakdown was close to the rising phase of laser pulse when the greater laser pulse energy was radiated.