Gerard O'Sullivan

We have demonstrated angular distribution separation of the extreme ultraviolet (EUV) emission and suprathermal ions with a significant energy reduction for ions produced using dual pulse irradiation of a planar gadolinium (Gd) target. The pulse separation time between the pre-pulse and the main laser heating pulse was set at 30 ns, and the pre-plasma was irradiated at a distance of 50 μm above the target. Angular distributions of the EUV emission and the suprathermal ions were almost isotropic and followed a cos4θ distribution, respectively. The suprathermal ions were emitted normal to the target along the pre-pulse laser axis. The most probable energy of the suprathermal ions was less than 2 keV, while their maximum charge state was Gd6+ with the pre-plasma, compared to an energy of about 10 keV with a maximum charge state Gd15+ without the pre-plasma. The results suggest that the collector mirror position may be chosen to achieve a long lifetime, by avoiding damage from fast ion collisions.