Dynamics of aluminum plasma produced by a nitrogen laser

Abstract

13mJ laser pulses from a nitrogen laser were focused onto an aluminum target in air. The target surface was perpendicular to the axis of the laser beam. A peak energy density of 1.3 J/cm2 and a power density of 80 MW/ anz were achieved with a laser pulse duration of 1611s. The high power density produced a transient plasma cloud that expanded explosively into the surrounding atmosphere. An initial electron density of about 1 x 10'9cm3 and an electron temperature of about 2eV were determined by optical spectroscopy. The line of sight was parallel to the surface and perpendicular to the laser beam axis. The height of the line of sight above the target surface was varied in order to gather data about the whole plasma cloud. In about 50011s the plasma cloud expands to about OSmm above the target surface, cools down to about 1.2eV and is tenfold reduced in electron density. The initial expansion velocity was determined to be about 2 km/s. The experimentally determined plasma parameters were input into numerical models of target heating and plasma expansion. The numerical results outrule the so called outflow model of plasma expansion and show reasonable agreement with an effusion model. The observed discrepancies in observed and calculated plasma parameters are attributed to the fact that the theoretical models describe the plasma expansion in vacuum only.

Characterization of laser-ablation plasmas

“…Time-and space-resolved spectroscopic measurements. Time-resolved spectroscopy was employed by Andreic et al (1993) to study optical plasma emission in the UV-visible spectral region (240-550 nm) in the case of laser ablation of Al targets. Spectral lines of successive ionization stages were used, since in this case the energy difference between the upper levels of the lines is increased by the ionization energy of the lower ionization stage.…”

Laser-induced plasma electron number density: Stark broadening method versus the Saha–Boltzmann equation

“…The limitation of this technique is the availability of the W value database which is very limited [1,2,22,23]. Again no uncertainties have been reported for W values in the literature for Al lines, but Ortiz et al reported an uncertainty of ∼20% for W values of Au(I) lines [24].…”

Investigations on nanosecond laser produced plasma in air from the multi-component material YBa2Cu3O7

“…Considerable efforts are being made worldwide in plasma diagnostics and in studying the dynamics of laser-target interactions [13][14][15][16][17][18][19][20][21][22]. Among the various plasma parameters, the plasma temperature and the plasma electron and ion densities are the main quantities that determine the plasma characteristics.…”