The Experimental Study And The Theoretical Fitting Of Laser Induced Plasma Emission Spectroscopy

The electron temperature and the electron number density are very important parametersfor plasma. The problem how to determine them has attracted the attention of numerousresearchers . Many scholars commonly use the line broadening method and the Boltzmann plotmethod to determine the electron number density and the electron temperature . However, boththe methods can be only used in the case of the continuous spectrum is very weak relative to thecharacteristic line and the emission spectrum without obvious self-absorption. Tetsuo Sakka etal had described the characteristics of plasma emission and absorption spectrum theory basedon the results of previous studies. Meanwhile, they fitted the experimentally observedself-reversed emission profiles to the model which was based on the calculation ofone-dimensional radiative transfer. And they discussed the impact of various parameters uponcalculated results. A plasma emission model was developed by H.R. Pakhal et al, invokingone-dimensional radiative transfer, to describe the observed emission spectra, meanwhile takinginto account the effect of continuum radiation. Less given parameters were used in such model.The Al plasma temperature and electron number density at different delay times were obtainedby the simulation of the spectra with self-reversed structure.In present paper, by fitting a series of time-resolved laser induced lead plasmaspectroscopy, some work have been done as follows:In experiment, the emission spectra and the images of lead plasma were acquired atdifferent delay times. The lead plasma temperature and the electron number density were got bythe Saha-Boltzmann plot method and the line broadening method respectively.In theory, we used the theory given by H.R. Pakhal et al to fit the emission spectraincluding obvious self-reversed and without obvious self-absorption, determining the electrontemperature, the electron number density and the lower level atomic number density at differentdelay times. Furthermore, these plasma parameters mentioned above were compared when thetarget was at the focus and at 6 mm before it. At the same time, the causes of self-absorptionwere analysed. We used an improved model based on the one given by H.R. Pakhal et al to fit theemission spectra. The effects of different parameters to fitting results were discussedrespectively. The plasma temperature got by Saha-Boltzmann plot method and the electronnumber density got by line broadening method were compared with the fitting results. Theimproved model takes into account the Gaussian distribution of the total particle numbers inplasma interested.