本文關(guān)鍵詞： LIBS 空間約束 等離子體持續(xù)時(shí)間 兩次增強(qiáng)效應(yīng)　出處：《吉林大學(xué)》2017年碩士論文　論文類型：學(xué)位論文

【摘要】：近年來(lái),激光誘導(dǎo)擊穿光譜(Laser-induced breakdown spectroscopy,簡(jiǎn)稱LIBS)作為一種物質(zhì)元素的分析方法迅速發(fā)展,越來(lái)越被人們所重視。它的原理是用一束高能激光束照射樣品表面產(chǎn)生等離子體,然后利用等離子體光譜分析元素成分。這項(xiàng)技術(shù)具有一個(gè)獨(dú)特的優(yōu)勢(shì)——可以檢測(cè)所有相的樣品(氣體,液體或固體)。同時(shí),也在諸多方面顯示出它的其他優(yōu)點(diǎn):實(shí)時(shí)、原位檢測(cè)、不需要樣品制備等等。由于LIBS技術(shù)擁有上述優(yōu)勢(shì),目前已被應(yīng)用于氣溶膠檢測(cè)、藝術(shù)品診斷、環(huán)境監(jiān)測(cè)、生物制劑等等。隨著激光誘導(dǎo)擊穿光譜技術(shù)的不斷發(fā)展,它的缺點(diǎn)也慢慢暴露出來(lái)——較低的靈敏度,這個(gè)缺點(diǎn)一直阻礙著這項(xiàng)技術(shù)的發(fā)展與實(shí)際應(yīng)用。為此,研究者們提出了許多的方法來(lái)提高光譜的信號(hào)強(qiáng)度,其中空間約束方案表現(xiàn)出獨(dú)特的優(yōu)勢(shì):(1)易實(shí)現(xiàn)、對(duì)系統(tǒng)修改小;(2)能保持等離子體位置的穩(wěn)定;(3)增強(qiáng)等離子體輻射強(qiáng)度的特性。本文內(nèi)容主要分為四個(gè)章節(jié)。第一章,主要介紹LIBS技術(shù)的原理、國(guó)內(nèi)外發(fā)展現(xiàn)狀以及LIBS技術(shù)光譜的增強(qiáng)方法,其中重點(diǎn)討論了空間約束方案;第二章,介紹LIBS技術(shù)的理論背景——等離子體的特性和兩個(gè)基本物理參數(shù);第三章和第四章是本論文的核心,雖然空間約束的LIBS技術(shù)已經(jīng)被眾多研究人員所討論,但是我們將研究方向放在了觀察等離子體原子光譜的持續(xù)時(shí)間上,實(shí)驗(yàn)結(jié)果表明在68m J的激光能量下將約束腔直徑從10mm改變?yōu)?mm,等離子體中Cu(I)線的持續(xù)時(shí)間縮短到了1/5(從25μs到5μs)。因此,約束腔的直徑在激發(fā)中性Cu(I)發(fā)射線的持續(xù)時(shí)間上起著非常重要的作用。然而約束腔的深度幾乎不影響Cu(I)線的持續(xù)時(shí)間,產(chǎn)生這種現(xiàn)象的原因可能是在空間約束下(從10mm改變?yōu)?mm),反射的沖擊波壓縮等離子體并導(dǎo)致在某一延遲時(shí)間處等離子體溫度和密度的增加,使原子進(jìn)一步激發(fā)到更高的激發(fā)能級(jí)。最后,等離子體羽中粒子之間的碰撞幾率增加,原子光譜的持續(xù)時(shí)間減少。同時(shí),還提出了空間約束下兩次增強(qiáng)效應(yīng)的實(shí)驗(yàn)結(jié)果,這種現(xiàn)象是由于反射的沖擊波對(duì)等離子體進(jìn)行壓縮,產(chǎn)生了一個(gè)等離子體溫度較高、激發(fā)原子數(shù)量較多的核心區(qū)域,在此基礎(chǔ)上對(duì)等離子體溫度和電子密度進(jìn)行了計(jì)算;第五章,論文在結(jié)尾部分對(duì)上述的研究工作做出了總結(jié),并給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.
【學(xué)位授予單位】：吉林大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2017
【分類號(hào)】：O53

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