背景气体中激光Al等离子体演化的干涉诊断研究  

Interferometric diagnosis of laser-produced Al plasma evolution under different background gases and pressures

作　　者：吴梦婷 曹世权 苏茂根[1] WU Meng-ting;CAO Shi-quan;SU Mao-gen(Key Laboratory of Atomic and Molecular Physics and Functional Material of Gansu Province,College of Physics and Electronic Engineering,Northwest Normal University,Lanzhou 730070,Gansu,China)

机构地区：[1]西北师范大学物理与电子工程学院,甘肃省原子分子物理与功能材料重点实验,甘肃兰州730070

出　　处：《西北师范大学学报（自然科学版）》2024年第2期43-50,共8页Journal of Northwest Normal University(Natural Science)

基　　金：国家自然科学基金资助项目(12204382);甘肃省创新群体资助项目(20JR5RA541)。

摘　　要：利用自主搭建的马赫-曾德尔激光干涉诊断系统研究了空气压强在1 atm和0.1 atm以及氩气在1 atm下纳秒脉冲激光烧蚀产生Al等离子体的冲击波膨胀和电子密度演化.从测量的干涉图中提取了等离子体冲击波的膨胀轮廓,诊断了等离子体的电子密度.研究结果表明,在空气背景气压为0.1 atm时,等离子体冲击波轮廓和速度都较大;而压强在1 atm时,氩气环境中等离子体冲击波的膨胀速率和轮廓均较小.空气环境在0.1 atm下,冲击波的横向膨胀速度在50 ns时达到了约3.4 km·s^(-1),但随着延迟时间的增加快速衰减,5μs后,3种情况下的冲击波均接近声速.此外,空气环境0.1 atm下等离子体空间区域较大,整体电子密度较低;而氩气环境在1 atm下,等离子体空间区域较小,整体的电子密度较高,在300 ns时核心区域电子密度达到了10^(18) cm^(-3).结果进一步显示了背景气压对等离子体膨胀约束具有主导作用,而压强相同时,氩气环境对等离子体的约束要强于空气环境.The study of laser-produced plasma under different background gases and pressures is of great significance for optimizing the application of laser induced breakdown spectroscopy(LIBS).In this work,the shock wave expansion and electron density evolution of Al plasma produced by nanosecond pulsed laser ablation under 0.1atm,1 atm in air environment and 1 atm in argon environment were studied by using a self-built Mach-Zehnder laser interference diagnostic system.The expansion profile of shock wave is extracted and the electron density of plasma is diagnosed from the measured interferograms.The results show that in the air environment,when the background pressure is low(0.1 atm),the profile and velocity of the plasma shock wave are large,while when the pressure is consistent(1 atm),the profile and velocity of the shock wave in the argon environment are small.The horizontal expansion velocity of shock wave reaches about 3.4 km/s,1.9km/s and 1.3 km/s under 0.1 atm,1 atm in air and 1 atm in argon,respectively,and they decrease rapidly with increasing delay time,approaches the speed of sound after 5μs.In addition,the plasma space area is large and the overall electron density is low under 0.1 atm in air,while under 1 atm in argon,the plasma space area is small and the overall electron density is high,the electron density in the plasma core area reaches 10^(18) cm^(-3).The results further show that the background pressure plays a dominant role in the plasma expansion constraint.When the background pressure is consistent,the confinement of argon environment to plasma is stronger than that of air environment.The research results provide a reference for understanding the evolution behavior of laser-produced plasma under different background gases and pressures and optimizing LIBS technology in the related application.

关 键 词：激光等离子体 干涉诊断 冲击波 电子密度 

分 类 号：O53[理学—等离子体物理] TN249[理学—物理]