真空下激光烧蚀碳化钨铜多组分等离子体发射光谱的时空演化研究  

Study on the Temporal and Spatial Evolution of Optical Emission From the Laser Induced Multi-Component Plasma of Tungsten Carbide Copper Alloy in Vacuum

作　　者：袁舒 吴鼎[1] 武华策 刘佳敏 吕燕 海然[1] 李聪[1] 冯春雷 丁洪斌[1] YUAN Shu;WU Ding;WU Hua-ce;LIU Jia-min;L Yan;HAI Ran;LI Cong;FENG Chun-lei;DING Hong-bin(School of Physics,Dalian University of Technology,Dalian 116024,China)

机构地区：[1]大连理工大学物理学院,辽宁大连116024

出　　处：《光谱学与光谱分析》2023年第5期1394-1400,共7页Spectroscopy and Spectral Analysis

基　　金：国家自然科学基金青年科学基金项目(12005034);国家重点研发计划专项基金项目(2017YEE0301304)资助。

摘　　要：激光诱导击穿光谱技术目前已用于国内大科学装置EAST托卡马克壁诊断。在真空环境下,如何提升LIBS定量分析准确性是其进一步发展的瓶颈问题之一。在真空中,激光诱导等离子体具有高度时空非均匀性,对等离子体时空演化行为的研究,理解各个物种的演化规律,是进一步改进LIBS定量分析准确性的重要内容。针对托卡马克第一壁和偏滤器的材料相关的不同元素,该工作在真空环境下利用波长为1 064 nm、脉宽5 ns、功率密度6.3 GW·cm-2的脉冲激光对三元合金-碳化钨铜((WC)70Cu30)进行烧蚀产生多组分等离子体,使用线性阵列光纤实现了对发射光谱的时空分辨测量。以三种元素CⅠ833.51 nm, CⅡ657.81 nm, CuⅠ515.32 nm, CuⅡ512.45 nm, WⅠ429.46 nm, WⅡ434.81 nm六条谱线为研究对象,研究了激光烧蚀等离子体不同辐射机制的时间尺度以及多组分等离子体在扩张过程中发生的元素“空间分离”现象和“离子加速”现象。根据连续背景和六条谱线的时间演化规律,观察到连续辐射主要发生在等离子体膨胀早期80 ns内,离子谱线在30~300 ns,原子谱线在100~1 000 ns。空间分辨实验研究发现,C、 Cu、 W元素对应原子及离子的空间分布均有所不同,即真空中激光烧蚀多组分等离子体在扩张过程中发生了元素“空间分离”现象。将六条谱线的峰值位置和时间进行线性拟合,获得了对应物种的扩张速度,其速度范围在4.2~34.9 km·s^(-1)。结果表明,相对原子质量越小,对应粒子的速度越快(CⅠ>CuⅠ>WⅠ, CⅡ>CuⅡ>WⅡ);对应元素的离子速度大于其原子速度(CⅡ>CⅠ,CuⅡ>CuⅠ,WⅡ>WⅠ)。利用元素“质量分离效应”和“瞬态鞘层加速”的物理机制,对激光等离子体元素“空间分离”以及“离子加速”现象进行了讨论和解释。该研究结果为LIBS理论模型建立提供了重要的实验数据参考,也为提高真空LIBS定量分析准确性�The Laser-induced breakdown spectroscopy technique has been used for the wall diagnosis in EAST Tokamak.Improving the accuracy of LIBS analysis in a vacuumis one of the bottlenecks for further development and application.In a vacuum,laser-induced plasma evolution highly depends on time and space.Studying the spatial-temporal evolution of plasma and understanding the species’behavior is necessary to improve the LIBS accuracy further.Considering different elements related to the first wall and diverter used in Tokamak,the sample of ternary alloy-tungsten carbide copper((WC)70 Cu 30)was used in this work.Multi-component plasma was produced by nanosecond laser ablation in a vacuum with a wavelength of 1064 nm,the pulse width of 5 ns,and power density of 6.3 GW·cm-2.The temporal and spatial resolution measurement has been achieved using a linear fibre bundle.Six lines of CⅠ833.51 nm,CⅡ657.81 nm,CuⅠ515.32 nm,CuⅡ512.45 nm,WⅠ429.46 nm and WⅡ434.81 nm were selected to analyze the emission time scales.Moreover,the element separation in space and ion acceleration phenomena were also investigated.According to the spectrally-resolved time evolution results,it was found that continuous radiation mainly occurs in the early time of 80 ns,ionic emissions are 30~300 ns,and atomic emissions are 100~1000 ns.The spatial distribution of atoms and ions corresponding to C,Cu and W elements are all different,indicating the separated species occurs during multi-component plasma expansion.The peak position and time for the six lines have been linearly fitted to obtain the corresponding species velocity,which ranges from 4.2 to 34.9 km·s^(-1).The results also show that the smaller the relative atomic mass,the faster the corresponding expansion velocity.(CⅠ>CuⅠ>WⅠ,CⅡ>CuⅡ>WⅡ);the ion velocity is greater than its atomic velocity(CⅡ>CⅠ,CuⅡ>CuⅠ,WⅡ>WⅠ).The element separation in space and ion acceleration is attributed to the element mass separation effect and transient sheath acceleration,which also reveals

关 键 词：激光诱导击穿光谱 碳化钨铜 多组分等离子体 时空演化 质量分离效应 离子加速 

分 类 号：O433.4[机械工程—光学工程]