激光诱导Ti等离子体电子温度的实验研究

室温,常压下,利用Nd∶YAG脉冲激光器产生的波长为1 064nm,脉宽12ns,能量分别180,230和280mJ的脉冲激光冲击Ti靶,使用中阶梯光栅光谱仪检测了三种激光能量下对应的光谱。调节延时器DG645的延迟时间,检测了延迟0~500ns时间范围内Ti等离子体对应激光能量下的发射光谱,分析光谱,可以得到了九条不同的的TiⅠ和TiⅡ等离子体谱线,证明在该实验条件下,Ti靶能够充分吸收能量电离且离子谱线具有不同的演化速率,利用Saha-Boltzmann法计算并分析Ti等离子体电子温度,实验结果表明:相同的延迟时间,激光能量越大,谱线相对强度越大,电子温度越高,谱线相对强度的变化量随激光能量的变化量增大而增大;在延时0~150ns内,三种激光能量下的等离子体电子温度和谱线的相对强度都随延迟时间的增加而快速下降,其中280mJ激光能量下的等离子体电子温度和谱线强度下降速率较快;在150~250ns范围内,电子温度和谱线强度均随延迟时间的增加有一个缓慢的上升,180mJ激光能量下的等离子体电子温度和谱线强度的上升速率较快。250~500ns范围内,三种激光能量下的电子温度和谱线强度均随延迟时间的增加而缓慢下降。

Experimental Investigation on the Electron Temperature of Laser-Induced Ti Plasmas

Laser pulse which was produced by Nd:YAG pulse laser ,with a wavelength of 1064 nm and pulse width of 12 ns , was used to shock the Ti target under the condition of room temperature and atmospheric pressure .By changing the laser energy (180 ,230 and 280 mJ) and adjusting the delay time through a digital delay generator of DG645 ,a series of plasma characteristic spectral lines of Ti alloy were obtained by a mechelle grating spectrometer in the time range of 0~500 ns .By analyzing the spec-trum ,9 different TiⅠ and TiⅡ plasma lines can be found .It was shown that under the experimental conditions ,the Ti target can fully absorb the energy to ionization and the ion spectral line has different evolution rate .The Saha-Boltzmann method was used to calculate and analyze the electron temperature of Ti plasma .The experimental results showed that at the same delay time ,the greater of laser energy was used ,the stronger of relative intensity of the line was obtained ,and the higher of electron temperature could be induced .When the variable quantity of laser energy increased ,the variable quantity of spectral line relative intensity will increase .In the delay time of 0~150 ns ,the plasma electron temperature and the spectrum line relative intensity of the three kinds of laser energy decrease rapidly with the increase of the delay time ,of which the electron temperature and spec-trum line intensity decrease faster under laser energy of 280 mJ .During 150 to 250 ns ,the electron temperature and spectrum line intensity have a slow rise with the increase of delay time ,and the rising rate of the plasma electron temperature and the spec-tral line intensity were faster when laser energy is 180 mJ .In the range of 250 to 500 ns ,the electron temperature and the spec-trum line intensity of the three kinds of laser energy decrease slowly with the increase of the delay time .