被动调Q激光诱导击穿光谱探测研究

发布时间：2018-06-25 08:25

本文选题：激光诱导击穿光谱 + 等离子体　；参考：《哈尔滨工业大学》2017年硕士论文

【摘要】：激光诱导击穿光谱技术(Laser-Induced Breakdown Spectroscopy,简称LIBS)是一种通过使用高能激光脉冲来激发样品,并探测接收样品原子发射光谱的技术。聚焦激光脉冲和样品之间的相互作用产生了由电离物质组成的等离子体,等离子体发射的光谱可以提供多种不同化学成分元素专属的“光谱指纹”,检测过程相对简单,能检测分析很多物理形态下的样品,对很多ppm量级元素有很好的检测灵敏度,而且只消耗少量样品(通常只有pg~ng量级形成等离子体)进行分析,在检测时通常可近似为无损检测,利用无需样品预处理的优势可进行遥感探测。首先,搭建了实验室常规使用的,基于主动调Q激光器的单脉冲LIBS光谱探测系统,使用DG535数字延时信号发生器,将激光器和光谱仪进行同步,时间分辨光谱数据,找到最佳信噪比延迟时间;其次,搭建了基于被动调Q激光器的单脉冲LIBS系统,设计了小型光电转换模块及数字延时模块,使用泵浦氙灯作为触发信号进行光谱采集同步,找到最佳工作条件;最后,搭建了基于被动调Q激光器的预烧蚀双脉冲LIBS系统,泵浦氙灯电压达到570V时,稳定出输出双脉冲激光,双脉冲间隔35μs~40μs,将第一束脉冲激光的漫反射光作为触发信号,经光电转换及数字延时后进行光谱采集同步,找到最佳工作条件。分别使用上述三种LIBS系统进行样品烧蚀实验对比。首先,对纯铜样品进行烧蚀,三种LIBS系统都可以得到纯铜样品光谱,双脉冲LIBS系统可以得到信噪比更高,强度更强的光谱谱线;其次,使用内部标定法对溶液中铜离子进行检测分析,将500ppm的MgCl_2溶液作为内标溶液,检测不同浓度的CuCl_2溶液,以碳棒为基底,在水分蒸发后进行烧蚀分析,得到双脉冲LIBS系统对Cu元素的检测限为5.87ppm;最后,对海水进行元素光谱检测,两种单脉冲LIBS系统只能检测到海水中含量较高的元素,被动调Q双脉冲LIBS系统可以检测出更多的元素,分别对威海小石岛地区和麻子港生活污水入海口处的海水进行检测分析,发现麻子港处的Al、Fe、Cu元素含量相对较高,也说明生活污水中上述元素含量相对较高。
[Abstract]:Laser-Induced Breakdown Spectroscopy (LIBS) is a technique that excites samples by using high-energy laser pulses and detects atomic emission spectra of receiving samples. The interaction between the focused laser pulse and the sample produces a plasma consisting of ionized substances. The spectrum emitted by the plasma can provide a "spectral fingerprint" that is specific to many different chemical elements, and the detection process is relatively simple. Can detect and analyze samples in many physical forms, have good sensitivity for many ppm orders of magnitude, and consume only a few samples (usually only pg~ng order of magnitude to form plasma) for analysis. In the detection process, it can be approximated as nondestructive testing, and remote sensing detection can be carried out by using the advantage of no sample pretreatment. First of all, a monopulse Libs spectral detection system based on active Q-switched laser is set up in the laboratory. The DG535 digital delay signal generator is used to synchronize the laser with the spectrometer and resolve the spectral data in time. The optimal SNR delay time is found. Secondly, a monopulse Libs system based on passive Q-switched laser is built, and a small photoelectric conversion module and a digital delay module are designed. The pump xenon lamp is used as the trigger signal for spectral acquisition synchronization. Finally, a pre-ablation double-pulse Libs system based on passive Q-switched laser is built. When the pump xenon lamp voltage reaches 570V, the output double-pulse laser is stabilized. The diffuse reflectance of the first pulsed laser is taken as the trigger signal, and the spectrum acquisition synchronizes after photoelectric conversion and digital delay, and the optimum working conditions are found. The above three Libs systems were used to compare the sample ablation experiments. First, the pure copper sample can be ablated, the spectrum of pure copper sample can be obtained by three kinds of Libs system, and the spectral lines with higher SNR and stronger intensity can be obtained by double pulse Libs system. The copper ions in the solution were detected and analyzed by internal calibration method. The 500ppm MgCl2 solution was used as the internal standard solution to detect the CuCl2 solution with different concentrations. The carbon rod was used as the substrate, and the ablation analysis was carried out after the evaporation of the water. The detection limit of Cu in dual-pulse Libs system is 5.87 ppm.Finally, the two monopulse LIBS systems can only detect the elements with high content in seawater. The passive Q-switched dual-pulse Libs system can detect more elements. The seawater in Xiaoshi Island area of Weihai and at the entrance of domestic sewage of Aizi Port has been detected and analyzed respectively. It is found that the content of Al _ (Fe) Fe _ (Cu) in the port is relatively high. It also shows that the content of above elements in domestic sewage is relatively high.
【学位授予单位】：哈尔滨工业大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：O657.319

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