激光作用金屬誘導(dǎo)等離子體行為分析

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摘要 激光誘導(dǎo)等離子體光譜分析（LIPS）技術(shù)是一種新型的技術(shù)的用來分析物質(zhì)的元素構(gòu)成。與傳統(tǒng)的分析方法相比較，激光等離子體光譜分析方法具有操作簡(jiǎn)單，元素分析所需時(shí)間短，分析用到的樣品量非常小，對(duì)樣品幾乎無損傷等優(yōu)點(diǎn)，結(jié)合光纖技術(shù)還可以實(shí)現(xiàn)遠(yuǎn)距離操作。激光誘導(dǎo)等離子體光譜技術(shù)已經(jīng)被廣泛的運(yùn)用到冶金工業(yè)、環(huán)境監(jiān)測(cè)、宇宙探索和醫(yī)學(xué)制藥等領(lǐng)域。
本文回顧了近幾年各國(guó)學(xué)者在這項(xiàng)技術(shù)方面的研究取得的成果，介紹了等離子體的概念，激光誘導(dǎo)等離子體產(chǎn)生原理和實(shí)驗(yàn)分析需滿足的兩個(gè)前提條件。本實(shí)驗(yàn)將Nd:YAG激光器產(chǎn)生的激光聚焦到鐵樣品表面，延遲時(shí)間設(shè)為700ns，用Mechelle光譜儀記錄了等離子體產(chǎn)生的輻射。著重研究了不同激光脈沖能量下（分別為3J、4J、5J、6J、7J）的等離子體譜線圖。利用Boltzmann繪圖法，擬合計(jì)算得到的各個(gè)點(diǎn)，獲得擬合直線斜率，由此計(jì)算出等離子體中的電子溫度；使用Stark展寬法，通過洛倫茲函數(shù)擬合對(duì)實(shí)驗(yàn)得到的譜線進(jìn)行處理，獲取特征譜線半高全寬由此計(jì)算得到等離子體的電子數(shù)密度。對(duì)等離子體的電子數(shù)密度和溫度與激光的脈沖能量改變的變化趨勢(shì)進(jìn)行分析，可以看出隨著激光能量逐漸增加，電子溫度和電子數(shù)密度總體上是逐漸增加的，但是在等離子體屏蔽效應(yīng)的影響下，不同脈沖能量下的等離子體電子溫度和密度的增長(zhǎng)趨勢(shì)呈現(xiàn)出先快后慢再快的規(guī)律。

關(guān)鍵詞：激光誘導(dǎo)等離子體 電子溫度 電子數(shù)密度 激光脈沖能量



Behavior Analysis of Laser-Induced Metal Plasmas

Abstract Laser-induced plasma spectroscopy (LIPS) is a new technology of material element analysis. This technique has lots of advantages when we compare it with the traditional analysis method. For example, its operation is simple, we can quickly get the result of analysis and there is almost no damage to the sample. We can realize remote-controlled operation if we take the help of fiber. The laser-induced plasma spectroscopy has been widely applied to metallurgical industry, environment monitoring, space exploration and medicine pharmacy, etc.
The present paper reviews the achievements of LIPS which are achieved by the international scholars in recent years. This paper also introduces the concept and generation principle of laser-induced plasma. We should meet two conditions in this experiment. We focus the Nd: YAG laser (wavelength 1064 nm) on iron samples, we use an Echelle spectrograph to record the plasma emissions. The delay time we set is 700 ns. We mainly study the plasma spectrum under different laser pulsed energy (3J, 4J, 5J, 6 J, 7J) in this paper. The value of temperature T can be determined from the slope of Boltzmann plot；We use the Stark broadening method for determining the electron number density ne, which need using Lorentz fitting for calculating the half-width of the plasma emission. When we analyze the plasma electron temperature and electron number density, we get their change trend along with the laser pulse energy, from which we can find that when laser energy is increasing, the plasma electron temperature and density is gradually increasing on the whole. However, due to the effect of plasma shielding, the plasma electron temperature and density under different pulse energy has different growth trend, which is fast at beginning, then becomes slowly and fast at the end.

Keywords laser-induced plasma electron temperature electron number density laser pulse energy

目錄
摘要 1
第一章 緒論 1
1.1課題研究背景和研究意義 1
1.2激光等離子體光譜技術(shù)的發(fā)展和研究現(xiàn)狀 2
1.2.1激光誘導(dǎo)等離子體的發(fā)展歷史 2
1.2.2國(guó)內(nèi)外的研究成果 2
1.3 本文研究?jī)?nèi)容 7
第二章 激光誘導(dǎo)等離子體的基本原理 9
2.1等離子體含義 9
2.2等離子體產(chǎn)生機(jī)理 9
2.3研究等離子體性質(zhì)應(yīng)滿足的兩個(gè)假設(shè)條件 10
2.4激光誘導(dǎo)等離子體的電子體溫度計(jì)算 10
2.5等離子體電子數(shù)密度計(jì)算 12
第三章 實(shí)驗(yàn)裝置及結(jié)果分析 14
3.1實(shí)驗(yàn)裝置原理圖 14
3.2實(shí)驗(yàn)結(jié)果與分析 15
3.2.1不同能量密度下譜線相對(duì)強(qiáng)度的變化 17
3.2.2不同能量密度下等離子體溫度的變化分析 18
3.2.3等離子體電子數(shù)密度隨激光脈沖能量的變化分析 21
3.2.4局部熱運(yùn)動(dòng)平衡分析 24
第四章 總結(jié)與展望 26
致謝 28
參考文獻(xiàn) 29