Fig. 4: Simulation results revealing multiple acceleration contributions in different directions.
From: Laser-driven high-energy proton beams from cascaded acceleration regimes
a, Proton energy spectra extracted from 3D particle-in-cell simulation for different spatial directions. b, Simulation results of proton emission distribution. Only protons in the central slice of ±1 µm around the symmetry plane within a vertical emission range of ±3° are shown. c, Angularly resolved contribution of different mechanisms to the acceleration cascade of the fastest protons (orange, CR; dark green, thermal, diffuse sheath field set up by thermal and recirculating electrons; light green, prompt, j × B accelerated electron bunches; blue, FSA, target front and bulk acceleration; see Supplementary Fig. 2 for details). The right panel shows the individual energy contribution of each mechanisms for two selected directions (0° and 45°). d, Time history of the electric field Ex along the propagation direction x of the most energetic tracer proton. The trajectory of this proton is depicted by the thick black line. The contour of the relativistically corrected critical density (γ nc) of the target is shown by the thin black line.
