Demonstration of Ion Kinetic Effects in Inertial Confinement Fusion Implosions and Investigation of Magnetic Reconnection Using Laser-Produced Plasmas

Shock-driven laser inertial confinement fusion (ICF) implosions have demonstrated the presence of ion kinetic effects in ICF implosions and also have been used as a proton source to probe the strongly driven reconnection of MG magnetic fields in laser-generated plasmas. Ion kinetic effects arise during the shock-convergence phase of ICF implosions when the mean free path for ion--ion collisions $\left( {\lambda_{\mbox{ii}} } \right)$ approaches the size of the hot-fuel region $\left( {R_{\mbox{fuel}} } \right)$ and may impact hot-spot formation and the possibility of ignition. To isolate and study ion kinetic effects, the ratio of $N_{\mbox{K}} ={\lambda_{\mbox{ii}} } \mathord{\left/ {\vphantom {{\lambda_{\mbox{ii}} } {R_{\mbox{fuel}} }}} \right. \kern-\nulldelimiterspace} {R_{\mbox{fuel}} }$ was varied in D$^{\mathrm{3}}$He-filled, shock-driven implosions at the Omega Laser Facility and the National Ignition Facility, from hydrodynamic-like conditions $\left( {N_{\mbox{K}} {\kern 1pt}\sim 0.01} \right)$ to strongly kinetic conditions $\left( {N_{\mbox{K}} \sim 10} \right).$ A strong trend of decreasing fusion yields relative to the predictions of hydrodynamic models is observed as $N_{\mathrm{K}}$ increases from $\sim 0.1$ to 10. Hydrodynamics simulations that include basic models of the kinetic effects that are likely to be present in these experiments---namely, ion diffusion and Knudsen-layer reduction of the fusion reactivity---are better able to capture the experimental results. This type of implosion has also been used as a source of monoenergetic 15-MeV protons to image magnetic fields driven to reconnect in laser-produced plasmas at conditions similar to those encountered at the Earth's magnetopause. These experiments demonstrate that for both symmetric and asymmetric magnetic-reconnection configurations, when plasma flows are much stronger than the nominal Alfv\'{e}n speed, the rate of magnetic-flux annihilation is determined by the flow velocity and is largely insensitive to initial plasma conditions. This work was supported by the Department of Energy Grant Number DE{\-}NA0001857.