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激光诱导等离子体光谱仪的研制
Spectrometer Set-up for Laser Induced Plasma Experiment
【作者】 徐国伟；
【导师】 王秋平；
【作者基本信息】 中国科学技术大学 ， 精密机械与精密仪器， 2010， 硕士
【摘要】 激光诱导等离子体光谱技术(LIPS)是一种具有实时在线、非接触、多元素同时探测等优点的元素分析技术,它无需制备样品,分析迅速,是钢铁冶炼中实现在线炉内元素检测的可能方法之一。本文通过将线阵CCD放置于罗兰圆上设计了一台紫外波段的光谱仪样机,其工作光谱波段为235nm~260nm,光谱分辨率达0.14nm。利用该光谱仪搭建的LIPS系统对钢样品中C元素进行检测,通过研究C元素247.84nm处的谱线的相对强度,定性分析了不同钢样品中C元素的含量与谱线相对强度之间的对应关系,实现应用LIPS技术检测钢水中C元素含量的初期实验目的。本文介绍了凹面光栅光谱仪系统和凹面光栅像差理论。根据相关理论,设计了一台基于罗兰圆布置的光栅光谱仪。通过研究光谱仪探测器CCD的像素点与波长的关系,完成了光谱仪的波长标定。采用本文的设计方法,可以通过放置多块线阵CCD,实现凹面光栅罗兰圆分光系统的全波段光谱探测。利用该光谱仪搭建的LIPS系统进行了初步试验,研究了影响LIPS实验结果的相关因素,包括在空气、氩气和氮气不同环境气氛下的激发光谱,分析了其特性形成的原因;通过适当的时间延迟,能明显提高谱线的信噪比,进而提高LIPS分析技术的精度等。
【Abstract】 Laser induced plasma spectroscopy(LIPS)has been shown to be a promising technique for element analysis with many advantages including on-line ,non-contacting and multi-element detection capability. The high speed of analysis and no pretreatment of the sample are a great potential for applications of detection of the elements in steel samples. In this paper we have built a prototype CCD spectrometers, which covers wavelength range 230nm~260nm with spectral resolution of 0.14nm. A LIPS system is establised for the C element detection in the steel sample. By studying spectral intensity of at 247.84nm of C element and at 248.32nm of Fe, the qualitative of C content in steel can be determined. . This paper will discribe the the LIPs system, especially the spectrometer setup to satisfying the spectral resolution for discrimination C and Fe elements. And achieve early experimental purpose of detection of element C’s content in molten steel the by applicating LIPS.This paper describes concave grating spectrometer system and concave grating aberration theory, illustrates design process of grating spectrometer based on the principles of Rowland circle and the optical tracing simulation in detail. The wavelength of the spectrometer is calibrated which describes the CCD pixel position and the the wavelength. By using this design method, we can place the multi-block linear array CCD on the concave grating Rowland circle in order to realize system-wide band spectrum UV detection.Primary LIPS experiments have been done in air, argon and nitrogen enviroment to see the spectrum difference. The influence of delay time after laser plasma is produced on the sample has studied. Differenct delay time for different elment can improve the signal to noise ratio of spectrum and enhance the accuracy of LIPS analysis.