激光诱导击穿光谱的环形扫描探测与元素分布分析

激光诱导击穿光谱(LIBS)作为一种元素快速分析手段,具有无需样品预处理、实时在线、非接触、多元素同时探测等诸多优点,已在多个领域获得应用。搭建了一套可实现环形扫描探测的LIBS光谱探测系统,通过探测结果获得元素分布情况,进而实现元素高浓度区域反演,为环境异常情况监测、污染源追踪甚至矿藏勘察提供一种有效的快速实时分析方法。该系统运行过程中不需要整体移动,只通过旋转部分光学器件即可完成360°全方位的快速扫描与探测,进而以所采集到的光谱强度获知不同扫描角度下的元素分布情况,用于反演元素高浓度区域的具体方位,达到源头位置判定的目的。为验证所提出的LIBS环形扫描设想,评估所搭建系统的探测能力,实验中以海水为探测样品制备富含K,Ca,Na和Mg的喷雾模拟污染源喷发情况,通过标志性元素Na的LIBS光谱强度增长作为目标寻源的主要依据,以每10°为间隔对360°范围内的元素情况进行了扫描探测。实验结果显示该系统能够较为准确地反演出目标源头的具体方位,但需要进行必要的探测结果校正。校正过程具体包括"信号浮动校正"和"探测效率校正"两个方面,前者用于降低LIBS探测过程中信号的不稳定性,主要通过选用内标元素进行信号波动的校正;后者则是减小探测过程中安装调试误差,以环境中均匀分布元素的探测结果完成各扫描位置的光谱采集效率修正。经过校正后的环形扫描数据显示,搭建的系统不仅在大扫描半径(250,300 mm)下能够准确获得"喷发源"位置外,还能够在离喷发位置较远、短扫描半径下(100 mm)明确元素高浓度区域的具体方位。因此,提出的这种适用于LIBS技术的环形扫描探测的硬件结构,实验验证了该结构能够实现近似"雷达"的扫描分析,通过元素光谱信号强度反馈用以实现目标具体方位的判断,进而达到目标寻源的分析目的。

Development of a micro-joule portable LIBS system-and the preliminary results for mineral recognition

Laser-induced breakdown spectroscopy(LIBS) has been extensively applied due to the capabilities of real-time, multi-phase and multi-element analysis. With the advantages, portable LIBS is in rapid development with great potential of field measurements. In this work, a portable LIBS was developed by a 50 μJ level laser for excitation and an objective lens for focusing or imaging. Element detection was successfully achieved by this setup, and also the microscopic observation could be obtained with the magnification of 350×. A preliminary investigation was carried out for mineral recognition by the developed portable LIBS. The obtained results indicate that the element detection combined with micro observation was an effective way for recognizing minerals, especially for similar mineral identification or discrimination. It is suggested that the micro-joule laser could be alternative for the commercial portable LIBS, and the on-site mineral or rock recognition is a promising field for the application.