A study of the laser plasma parameters at different laser wavelengths

Diagnostic of laser produced aluminum plasma was performed adopting a spectroscopic technique. A Q-switched Nd:YAG laser at wavelengths 1064, 532 and 355 nm with maximum energies of 500, 100 and 60 mJ, respectively, and pulse duration of 7 ns with repetition rate of 1 Hz was used. The measurements were carried out to determine the spatial electron temperature using the Boltzmann plot for the Al II lines and the spatial profile of the electron density using Stark broadening formula for the three different laser wavelengths. The maximum attainable value of the electron temperature was found at a certain distance away from the target surface depending on the laser wavelength. The electron density reaches its highest value near the target surface. The measurements are then compared with available published experiment and theory and are found to be in agreement with the theory of local thermodynamic equilibrium (LTE).