2008 Volume 3 Pages 035
We investigate ion energy spectra of a droplet target composed of different ion species, which is assumed to be heated by ultrashort laser pulse. The dynamics is studied with three-dimensional particle-in-cell simulation. It is found that the maximum ion energy Ei,max of the ion species with a charge a state Z has proportionality, Ei,max ∝ Z2 , when multi-species ions exist in large quantities simultaneously. This is a crucial new result different from the scaling Ei,max ∝ Z, where the fraction of such contaminating ions is small compared with that of the background ions. We discuss this present numerical result by comparing with a self-similar solution, which takes a full account of the charge separation effect.