Direct Measurement of X-Ray Drive from Surrogate Targets in Nova Hohlraums

A new method for measuring x-ray drive in Nova hohlraums near target center using surrogate targets is proposed as an alternative to conventional wall-based techniques. A solid, low-density ( $0.3\mathrm{g}/{\mathrm{cm}}^3$) Si${\mathrm{O}}_2$ aerogel ball placed at the center of a Nova hohlraum is used to infer x-ray drive from the backlighter-imaged ablatively driven shock trajectory. A nearly 10% (40%) increase in peak radiation temperature (flux) near the hohlraum center in the presence of axial shields is predicted from radiation-hydrodynamics simulations and corroborated by experiment.