Studying the Role of Ambient Conditions in Laser Induced Al-Plasma Expansion

The role of ambient conditions on the spatial and temporal evolution of the aluminum plasma spectral emission is studied. Measurements were carried out in vacuum as well as in air at atmospheric pressure to determine the optimum value of both distances from target and of the delay time at which the spectral line emission is most intense. The plasma is generated using a Q-switched Nd:YAG laser at a wavelength of 532 nm and a pulse duration of 8 ns. The analysis revealed that the intensities of the spectral atomic line (305.00 nm) and the ionic line (281.61 nm) were strongly enhanced in air. Moreover, the plasma expansion velocity was determined using a time-of-flight (TOF) measurements technique. Within the experimentally investigated distance range, its peak value was found to be descending from 1.2 × 105 cm/sec and 5.1 × 104cm/sec in air while in vacuum, it was ascending from 5.0 × 105cm/sec 2.5 × 106cm/sec. In addition, these measurements enabled us to determine the temporal and spatial evolutions of the electron temperature and the electron density by using a Boltzmann plot and a Stark broadening profile, respectively. The estimated values of both the electron temperature and the electron density showed an exponential decrease with time, ending with a leveling off behavior. KCI Citation Count: 7