Self-generated magnetic fields in direct-drive implosion experiments

Electric and self-generated magnetic fields in direct-drive implosion experiments on the OMEGA Laser Facility were investigated employing radiography with similar to 10- to 60-MeV protons. The experiment used plastic-shell targets with imposed surface defects (glue spots, wires, and mount stalks), which enhance self-generated fields. The fields were measured during the 1-ns laser drive with an on-target intensity similar to 10(15) W/cm(2). Proton radiographs show multiple ring-like structures produced by electric fields similar to 10(7) V/cm and fine structures from surface defects, indicating self-generated fields up to similar to 3 MG. These electric and magnetic fields show good agreement with two-dimensional magnetohydrodynamic simulations when the latter include the del T-e x del n(e) source, Nernst convection, and anisotropic resistivity. The simulations predict that self-generated fields affect heat fluxes in the conduction zone and, through this, affect the growth of local perturbations. (C) 2014 AIP Publishing LLC.