Planar-Foil Laser-Imprint Experiments at the National Ignition Facility

Control of shell nonuniformities imprinted by the laser and amplified by hydrodynamic instabilities in the imploding target is critical for the success of direct-drive ignition at the National Ignition Faciliy (NIF). To study laser imprinting, we performed experiments that employed flat and corrugated planar CH foils driven with a single NIF beam. Face-on x-ray radiography was used to measure optical depth variations from which the amplitudes of the foil areal-density modulations were obtained. Simultaneous side-on radiography was used to measure the shell trajectory. Results of 3-D radiation-hydrodynamic code HYDRA [1] simulations of growth of imprint-seeded and surface-imposed perturbations as well as the shell trajectory are presented and compared with the experimental data. This material is based upon work supported by the Department of Energy National Nuclear Security Administration under Award Number DE-NA0003856 and under the auspices of the Lawrence Livermore National Security, LLC, (LLNS) under Contract No. DE-AC52-07NA27344

 

[1] M. M. Marinak et al., Phys. Plasmas 8, 2275 (2001).