Laser-driven generation of ultraintense proton beams

The results of experimental and numerical studies of high-intensity proton beam generation driven by a short laser pulse of relativistic intensity are reported. In the experiment, a 350 fs laser pulse of 1.06 or 0.53 μm wavelength and intensity up to 2×1019 Wcm−2 irradiated a thin (0.6–2 μm) plastic (PS) or Au/PS (plastic covered by 0.2 μm Au front layer) target along the target normal. The effect of laser intensity, the target structure and the laser wavelength on the proton beam parameters and laser-protons energy conversion efficiency were examined. Both the measurements and one-dimensional particle-in-cell simulations showed that MeV proton beams of intensity ∼1018 Wcm−2 and current density ∼1012 Acm−2 at the source can be produced when the laser intensity-wavelength squared product I Lλ2 is ∼1019 Wcm−2 μm2 and the laser-target interaction conditions approach the skin-layer ponderomotive acceleration (SLPA) requirements. The simulations also proved that at I Lλ2≥slant 5×1019 Wcm−2 μm2 and λ≤slant 0.53...