基于阴影法的脉冲CO_2激光Sn等离子体羽辉膨胀特性研究  

Research on Pulsed CO_2 Laser Produced Sn Plasma Plume Expansion Properties by Shadowgraph Technique

作　　者：吴涛[1] 王新兵[2] 王世芳[3] 谭荣[1] 

机构地区：[1]武汉工程大学理学院,湖北武汉430074 [2]华中科技大学武汉光电国家实验室,湖北武汉430074 [3]湖北第二师范学院物理与电子信息学院,湖北武汉430205

出　　处：《中国激光》2013年第1期36-40,共5页Chinese Journal of Lasers

基　　金：油气藏地质及开发工程国家重点实验室开放基金(PLN1205);国家自然科学基金(61078024)及国家自然科学基金(11104211)资助课题

摘　　要：基于阴影法测量了脉冲CO2激光Sn等离子体羽辉在缓冲气体中的膨胀特性,得到了羽辉边界位置及其等离子体碎屑动能随延时的变化规律,并利用修正的阻力扩散模型拟合了实验数据。研究表明,在入射激光脉冲能量为400mJ,脉冲半峰全宽为75ns,缓冲空气气压为1000Pa时,初期(延时小于100ns)Sn等离子体羽辉边界的膨胀速度可以达到3cm/μs,随着延时的增加,由于背景气体分子的热碰撞阻力作用,羽辉粒子的速度急剧下降,后期(延时大于800ns)羽辉碎屑离子膨胀速度降到了0.3cm/μs。修正的阻力扩散模型拟合的结果表明等离子体羽辉膨胀的极限尺寸xst=15.2mm,实验测试结果表明,羽辉碎屑粒子运动的极限距离约为16mm,理论模型与实验结果吻合较好。The characteristics of pulsed CO2 laser produced Sn plasma plume expansion under ambient air pressures are studied by shadowgraph technique.The dependences of Sn plume expansion position and plasma debris energy on delay time are obtained.The modified drag diffusion model is employed to fit the experimental data.Plasmas are generated by irradiating planar Sn targets using 400 mJ,75 ns pulses from a CO2 laser.Our results show that the estimated expansion velocity of the plasma in the early stage（delay time is less than 100 ns） is almost 3 cm/μs,and decreases rapidly with delay time to about 0.3 cm/μs at later stage（delay time is larger than 800 ns） because of the thermalization collisions with buffer gas pressure of 1000 Pa.Fitting results of modified drag diffusion model indicate that the plasma plume maximum size is xst=15.2 mm,which is found to agree fairly well with the measured data of 16 mm.

关 键 词：激光光学 激光等离子体 羽辉膨胀 阴影法 缓冲气体 

分 类 号：O53[理学—等离子体物理]