CHARACTERIZATION OF LASER-GENERATED PLASMA BY ELECTROSTATIC MASS QUADRUPOLE ANALYZER

A study of laser ablation in vacuum of different targets (Al, Ni and Ta) by using 3 ns Nd:YAG laser radiation, at 532 nm wavelength and 109 W/cm2 intensity, is reported. Laser pulse generates a plasma at the target surface and produces high non-isotropic emission of neutral and ion species, which are mainly emitted along the normal to the target surface. Mass quadrupole spectrometry, associated to the electrostatic ion deflection, allows an estimation of the energy distributions and of the emitted charge states, within the plasma plume, as a function of the incident laser energy. Neutrals show typical Boltzmann distributions while ions show Coulomb-Boltzmann-shifted distributions. The plasma is characterized in terms of velocity, kinetic energy, ion charge state and temperature of the ejected particles. A special regard is given to the parameters which influence the plasma properties, such as the free electron density of the ablated elements. The ion acceleration processes occurring inside the plasma, due to the high electrical field generated in the charge non-equilibrium conditions, is also discussed. Introduction – Due to the multitude of photons and particles emission, laser-generate