A new method for calculation of thick plasma parameters by combination of laser spectroscopy and shadowgraphy techniques

Abstract

In this paper, a new method is introduced for studying optically thick plasma in local thermodynamic equilibrium condition by laser induced breakdown spectroscopy (LIBS) technique. The method presented here is very simple, exact, and appropriate for simultaneously quantifying the plasma parameters and instrumental function of the experimental system from self-absorbed spectral lines. A LIBS experiment is performed on an aluminum target in air atmosphere by combination of two techniques of shadowgraphy and spectroscopy, and by utilizing a theoretical approach. In this work, plasma parameters can be accurately calculated when the electron density, plasma length and intensities of three spectral lines are experimentally known. This model suggests that instead of using two spectral lines in thin plasmas, three lines are required in thick plasmas for exactly estimating the plasma temperature. In this paper, the temporal evolution of plasma dynamics, such as the number densities of the emitting species, plasma length, velocity of plasma expansion and its temperature variation is obtained by the presented procedure.