Stable laser-ion acceleration in the light sail regime

Abstract

We present experimental results on ion acceleration with circularly polarized, ultrahigh contrast laser pulses focused to peak intensities of 5×10^{19} W cm^{-2} onto polymer targets of a few 10 nanometer thickness. We observed spatially and energetically separated protons and carbon ions that accumulate to pronounced peaks around 2 MeV containing as much as 6.5% of the laser energy. Based on particle-in-cell simulation, we illustrate that an early separation of heavier carbon ions and lighter protons creates a stable interface that is maintained beyond the end of the radiation pressure dominated acceleration process.