First early time symmetry and hot electron measurements for indirect drive ignition implosions on the National Ignition Facility

In ignition experiments on the National Ignition Facility (NIF), the symmetry of the hohlraum radiation drive for the first 2 ns is tuned using the re-emit technique [1]. At the same time, in order to maintain the capsule fuel on a low adiabat for successful ignition, the level of early $>$ 170 keV hot electrons generated in the hohlraum that reach the DT fuel [2] has to be $<$ few Joules. The generated hot electrons are inferred from the hohlraum hard x-ray (20-500 keV) spectra measured with the FFLEX diagnostic [3]. We report on the first re-emit symmetry experiments performed on NIF in full ignition scale hohlraums. We also infer the level of hot electrons intercepted by the capsule from $>$30 keV x-ray imaging of the re-emit sphere and hohlraum bremsstrahlung onto image plates whose data is normalized to the FFLEX spectra. [1] E.L. Dewald, \textit{et. al.,} Rev. Sci. Instrum. 79, 10E903 (2008). [2] E.L. Dewald \textit{et. al}., \textit{J. Phys.:Proceedings IFSA 2009}.