High-Energy Ion Expansion in Laser-Plasma Interactions

Measurements of energetic-ion energy distributions produced from C${\mathrm{D}}_2$ and C${\mathrm{H}}_2$ targets are compared with a numerical model. The model describes the ambipolar expansion of hot electrons and two relatively cold ion species from an electron pressure gradient. For C${\mathrm{D}}_2$ the plasma expansion is adequately represented by a single ion species, whereas for C${\mathrm{H}}_2$ two-ion fluids are required to account for the energy and the relative behavior of the high-energy ion species.