Simulation studies of radiation pressure-driven light sail and shock acceleration

Simulation results are reported for two ion acceleration mechanisms driven by radiation pressure. Three-dimensional (3D) simulations of the acceleration of thin foils by circularly polarized pulses ("light sail" regime) at ultra-relativistic intensities (a(0) > 100) show an ion energy that is higher than observed in 1D and 2D simulations, presumably due to density rarefaction and self-wrapping of the laser pulse as the foil is deformed. Simulations of the interaction of linearly polarized pulses with long-scalelength, moderately overdense plasmas at mildly relativistic intensities (a(0) = 1 divided by 10) show radiation-pressure driven formation of both solitary and shock waves leading to ion acceleration in the target bulk. In 1D simulations, the spectrum of the accelerated ions is monoenergetic within some range of the initial ion temperature. In 2D simulations, the onset of rippling at the shock surface apparently leads to broadening of the energy spectrum.