激光诱导等离子体LTE态判定方法研究  

Research on the Identification Method of LTE Condition in the Laser-Induced Plasma

作　　者：樊娟娟[1] 黄丹[1] 王鑫[1] 张雷[1] 马维光[1] 董磊[1] 尹王保[1] 贾锁堂[1] 

机构地区：[1]量子光学与光量子器件国家重点实验室、山西大学激光光谱研究所,山西太原030006

出　　处：《光谱学与光谱分析》2014年第12期3183-3187,共5页Spectroscopy and Spectral Analysis

基　　金：国家重点基础研究发展计划(973计划)项目(2012CB921603);国家自然科学基金项目(61127017,61178009,61108030,61378047,61275213和61205216);国家科技支撑计划项目(2013BAC14B01);山西省青年科学基金项目(2013021004-1,2012021022-1);长江学者和创新团队发展计划项目(IRT13076);山西省专利推广实施项目(131002);山西省回国留学人员科研项目(2013-011);山西省留学回国人员科技活动资金项目(2013-01)资助

摘　　要：针对目前等离子体温度测量中常用的Boltzmann平面法和双线法的测量精度较差的问题,提出结合Boltzmann-Maxwell分布和Saha-Eggert公式来提高等离子温度的测量精度;根据高斯公式的面积与峰值关系建立了发射谱线线宽的简便算法,并通过谱线的Stark展宽计算等离子体的电子密度;建立了以McWhirter准则的等离子局部热平衡（LTE）态判据。以铝为被测样品的实验结果表明,随着激光能量的增加,等离子体温度和电子密度随之呈线性上升趋势;激光能量在127~510mJ范围内的等离子体电子密度变化范围为1.305 32×10^17~1.873 22×10^17 cm^-3,等离子体温度的变化范围为12 586~12 957K,根据McWhirter准则本实验中所有等离子体均满足LTE态阈值条件;针对在光谱仪波段内可观测到的处于同一电离态谱线相对较少的铝元素,在不适合用Boltzmann平面法计算温度时,利用Saha-Boltzmann方法对100组铝等离子体光谱进行温度测量的相对标准偏差（RSD）为0.4%,相比于双线法的1.3%,大幅提高了测量精度。该计算方法可用于快速计算等离子体温度、电子密度及判断等离子体LTE态,在自由定标、光谱有效性分析、谱线的温度校正、确定最佳采光位置以及等离子体LTE分布状态等研究中都有较高的应用价值。Because of the poor accuracy of the commonly used Boltzmann plot method and double-line method,the BoltzmannMaxwell distribution combined with the Saha-Eggert formula is proposed to improve the measurement accuracy of the plasma temperature;the simple algorithm for determining the linewidth of the emission line was established according to the relationship between the area and the peak value of the Gaussian formula,and the plasma electron density was calculated through the Stark broadening of the spectral lines;the method for identifying the plasma local thermal equilibrium（LTE）condition was established based on the McWhirter criterion.The experimental results show that with the increase in laser energy,the plasma temperature and electron density increase linearly;when the laser energy changes within 127~510mJ,the plasma electron density changes in the range of 1.305 32×10^17~1.873 22×10^17 cm^-3,the plasma temperature changes in the range of 12 586~12 957 K,and all the plasma generated in this experiment meets the LTE condition threshold according to the McWhirter criterion.For element Al,there exist relatively few observable lines at the same ionization state in the spectral region of the spectrometer,thus it is unable to use the Boltzmann plane method to calculate temperature.One hundred sets of Al plasma spectra were used for temperature measurement by employing the Saha-Boltzmann method and the relative standard deviation（RSD）value is 0.4%,and compared with 1.3% of the double line method,the accuracy has been substantially increased.The methods proposed can be used for rapid plasma temperature and electron density calculation,the LTE condition identification,and are valuable in studies such as free calibration,spectral effectiveness analysis,spectral temperature correction,the best collection location determination,LTE condition distribution in plasma,and so on.

关 键 词：激光诱导等离子光谱 局部热平衡态 Saha-Boltzmann方法 

分 类 号：O433.5[机械工程—光学工程]