title: Mitigating laser imprint in direct-drive inertial confinement fusion implosions with high-Z dopants.
abstract: Nonuniformities seeded by both long- and short-wavelength laser perturbations can grow via Rayleigh-Taylor (RT) instability in direct-drive inertial confinement fusion, leading to performance reduction in low-adiabat implosions. To mitigate the effect of laser imprinting on target performance, spherical RT experiments have been performed on OMEGA using Si- or Ge-doped plastic targets in a cone-in-shell configuration. Compared to a pure plastic target, radiation preheating from these high-Z dopants (Si/Ge) increases the ablation velocity and the standoff distance between the ablation front and laser-deposition region, thereby reducing both the imprinting efficiency and the RT growth rate. Experiments showed a factor of 2-3 reduction in the laser-imprinting efficiency and a reduced RT growth rate, leading to significant (3-5 times) reduction in the σ(rms) of shell ρR modulation for Si- or Ge-doped targets. These features are reproduced by radiation-hydrodynamics simulations using the two-dimensional hydrocode DRACO.
authors.affiliation: Laboratory for Laser Energetics, University of Rochester, 250 East River Road, Rochester, New York 14623, USA. shu@lle.rochester.edu
authors.forename: S X
authors.initials: SX
authors.lastname: Hu
authors.forename: G
authors.initials: G
authors.lastname: Fiksel
authors.forename: V N
authors.initials: VN
authors.lastname: Goncharov
authors.forename: S
authors.initials: S
authors.lastname: Skupsky
authors.forename: D D
authors.initials: DD
authors.lastname: Meyerhofer
authors.forename: V A
authors.initials: VA
authors.lastname: Smalyuk