LLE Review 133

Review 133


This volume of the LLE Review, covering October–December 2012, features "A Polar-Drive Shock-Ignition Design for the National Ignition Facility," which reviews the performance of a shock-ignition polar-drive design that is estimated using 1-D and 2-D simulations for implementation on the National Ignition Facility. The authors quantify the impact of instabilities and uncertainties on gain to study the robustness of this approach in experimental conditions. The target is shown to robustly ignite when taking into account uncertainties in the shock timing and initial gas density and nonuniformities caused by the laser drive, capsule position, and asymmetries.

Additional highlights of research presented in this issue include the following:

  • Polar-drive experiments on OMEGA are simulated and a good agreement with DRACO simulations in terms of areal density and symmetry is observed. The scaling of these experiments to the National Ignition Facility and the role of laser–plasma interactions are discussed.
  • A comparison of measured and simulated angular dependence of the unabsorbed light in OMEGA experiments is presented. The 3-D simulations show that cross-beam energy transfer explains the decreased laser absorption, which can be mitigated using smaller laser beams on target and tuning the wavelength of the laser beams organized in different rings.
  • A model of two-plasmon decay based on a common electron plasma wave is described. This model is consistent with the threshold for hot-electron production measured in multibeam OMEGA and OMEGA EP experiments.
  • The physics and possible implementations of two-state optical zooming to mitigate cross-beam energy transfer on OMEGA are reviewed. Scattering of the incident laser energy is reduced using a smaller beam radius on target for the main drive while maintaining the beam size for the pickets.
  • A report on the reliability and accuracy improvement of streak-camera–based short-pulse measurements by homogenizing the slit illumination using an anamorphic diffuser and calibrating the space-charge broadening, for application to the measurement of OMEGA EP pulses with durations ranging from 8 to 250 ps is presented.
  • The design of a new solid-state, high-voltage pulse generator for driving large-aperture Pockels cells is presented. These generators are reliable replacements for the obsolete thyratron-based drivers used in the large-aperture ring amplifiers of the OMEGA and OMEGA EP front ends.

Table of Contents