The Radiation Characteristics Research On Laser-induced Mental Plasma

In this paper, the properties of laser-induced plasma spectroscopy of metal radiation werestudied. The laser spectrum analytic system is composed of a high-energy neodymium glasslaser, a multifunctional, a CCD detector, a delay system, and a spectrum collected software.A series of national standard metal were used as the target samples. The main subjects are asthe following:1、Effect of the Carbon Chamber Spatial Confinement on the Metallic Laser Plasma RadiationThe electron temperature and electron density of the plasma were measured by thespectroscopic methods In order to investigate the mechanism of laser-induced plasmaenhanced radiation. Experimental results showed that, when laser plasma was confined by asmall carbon chamber that the height is9.0mm and the internal diameter is4.0mm, thespectral line intensities and signal-to-noise ratio of the sample elements had increaseddramatically. It is thus clear that, the spectral intensities and signal-to-noise ratio oflaser-induced plasma can were improve effectively by using the method of spatialconfinement, which is an effective means for detecting the low-content elements in stainlesssteel samples.2、Effect of Spatial Confinement of Glass Cavity on the stainless steel Plasma RadiationIn experiment, the effects of the glass cavity height variation from sample to plasmaradiation intensity of stainless steel are studied. The electron temperature and electron densityare determined by spectroscopic measurement methods to explain the mechanism forenhanced plasma radiation. Experimental results show that laser plasma radiation intensityhas a trend first weakening and after enhancing when the plasma is bound with a glass cavityis compared with no cavities constraints. The best value is achieved when the glass cavityheight of12mm. The sample elements spectral line Fe, Mo, Co and Ti intensity of nationalstandard stainless steel were increased by90.77%,101.71%,104.27%and60.77%thanwithout cavity constraints, and spectral SNR were improved54.29%,55.30%,59.37%and38.80%, respectively; plasma electron temperature and electron density were increased by1684K and1.8×1016cm-3. Seen, the use of space constraint method can effectively improvethe laser-induced plasma emission spectral intensity and signal to noise ratio for the use oflaser-induced breakdown spectroscopy technique successfully detect low levels of substances in the composition of the foundation.3、Study of self-absorption effect on laser-induced metal plasmaIn order to reduce the effect of spectral line self-absorption on the analysis result in thelaser induced plasma, a plane mirror device is used to constraint the laser plasma, and areasonable explanation is got through comparing the linear evolution under the differentexperimental conditions and measuring the temperature, electronic density and sampleevaporation. The result shows that when the appropriate plane mirror device is used toconstraint the laser plasma, the temperature and the electronic density of the plasma increaseand close to uniform distribution, which can effectively reduce the self-absorption degree ofspectral lines. Therefore, the plane mirror device could reduce the self-absorption effect in thelaser-induced plasma. This makes it possible that choosing a sensitive line as analysis line inthe quantitative analysis of the major elements. In other words, this promotes themeasurement precision in the laser-induced breakdown spectroscopy.4、The detection of the standard steel element Mn and Ni by laser-induced breakdownspectroscopyTo reduce the influence of self-absorption of plasma emission spectra and improve thedetection capability of laser-induced breakdown spectroscopy, a plane mirror device is used toconstraint the laser plasma. The spectral line profile of Mn and Ni in steel samples underdifferent experimental condition are studied and analyzed quantitatively. The experimentalresults demonstrate that the self-absorption of spectral line decreases obviously when a planemirror device is used; through the quantitative analysis of elements Mn and Ni results, thevalue of relative standard deviation of element Mn decreases from3.70%to1.86%, and thatof Ni decreases from6.23%to2.16%, which indicates that the measurements precision isimproved obviously. It is thus clear that the plane mirror device could reduce the adverseeffect of self-absorption on analyzing results obviously.