激光大气等离子体的空间分布特性

Spatial distributions of laser-induced air plasmas

利用Nd:YAG激光器产生的1.06μm激光束(脉冲能量为500 mJ,脉冲宽度为10 ns,重复频率为30 Hz)聚焦形成长约8 cm、直径5 cm的激光大气等离子体柱,分别沿激光束方向和垂直于激光束方向探测了该等离子体柱的空间分辨光谱,并由此反演得出电子密度和电子温度空间分布特性。实验结果表明:激光大气等离子体中各种离子和电子呈泪滴型分布,即沿激光束方向不对称,而垂直激光束方向对称分布,最大电子密度1018/cm3,最高电子温度3000 K。

The spatial distributions were explored in the laser-induced air plasmas for clearer understanding of the micro- mechanism. A column of plasmas were formed by focusing Nd：YAG laser beam at 1.06 μm （energy is about 500 mJ/pulse, pulse width 10 ns, and frequency 30 Hz ）. The column was about 8 cm long and 5 cm in diameter. The spectra of the column in different position have been detected from vertical and parallel direction of laser beam respectively. From these data, the electron densities and the electron temperature distributions in the laser-induced air plasmas can be estimated. The experimental results indicate that the laser-induced air plasma exists in the shape of a tear drop, symmetrical in the vertical direction but not symmetrical in the horizontal direction. The largest electron density is about 10^18/cm^3 and the highest electron temperature is about 3000 K.