Acceleration of L-shell gold ions from sub-micrometer structured foil irradiated by a high-contrast and high-intensity picosecond laser.

Laser-driven heavy ion beams are ideally suited for experiments requiring fast isochoric heating due to the exceptionally high current density of the beams and the high energy deposition rate of the ions. We report here the acceleration of highly charged gold ions (51+ to 61+) up to ~ 400 MeV by laser irradiating sub-micrometer-thick foils as is typical in studies of proton and lighter ion acceleration, without removing the contaminant layer. Microstructures with variable array geometry were 3D-printed on the front surface of the foils to tune the spectral shape and relative number of accelerated ions. The experiment was performed with the PHELIX laser at GSI (Darmstadt, Germany) and the pulses (~150 J, 0.5 ps, 1.054 μm) were focused at ~15º incidence angle on the targets to intensities of ~6×10²⁰ W/cm², with a prepulse contrast ratio of ~10^-12. The high charges and accelerated energies of such low q/m ions (<0.3) were enabled by the very high contrast and sustained pulse duration of the laser, inducing very strong volumetric heating. X-ray line emissions from different target components help elucidate the interaction.