空间约束下激光诱导铜等离子体光谱研究

发布时间：2018-02-05 22:43

本文关键词： LIBS 空间约束等离子体持续时间两次增强效应　出处：《吉林大学》2017年硕士论文　论文类型：学位论文

【摘要】：近年来,激光诱导击穿光谱(Laser-induced breakdown spectroscopy,简称LIBS)作为一种物质元素的分析方法迅速发展,越来越被人们所重视。它的原理是用一束高能激光束照射样品表面产生等离子体,然后利用等离子体光谱分析元素成分。这项技术具有一个独特的优势——可以检测所有相的样品(气体,液体或固体)。同时,也在诸多方面显示出它的其他优点:实时、原位检测、不需要样品制备等等。由于LIBS技术拥有上述优势,目前已被应用于气溶胶检测、艺术品诊断、环境监测、生物制剂等等。随着激光诱导击穿光谱技术的不断发展,它的缺点也慢慢暴露出来——较低的灵敏度,这个缺点一直阻碍着这项技术的发展与实际应用。为此,研究者们提出了许多的方法来提高光谱的信号强度,其中空间约束方案表现出独特的优势:(1)易实现、对系统修改小;(2)能保持等离子体位置的稳定;(3)增强等离子体辐射强度的特性。本文内容主要分为四个章节。第一章,主要介绍LIBS技术的原理、国内外发展现状以及LIBS技术光谱的增强方法,其中重点讨论了空间约束方案;第二章,介绍LIBS技术的理论背景——等离子体的特性和两个基本物理参数;第三章和第四章是本论文的核心,虽然空间约束的LIBS技术已经被众多研究人员所讨论,但是我们将研究方向放在了观察等离子体原子光谱的持续时间上,实验结果表明在68m J的激光能量下将约束腔直径从10mm改变为2mm,等离子体中Cu(I)线的持续时间缩短到了1/5(从25μs到5μs)。因此,约束腔的直径在激发中性Cu(I)发射线的持续时间上起着非常重要的作用。然而约束腔的深度几乎不影响Cu(I)线的持续时间,产生这种现象的原因可能是在空间约束下(从10mm改变为2mm),反射的冲击波压缩等离子体并导致在某一延迟时间处等离子体温度和密度的增加,使原子进一步激发到更高的激发能级。最后,等离子体羽中粒子之间的碰撞几率增加,原子光谱的持续时间减少。同时,还提出了空间约束下两次增强效应的实验结果,这种现象是由于反射的冲击波对等离子体进行压缩,产生了一个等离子体温度较高、激发原子数量较多的核心区域,在此基础上对等离子体温度和电子密度进行了计算;第五章,论文在结尾部分对上述的研究工作做出了总结,并给出了下一步的工作展望。
[Abstract]:In recent years, Laser-induced breakdown spectroscopy (Libs) has been developed rapidly as a material element analysis method, and has been paid more and more attention. Its principle is to produce plasma on the surface of sample with a beam of high energy laser beam. The technique then uses plasma spectroscopy to analyze elemental composition. This technique has a unique advantage in detecting samples of all phases (gas, liquid, or solid). At the same time, it shows its other advantages in many ways: real time. LIBS technology has been used in aerosol detection, art diagnosis, environmental monitoring, biological agents and so on. With the development of laser induced breakdown spectroscopy, Its shortcomings have been slowly exposed-low sensitivity, which has been hampering the development and practical application of the technology. To this end, researchers have proposed a number of ways to improve the signal intensity of the spectrum. Among them, the space confinement scheme shows a unique advantage: 1) easy to realize, and the modification of the system can keep the stability of the plasma position. (3) enhance the radiation intensity of the plasma. This paper is mainly divided into four chapters. This paper mainly introduces the principle of LIBS technology, the development status at home and abroad, and the enhancement method of LIBS spectrum, in which the spatial confinement scheme is discussed emphatically, the second chapter introduces the theoretical background of LIBS technology-the characteristics of plasma and two basic physical parameters. Chapters 3 and 4th are the core of this thesis. Although spatially constrained LIBS technology has been discussed by many researchers, we focus on the duration of plasma atomic spectra. The experimental results show that at the laser energy of 68mJ, the duration of the Cui line in the plasma is shortened to 1 / 5 (from 25 渭 s to 5 渭 s) by changing the diameter of the confined cavity from 10 mm to 2 mm. The diameter of the confinement cavity plays a very important role in the duration of the excitation of the neutral Cu-I line, but the depth of the confined cavity has little effect on the duration of the Cu-I line. This phenomenon may be due to space constraints (from 10mm to 2mm), when the reflected shock wave compresses the plasma and results in an increase in the temperature and density of the plasma at a certain delay time. Finally, the collision probability between particles in the plasma plume is increased and the duration of atomic spectrum is reduced. At the same time, the experimental results of two enhancement effects under space constraints are presented. Because the reflected shock wave compresses the plasma, it produces a core region with higher plasma temperature and more excited atoms. On this basis, the plasma temperature and electron density are calculated. In chapter 5th, the conclusion of the paper summarizes the above research work, and gives the future work prospect.
【学位授予单位】：吉林大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：O53

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