Magnetic Reconnection in Highly-Extended Current Sheets at the NIF

We present results from experiments at the National Ignition Facility to study reconnection in large and highly-extended current sheets. Two highly-elongated plasma plumes were produced by tiling two rows of lasers, with magnetic fields generated in each plume by the Biermann battery effect. X-ray measurements provided estimates of local electron temperature and density scale length, which were also used to benchmark simulations. Detailed magnetic field observations, obtained from proton radiography using a DHe3 capsule implosion, reveal reconnection occurring in an extended, quasi-1D current sheet with large aspect ratio $\sim$100. The 1-D geometry allowed a rigorous and unique reconstruction of the magnetic field, which showed a reconnection current sheet that thinned down to a half-width close to the electron gyro-scale. Despite the large aspect ratio, a large fraction of the magnetic flux reconnected, suggesting fast reconnection supported by the non-gyrotropic electron pressure tensor.