Computer simulations of laser hot spots and implosion symmetry kiniform phase plate experiments on Nova

LASNEX computer code simulations have been performed for radiation symmetry experiments on the Nova laser with vacuum and gas-filled hohlraum targets [R. L. Kauffman , Phys. Plasmas 5, 1927 (1998)]. In previous experiments wi th unsmoothed laser beams, the symmetry was substantially shifted by deflec tion of the laser beams. In these experiments, laser beams have been smooth ed with Kiniform Phase Plates in an attempt to remove deflection of the bea ms. The experiments have shown that this smoothing significantly improves t he agreement with LASNEX calculations of implosion symmetry. The images of laser produced hot spots on the inside of the hohlraum case have been found to differ from LASNEX calculations, suggesting that some beam deflection o r self-focusing may still be present or that emission from interpenetrating plasmas is an important component of the images. The measured neutron yiel ds are in good agreement with simulations for vacuum hohlraums but are far different for gas-filled hohlraums. (C) 2000 American Institute of Physics. [S1070-664X(00)02505-2].