高真空环境下激光诱导击穿光谱技术对镍基合金的定量分析研究

激光诱导击穿光谱(LIBS)是一种极具潜力的托卡马克装置壁材料原位诊断技术,目前应用于全超导托卡马克核聚变实验装置(EAST)上,它能实时、原位、在线监测材料表面的成分变化。但在高真空条件下,LIBS技术对壁表面成分的准确定量分析还面临很大的挑战。实验模拟了EAST装置运行时的高真空环境,采用纳秒脉冲激光对5种标样(镍基合金)进行烧蚀产生等离子体并获取光谱。利用多元玻尔兹曼斜率法和斯塔克展宽法分别计算电子激发温度和电子密度;结合单点校正(OPC)法开展了定量研究,并与传统的无校准定标(CF-LIBS)结果进行了分析比较。结果显示相对于CF-LIBS法,OPC法对合金中的各元素定量准确度均有明显提高。对于基体元素Ni,相对误差小于3.92%;对于原子百分比为3.11%的Mo元素,相对误差由155.41%降到了34.32%。单点校正法为实现LIBS技术在线测量壁表面杂质沉积量提供了理论参考。

Quantitative analysis of the nickel base alloy by laser-induced breakdown spectroscopy in high vacuum environment

Laser-induced breakdown spectroscopy (LIBS) is a promising in-situ diagnosis technology for the wall materials in tokamak devices. Currently, it has been applied to the Experimental Advanced Superconducting Tokamak (EAST) devices, which can in real time, in situ and online monitor the surface composition of wall materials. But there is a challenge to get precisely quantitative result of wall surface in high vacuum environment. The high vacuum environment of EAST device was simulated, and five kinds of samples (nickel base alloy) were ablated by nanosecond pulsed laser to generate plasma and obtain spectra. The temperature and density of plasma were calculated by multi-Boltzmann slope method and Stark width method respectively. The One Point Correction method (OPC) was used to carry out quantitative research comparing with the Calibration-Free LIBS (CF-LIBS) method. The results showed OPC method could significantly improve the quantitative accuracy of each element in the alloy. For matrix element of Ni, the relative error was less than 3.92%. The relative error of Mo with atomic percent of 3.11% decreased from 155.41% to 34.32%. The quantitative method provided a theoretical reference for on-line measurement of impurity deposition on wall surface with LIBS technology.