Effects of Self-Generated Magnetic Fields in Rayleigh--Taylor Unstable Laser-Irradiated Plastic Foils

Self-generated magnetic fields during the nonlinear Rayleigh--Taylor (RT) growth in laser-driven plastic foils are studied using 2-D magnetohydrodynamic simulations. The simulations show that at intensities of $\sim 6 \times 10^{14}$ W/cm$^{2}$, the dynamics of the fields sourced by the Biermann battery effect ($\sim \nabla T_{\mbox{e}} \times \nabla n_{\mbox{e}}$) are strongly affected by the Nernst convection, which compresses the fields toward the ablation surface. As a result, the fields are localized in areas of high resistivity and related magnetic dissipations limit the field growth, determining the magnitude of the fields. The fields saturate at about 2 to 3 MG for perturbation wavelengths $L > 100$ $\mu$m and at less than 0.1 MG for $L < 10$ $\mu$m because of increased magnetic dissipations at small spatial scales. Self-generated fields can moderately affect the nonlinear RT growth by redistributing heat fluxes for perturbations with $L > 100$ $\mu$m. The simulations show good agreement with measurements of magnetic fields in recent direct-drive planar experiments on the OMEGA EP laser.\footnote{L. Gao \textit{et al.}, Phys. Rev. Lett. \textbf{109}, 115001 (2012). } This material is based upon work supported by the Department of Energy National Nuclear Security Administration under Award Number DE-NA0001944.