Anomalous Absorption by the Two-Plasmon-Decay Instability in Directly Driven Inertial Confinement Fusion Experiments

ORAL

Abstract

Simulations of directly driven inertial confinement fusion experiments on the OMEGA Laser System were significantly improved with the inclusion of an inline model for crossed-beam energy transfer along with a nonlocal model for heat transport. Absorption and shell-velocity time histories are accurately predicted when experiments are driven at relatively low overlapped laser intensity. Discrepancies appear at higher intensity, however, with higher-than-expected laser absorption on target. Strong correlation between those discrepancies and signatures of the two-plasmon-decay instability (TPDI)---including time-dependent half-harmonic emission and hard x-ray signals---indicate that TPDI is responsible for this anomalous absorption. The data suggest that up to $\sim30\%$ of the laser right reaching $n_c/4$ can be absorbed locally when the TPDI threshold is exceeded, which is consistent with LPSE simulations.

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Authors

  • David Turnbull

    Laboratory for Laser Energetics, LLE

  • A. V. Maximov

    Laboratory for Laser Energetics, University of Rochester, Laboratory for Laser Energetics, University of Rochester, University of Rochester, NY 14623, USA

  • Dana Edgell

    Laboratory for Laser Energetics, University of Rochester

  • Wolf Seka

    Laboratory for Laser Energetics, University of Rochester, Laboratory for Laser Energetics

  • Tim Collins

    LLE, University of Rochester, University of Rochester - LLE, Laboratory for Laser Energetics, University of Rochester, Laboratory for Laser Energetics

  • John Marozas

    Laboratory for Laser Energetics, U. of Rochester, LLE, University of Rochester, Laboratory for Laser Energetics, University of Rochester - LLE, University of Rochester, Laboratory for Laser Energetics

  • Russ Follett

    Laboratory for Laser Energetics, LLE

  • J.P. Palastro

    Laboratory for Laser Energetics, Laboratory for Laser Energetics, U. of Rochester, Laboratory for Laser Energetics, University of Rochester, University of Rochester, University of Rochester, Laboratory for Laser Energetics

  • D.H. Froula

    Laboratory for Laser Energetics, Laboratory for Laser Energetics, University of Rochester, University of Rochester, LLE rochester, University of Rochester, Laboratory for Laser Energetics