Electrical field measurements in non-equilibrium laser-generated plasmas

Summary form only given. A Nd Yag laser, operating at 1064 nm wavelength, 9 ns pulse duration, 900 mJ maximum pulse energy, single shot, is employed to ablate metallic targets (Sn, Au) placed in high vacuum (10-7 mbar). Time-of-flight measurements, performed with ion collectors and an electrostatic ion energy analyser, permit to calculate the ion velocity, kinetic energy and charge states. Plots of ion energy distributions, as a function of the ion charge state, demonstrate that Coulomb-Boltzmann shifted distributions are produced as result of thermal processes and electrostatic ion interactions. In particular, ions are accelerated along the normal to the target surface by high electrical field acting for times comparable with the laser pulse duration. The electrical field intensity is calculable through the ion energy shift and the Debye length of the plasma developed at the target surface. Electrical field measurements, of the order of tens of MV/cm, are calculated and discussed