Partial currents of ion species in an expanding laser-created plasma

A novel analysis of ion currents, which is based on the use of shifted Maxwell-Boltzmann velocity distribution, is applied to quantify the properties of expanding laser-produced plasmas into the vacuum. The ion currents were measured outside the critical zone where the recombination and collisional excitation processes are not important and the charge-states of ions are frozen. The deconvolution of single-shot ion currents is applied for recovering the partial currents of participating ion species in the measured ion currents in carbon, copper and polyethylene plasmas created by various pulsed laser beams. This method allows determining the plasma temperature, the centre-of-mass velocities of individual charge-states and their abundance. The obtained charge-state dependencies of the centre-of-mass velocities render important details in establishing the mechanisms responsible for the ion emission, which has fundamental importance in applications of laser ion sources.