MEASUREMENTS OF EARLY TIME RADIATION ASYMMETRY IN VACUUM AND METHANE-FILLED HOHLRAUMS WITH THE REEMISSION BALL TECHNIQUE

In a previous paper [Phys. Rev. E 53, 5240 (1996)], we presented exper imental results of a technique for measuring time resolved symmetry in vacuum Hohlraums irradiated with the laser beams from the NOVA laser located at Lawrence Livermore National Laboratory. The experimental me thod involved x-ray imaging a high-Z ball placed in the center of a la ser irradiated vacuum Hohlraum. The signal from the high-Z ball was me asured along the Hohlraum axis, and compared with calculations. In thi s paper, using this experimental technique, we present time-dependent reemission measurements and calculations of the drive symmetry in vacu um and methane-filled Hohlraums for a shaped laser pulse. We also pres ent a method for determining the time dependence of the radiation flux from the measured reemission signal ratios, and do a modal analysis t o determine the values of the dominant Legendre components.