Increased electron, positron, and x-ray production from high intensity laser interactions using micro-wire targets

We report increases in energetic electrons, positrons, and x-rays emitted from high-intensity laser interactions (1018−20 W/cm2) with structured silicon micro-wires on the surface of a 1 mm gold converter target using a 10 ps laser pulse. A total of four different wire configurations are tested, where the gaps (7–28 μm) between the wires and the thicknesses (3–6 μm) of the wires are varied, while the height remains constant (∼ 25 μm). We observe the largest enhancement in electrons, positrons, and x-rays with the sparsest wire configurations. The electron temperature (T e≈ 6 MeV) remains consistent across all shots, regardless of whether wires or planar targets are used. This suggests that the observed enhancement is due to increased laser light absorption by the accelerated electrons over a long scale length. Two-dimensional particle-in-cell simulations confirm that absorption is significantly enhanced with the wire target. Additionally, specific simulations examining laser pointing on different parts of the wire structure reveal that, while the final electron spectrum remains largely insensitive, the angular distribution is highly sensitive to these variations.