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}.