Ion acceleration in expanding multispecies plasmas

The acceleration of light and heavy ions in an expanding plasma slab with hot electrons produced by an intense and short laser pulse is studied by using the hybrid Boltzmann–Vlasov–Poisson model. Spatial profiles, energy distributions, and maximum energies of accelerated ions are analyzed in function of the plasma and hot electron parameters. The crucial parameter for ion acceleration is found to be the ratio of the foil thickness to the hot electron Debye length. Special attention is paid to characterization of protons accelerated from a thin hydrogenated layer at the target surface. The evolution of the proton spectrum is studied for the cases of isothermal and cooling hot electron distributions. The obtained dependencies of the ion energy on the pulse duration and the target characteristics allow one to define the optimal conditions for the ion acceleration with lasers.