半球空腔约束对激光诱导玻璃等离子体辐射增强特性的研究

Effects of Hemispherical Confinement on the Enhancement of Laser-induced Glass Plasma Radiation

为了增强激光诱导玻璃等离子体的辐射光谱信号,采用直径为10mm的玻璃纤维材质半球空腔对等离子体进行束缚,对比研究了无约束和约束两种实验条件下的辐射光谱信号.由于激光的聚焦情况对玻璃等离子体特性有较大影响,实验首先对激光在样品中的聚焦位置进行了优化,结果表明当样品表面位于透镜焦平面以上3mm处时激光诱导玻璃等离子体辐射光谱最强.然后采用时间分辨光谱对比研究了无约束和半球空腔约束下光谱强度的时间演变规律,并分析了谱线强度增大倍数的时间演变,结果表明在等离子体产生后6~15μs的时间内,半球空腔约束下谱线强度呈现出增强的现象,且具有不同能级的谱线增强程度不同,当采集延时为10μs时具有最优增强效果.最后研究了激光能量对半球空腔约束下等离子体辐射增强效果的影响,研究结果表明,随着激光能量增大,谱线增强倍数逐渐增加,当激光能量超过170mJ以后,谱线增强效果开始下降.

In order to enhance the radiation spectrum signal of laser-induced glass plasma, a hemispherical cavity which was made of glass fiber with a diameter of 10 mm was used to confine the plasma. The spectrum signals with confinement and without confinement were compared. Since the focusing of the laser has a great influence on the properties of the glass plasma, the focusing position of the laser in the sample was first optimized. The results show that when the sample surface is 3 mm above the focal plane of the lens, the spectral singnal from the laser-induced glass plasma was the strongest. Then the temporal evolution of spectral intensity under unconstrained and spatially constrained by a hemispherical cavity with the inner diameter of 10 mm was studied. The time evolution of the enhancement factor og the spectral intensity was analyzed. The results show that the spectral lines with confiment presents an enhanced phenomenon in the period of 6~ 15 μs after plasma generation. And the degree of enhancement of spectral lines with different energy levels is different. The maximum enhancement is achieved when the acquisition delay is 10 μs. Finally, the effect of laser energy on the enhancement of plasma radiation was studied. The results show that with the increase of laser energy, the enhancement factor of the spectral line is gradually increased. When the laser energy exceeds 170 mJ, the spectral enhancement effect begins to decrease.