Hohlraum Energetics with Elliptical Phase Plates on OMEGA

A set of 40 elliptical phase plates (E-IDI-300) was produced for hohlraum experiments on OMEGA to increase the coupling of laser energy to x-ray drive by reducing laser scattering losses from stimulated Brillouin and Raman scattering. A series of experiments were conducted with vacuum, gas-filled, and glass-lined Au hohlraums having a single laser entrance hole (``halfraums'') to quantify the effects of E-IDI-300 drive on the radiation temperature $T_{r}$ and the scattering losses. A $\sim $17-eV increase in $T_{r}$ was observed for the gas-filled targets driven with a shaped laser pulse (PS26). Gated ($\sim $80-ps) hard x{\-}ray ($>$8-keV) images of the thin-walled (5-\textit{$\mu $}m) hohlraums are used to illustrate the radiation hydrodynamics. The experimental results will be presented and compared to \textit{LASNEX} simulations. Measured characteristics of the single-beam, E-IDI-300 far-field intensity distribution will also be presented. This work was supported by the U.S. Department of Energy Office of Inertial Confinement Fusion under Cooperative Agreement No. DE-FC52-92SF19460.