Revisiting hot electron generation in ignition-scale hohlraums

Recent work\footnote{H. F. Robey, \textit{et. al}., Phys. Plasmas 21, 022703 (2014)} invoking hot electron preheat in NIC ignition experiments is motivating a fresh look at hot electron generation in ignition-scale hohlraums. Various mechanisms for high energy electron generation are considered, with particular attention to their time dependence and the potential role of the two plasmon decay instability in the main laser pulse.\footnote{William L. Kruer, Nathan Meezan, S. P. Regan, \textit{et. al},, Journal of Physics Conference Series 244, 022020 (2010)} The energy at risk calculations\footnote{S. P. Regan, \textit{et. al},. Phys. Plasmas 17, 020703 (2010)} are updated to include the effects of cross beam energy transfer on the time-dependent energy and intensity of the inner beams as well as improvements in the calculated plasma conditions. The generation of hot electrons by the Raman-scattered light driving the two plasmon decay instability and the effect of the Weibel instability on the propagation of the hot electrons are also briefly considered. Uncertainties in interpreting the energy in hot electrons from hard x-ray measurements and techniques to reduce hot electron generation are discussed.