Nanostructured target fabrication with metal and semiconductor nanoparticles

The development of ultra-intense high-energy (1 J) short (<1 ps) laser pulses in the last decade has enabled the acceleration of high-energy short-pulse proton beams. A key parameter for enhancing the acceleration regime is the laser-to-target absorption, which heavily depends on the target structure and material. In this work, we present the realization of a nanostructured target with a sub-laser wavelength nano-layer in the front surface as a possible candidate for improving the absorption. The nanostructured film was realized by a simpler and cheaper method than using conventional lithographic techniques: A colloidal solution of metallic or semiconductor nanoparticles (NPs) was produced by laser ablation and, after a heating and sonication process, was spray-dried on the front surface of an aluminum target. The obtained nanostructured film with a thickness of 1 μm appears, at morphological and chemical analysis, uniformly nanostructured and distributed on the target surface without the presence of oxides or external contaminants. Finally, the size of the NPs can be tuned from tens to hundreds of nanometers simply by varying the growth parameters (i.e., irradiation time, fluence, and laser beam energy).