Emission Lines Characteristics Of Laser Induced Ti Plasma

In1962,Brech[1]first put forward the spectrochemical method generating plasma inducedby the ruby maser, which is the predecessor of laser induced breakdown spectroscopy.LIBShas gained rapid development in the past fifty years. Compared with the traditional spectrummeasurement technology, laser induced plasma has the characteristics of high temperature andhigh density and the advantages of real time analysis, fast, no need for sample pretreatment,unrestricted research object and small possibility of recontamination, convenient technicalanalysis without sample pretreatment. The applications of LIBS have become the focus of theresearch and themes in the recent20years, which include the fields of industrial productioncontrol and quality assurance, environmental protection, industrial process analysis, gascomponent, surface chemical imaging, alien probe, biomedical, cultural heritage protection, andsurface cleaning.Characterization of the laser-induced plasma parameters such as electron temperature,electron density and broadening has attracted the interest of more and more researchers inrecent years. We can gain further understanding of the reaction mechanism through diagnosticsof plasma parameters. Ti as a sample was used in my experiment, and some of thecharacteristics of Ti plasma were obtained by the diagnosis of the emission lines of the Tiplasma in this paper. We firstly studied the spatial and temporal evolution of the line intensities,as well as the relationship with the laser energy. At the same time, two methods of measuringthe electron temperature were introduced which include the Boltzmann and Saha-Boltzmannmethods. The electron temperature was calculated respectively in the article by two methodsand analyzed the reasons for the difference. Also for the Boltzamnn method, the electrontemperature was also different using atom and ion spectral lines respectively and the reasonswere explained in the article. The parameters of line broadening and electron density were alsodiagnosed. The spatial and temporal evolution of the two both parameters follow similar laws.The self-absorption phenomenon of certain spectral lines is obvious when the plasma isoptically thick, and the self-absorption has greater effect on plasma diagnostics when usingLIBS. The plasma is usually seen as uniform plasma and the self-absorption is generally not beconsidered which makes it impossible to fully reflect the microscopic characteristics of theplasma, leading to a big gap with the actual results. Several methods of studying thephenomenon of self-absorption at present were introduced in the sixth chapter and provided areference for how to weaken the influence of self-absorption in the experiment.