An Experimental Investigation On Laser-induced Al Plasma Emission Spectra

The evolution properties of spectral broadness and spectral intensities are obtained by measuring Al space-resolved emission spectra with or without additional electricity field. As a result, the electron densities of plasma in different spatial distances and in various additional voltages are studied. Furthermore, the influence of power density to the spectral broadness and the spectral intensities are discussed. The main content includes:(1) The electron density of laser induced Al plasmas.By using 1.06μm pulse laser produced by Nd:YAG laser ablation, the space resolved emission spectra were gotten under low air pressure. The electron density of Al plasma was calculated by measuring the Stark broadness of line. The spatial distribution of electron density was studied. It reaches its highest value near the target surface, and reduces with the distance increasing from target surface. Recombination radiation is considered to be the primary reason for the reducing electron density, and to a certain extent the experiment result is to be explained by it. The effects of laser pulse energy on the electron density were studied as well.(2) Emission spectroscopic studies of Laser-induced Al Plasma in additional electric field.The emission spectrum of Al plasma produced by ablating Al target with Q-switch Nd:YAG Laser(wavelength 1.06μm, pulse width 10 ns) is observed under a low air pressure and direct electricity field. The intensity and the broadness of spectral line in various additional voltages are measured, the result of which shows that the intensity and the broadness of spectral line of Al atom are increasing prominently with the additional voltage increasing, but there is little influence on both intensity and broadness of ion spectral line. The collision between atoms and electrons moving in a definite direction with the additional static electric field is considered to be the primary reason for the result mentioned above. In addition, the effects of the additional voltage on the electron density are also discussed.