激光诱导击穿光谱的环形扫描探测与元素分布分析

A Circular Scanning System of Laser-Induced Breakdown Spectroscopy for Tracking the Element Distribution

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。

Laser-induced breakdown spectroscopy(LIBS)is a rapid method for elemental analysis with significant advantages of sample-less,in situ,non-contact,multi-element detection,etc.,and it has been widely applied in many research fields.In this work,LIBS was employed to develop a system for circular scanning,which can obtain the location of the high concentration region of elements according to the distribution acquired from the detection results of scanning.Based on this,an effective,fast and real-time method was provided for environmental anomaly monitoring,pollution source tracking and even mineral exploration.A simple structure was brought in that system to enable 360-degree scanning via rotating optics,not moving the entire system.The position or the orientation of the high concentration region(source)could be tracked by referencing the element distribution,which is related to the signal intensity of LIBS detection.In order to verify the concept of LIBS circular scanning and to evaluate the detectability of the system,seawater fog rich in elements of potassium,calcium,sodium,magnesium was used for the sample to simulate the source eruption.And detection of 360-degree scanning was carried out to evaluate the detection response with an interval of 10 degrees.Experimental results showed that the source position or orientation could be found accurately by following elements distribution,while necessary calibration was required to correct the detection result.The correction procedure includes two aspects:correction of fluctuant data and detection efficiency.The former is used to reduce the signal instability in the process of LIBS detection,mainly through the selection of internal reference elements to modify the signal fluctuation.The latter aims to reduce the errors in the detection process resulting from the installation and debugging and modify the acquisition efficiency of each scanning position according to the detection results in the even atmosphere.The corrected annular scanning data showed that the system could accurately obtain the location of"eruption source"with a large scanning radius(250 and 300 mm).In addition,the exact orientation of the area with a high concentration of elements can be found at a distance from the eruption location with a short scanning radius(100 mm).Therefore,it is suggested that LIBS could be functioning as a"radar"for circular scanning.The distribution of elements obtained through LIBS detection can accurately confirm the exact position of the source by identifying the high concentration region,so as to achieve the purpose of target source tracking.