Temporal behavior of the tungsten plasma produced by 1064 nm pulsed Nd-YAG laser

A time-resolving Langmuir probe was used to investigate the expansion of tungsten plasma produced by the pulsed Nd-YAG laser (wavelength = 1064 nm, pulse duration = 10 ns). Current–voltage (IV) plots at various times after the laser shot hit the target were obtained from probe electron and ion currents. Langmuir probe theory was used to determine the temporal variation of the plasma potential, electron temperature and electron density. These plasma parameters sharply rise to a maximum value and then slowly decrease during the plume expansion. For the laser irradiance of 10.88 × 108 W/cm2, maximum values of plasma potential, electron temperature and electron density were about 24 V, 15.8 eV and 2.24 × 1016 cm−3 respectively. The measurements performed with time-of-flight electrostatic energy analyzer confirmed the presence of highly charged tungsten ions in the plasma and charge state of ions found to increase with the laser irradiance.