Ionic and atomic characterization of laser-generated plasmas at 5 × 109 W/cm2 pulse intensity

A Nd:YAG laser operating at 1064 nm wavelength, 150 mJ pulse energy and 3 ns pulse width, was employed to produce a non-equilibrium plasma by ablating several different targets (silicon, titanium, copper and germanium) at 5 × 109 W/cm2 pulse intensity. The ion emission from the plasma was monitored through time-of-flight (TOF) measurements, performed by using an ion collector (IC) placed along the normal to the target surface. The deconvolution of the IC experimental spectra with a Coulomb–Boltzmann-shifted function permitted to evaluate the equivalent ion temperature and acceleration voltage, and the mean ion charge state developed inside the non-equilibrium plasma. A classical mass quadrupole spectrometer (MQS) was employed to detect ion charge states and plasma neutrals at various detection angles. The plasma fractional ionization, the ions and neutrals angular distribution and the ablation yield, as estimated through a MQS calibration process, were also evaluated.