Laser Propagation Effects and Symmetry at Hohlraum Temperatures of Order 100eV

Radiation emission experiments from capsules in NIF-0.7 scale vacuum hohlraums at the Omega laser frequently indicate shapes that are more oblate (with respect to the hohlraum symmetry axis) than simulations.\footnote{G. Kyrala et al., BAPS \textbf{52} (16), p. 318 (2007) } This has been attributed to the modeling of laser beams which make relatively small (21\r{ }) angles with that axis. Shape agreement is significantly improved by assuming that the laser beams are statistically scattered through a parametrically controlled algorithm. We have examined the simulations with the LIP post-processor\footnote{ICF Annual Report, LLNL, UCRL-LR-105820-98, p. 13 (1998) } to see whether laser plasma instabilities could account for the scattering. Due to the low laser intensities, instabilities are relatively weak and appear to be confined to regions close the initial capsule and hohlraum wall boundaries; nevertheless the pF3D code\footnote{S.H. Glenzer et al., Nature Physics \textbf{3}, 716 (2007)} should be useful in evaluating their role in laser propagation modification. In addition, we have estimated the effect of the experimental phase plate speckle patterns on stable beam scattering.