Highly ordered vertical nickel nanotubes and nanowires on thin substrate for high power lasers experiments

Nanostructured targets showed improved interaction with ultra-intense laser pulses in comparison to planar ones, both in simulations and in experiments. By increasing the surface area, the absorption and conversion efficiency of the laser energy to the accelerated particle energy are enhanced due to volumetric heating, leading to advanced proton acceleration, x-ray emission, ultra-high energy density matter creation, and terabar pressure generation. This work is focused on exploring the limits of the electrodeposition methods for the fabrication of nanostructured targets suitable for ultra-intense laser experiments at focused intensities as high as 10²³W/cm². The geometrical characteristics of the nanostructures are expanded to meet a wide range of experimental requirements: diameter, length, distance between structures, and substrate thickness. Nickel nanotubes and nanowires on few hundreds nanometer thick substrates were fabricated using porous alumina as template, obtained by aluminium anodization in various electrolyte solutions. The resulting structures revealed diameters and spacing of several hundreds of nanometers, with length varying between 1-10 micrometers, covering homogeneous areas of several square centimetres. The influence of temperature on the current density, with two electrolyte mixtures containing oxalic, citric, phosphoric acids used for anodization, is also reported. In the initial testing using high-power lasers, we found an increase in proton energy by 1.5 times and flux at high-energy tail of the spectrum higher by an order of magnitude, from the nanostructured targets.