Proton radiography of a highly asymmetric laser-driven magnetic reconnection geometry

In experiments performed at the OMEGA EP laser facility at the Laboratory for Laser Energetics, the typical laser-driven magnetic reconnection geometry was adapted such that one high intensity pulse (I ≈ 10¹⁹ Wcm^-2) was focused alongside a moderate intensity UV long pulse (I ≈ 10¹⁴ Wcm^-2) on foil targets. First, the long pulse ablates a region of the target and misaligned temperature and density gradients in the plasma plume generate an azimuthal magnetic field via the Biermann battery mechanism. After the Biermann field develops, the high intensity pulse arrives on target and produces a relativistic, highly magnetized plasma (σ = B²/μ₀n_em_ec² ≥ 1) which sweeps across the target surface with velocities near the speed of light. Proton radiography captures the evolution of the strong, impulsive magnetic field generated by the high intensity pulse and its interaction with the relatively slowly evolving Biermann battery fields. Quantitative measurements of the magnetic field dynamics will be presented, as well as 2D and 3D particle-in-cell simulation results.