The measurement of early time laser beam reflection inside a cylindrical hohlraum on the National Ignition Facility

ORAL

Abstract

In a NIF cylindrical hohlraum, any specular reflection off the wall from the outer cone (incident angle of 50° and 45° relative to the wall) laser beams glints onto the capsule. If the glint power is sufficiently large during the picket (early time) of the laser pulse, it may seed high-mode perturbations that can grow during the implosion. To quantify the "glint" power on the capsule during the picket by the outer beams, we performed dedicated experiments on NIF using a witness foil as a surrogate for the capsule in a half-hohlraum target. The glint light intensity is measured via the time-resolved K-shell emission of the irradiated witness plate which is benchmarked to an external reference foil of the same material irradiated with two known laser powers. Measured glint power is lower than predicted by the model using low electron conduction flux limiters (f = 0.03). Detailed results of the measurement and its implications to the ICF experiments will be presented.

*This work was performed under the auspices of the U.S. Department of Energy by LLNS, LLC, under Contract No. DE-AC52- 07NA27344.

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Presenters

  • Hui Chen

    • Lawrence Livermore National Laboratory
    • LLNL

Authors

  • Hui Chen

    • Lawrence Livermore National Laboratory
    • LLNL

  • Tod Woods

    • Lawrence Livermore National Laboratory
    • Lawrence Livermore Natl Lab

  • Nuno Lemos

    • Lawrence Livermore Natl Lab
    • LLNL
    • Lawrence Livermore National Laboratory

  • Marilyn B Schneider

    • Lawrence Livermore Natl Lab
    • LLNL

  • Mordecai D Rosen

    • Lawrence Livermore Natl Lab
    • Lawrence Livermore National Laboratory

  • Joe Holder

    • Lawrence Livermore National Laboratory
    • Lawrence Livermore Natl Lab

  • Nobuhiko Izumi

    • Lawrence Livermore Natl Lab

  • Michael S Rubery

    • Lawrence Livermore Natl Lab
    • LLNL
    • Lawrence Livermore National Laboratory

  • Steven S Ross

    • Lawrence Livermore Natl Lab
    • Lawrence Livermore National Laboratory

  • Denise E Hinkel

    • LLNL
    • Lawrence Livermore National Laboratory
    • Lawrence Livermore Natl Lab

  • John D Moody

    • Lawrence Livermore National Laboratory
    • Lawrence Livermore Natl Lab

  • Otto L Landen

    • Lawrence Livermore Natl Lab

  • Katya Newman

    • Lawrence Livermore National Laboratory
    • Lawrence Livermore Natl Lab

  • Jared C Delora-Ellefson

    • Lawrence Livermore Natl Lab

  • Carl M Hardy

    • Lawrence Livermore Natl Lab

  • Nick Hash

    • Lawrence Livermore Natl Lab

  • Nathan Masters

    • Lawrence Livermore Natl Lab

  • Weston Montgomery

    • Lawrence Livermore Natl Lab
    • Lawrence Livermore National Laboratory
    • LLNL

  • Tom Zobrist

    • Lawrence Livermore Natl Lab