Role of Hydrodynamics Simulations for Laser-Plasma Interaction Predictive Capability

Efforts to predict and control laser-plasma interactions (LPI) in ignition hohlraum targets for the National Ignition Facility [G. H. Miller et al., Optical Eng. 43, 2841 (2004)] are based on plasma conditions provided by radiation hydrodynamic simulations. Recent experiments provide compelling evidence that codes such as hydra [M. M. Marinak et al., Phys. Plasmas 8, 2275 (2001)] can accurately predict the plasma conditions in laser heated targets such as gas-filled balloon (gasbag) and hohlraum platforms for studying LPI. Initially puzzling experimental observations are found to be caused by bulk hydrodynamic phenomena. Features in backscatter spectra and transmitted light spectra are reproduced from the simulated plasma conditions. Simulations also agree well with Thomson scattering measurements of the electron temperature. The calculated plasma conditions are used to explore a linear-gain based phenomenological model of backscatter. For long plasmas at ignition-relevant electron temperatures, the measured backscatter increases monotonically with gain and is consistent with linear growth for low reflectivities. These results suggest a role for linear gain postprocessing as a metric for assessing LPI risk.

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