Radiation effects induced by pulsed laser ablation in tantalum surfaces

An investigation about the pulsed laser irradiation of tantalum surfaces is presented. The employed laser is a Q-switched Nd:Yag, 1064 nm wavelength, with 9 ns pulse width and a maximum power density of 1010 W/cm2. The tantalum shows a high-energy threshold for the ablation, a low etching rate depending on the laser fluence, and a narrow angular emission produced along the normal to the target surface. The irradiation produces an expanding plasma in front of the target. The ion emission is investigated by time-of-flight measurements. The plasma is characterized in terms of average ion velocity and kinetic energy, ion temperature, fractional ionization and ion charge state. A special regard is given to the ion energy distribution and to the charge state distribution, which are presented and discussed.