Characterization and focusing of light ion beams generated by ultra-intensely irradiated thin foils at the kilojoule scale a)

We present the first observations of focused multi-MeV carbon ion beams generated using ultra-intense shortpulse laser interactions with thin hemispherical (400μm radius) targets. The experiments were performed at the Trident laser facility (80 J, 0.6 ps, 2×10²⁰W/cm2) at Los Alamos National Laboratory and at the Omega EP (extended performance) facility (1 kJ, 10 ps, 5×10¹⁸W/cm2) at the Laboratory for Laser Energetics. The targets were chemical vapor deposition diamond, hemi-shells and were heated to remove contaminants. The ion beam focusing was characterized by tracing the projection of a witness mesh in the ion beam on a lithium fluoride nuclear activation detector. From the data, we infer that the divergence of the beam changes as a function of time. We present a 2-D isothermal model to explain the dynamics. We also present discrepancies in the peak proton and carbon ion energies from the two facilities. The implication of which is a fundamental difference in the temporal evolution of the beams from the two facilities. Simulations using the hybrid particle in cell code, Lsp were performed and compared with the experiments.