Spectral and spatial ion beam parameter optimization at petawatt laser facilities

We demonstrate that tailoring the laser–target interaction at the PW-class VEGA-3 facility (by controlling the focusing conditions, pulse duration, chirp sign and solid-target properties) enables the enhancement of ion flux, divergence and cutoff energy for high-energy-density physics experiments. The existence of optimal pulse duration, focusing conditions, target thickness and target material is experimentally demonstrated. We further show that a reduction in ion acceleration efficiency under best-compression conditions leads to delayed relative depletion of the hydrogen population compared to carbon ions, accompanied by a decrease in both ion flux and cutoff energy. For metallic targets, scintillator detectors reveal a more divergent and deflected proton beam than that produced from thick plastic targets. The product of the magnetic field strength and the interaction length acting on the ions is estimated to reach up to 400 MG μm, resulting in a ring-like spatial distribution of protons generated from aluminum and copper targets.