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Time-resolved measurement of the x-ray continuum spectra of an inertial confinement fusion implosion

ORAL

Abstract

We report a time-resolved measurement of the x-ray continuum spectra of an indirect-drive inertial confinement fusion implosion using a tritium-deuterium-hydrogen mix as the fuel. The spectra in the energy range of 23-28 keV were measured using a new version of a conical graphite crystal spectrometer [1,2] coupled with a specialized x-ray streak camera [3,4]. The time history of the logarithmic slope of the spectra representing the electron temperature of the hot spot was extracted using forward fitting of the time-energy binned streak camera signal to the expected Maxwellian spectral shape. The measurement uncertainties were obtained using a recently developed Monte-Carlo technique [5]. The time-resolved (30 ps time bins) electron temperature was found to vary within the duration of the hot-spot x-ray emission (~120 ps FWHM), rising from ~ 3keV up to 5.2 keV at peak emission and then slightly decreasing to ~4.5 keV. While the obtained ~12% r.m.s. uncertainties on the electron temperature prevent more detailed interpretation of the temperature’s time-history, this can be substantially improved (down to ~4% r.m.s) by reducing x-ray attenuation in the spectrometer. On a follow up implosion this would lead to more optimized x-ray detection by the streak camera.

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Publication: [1] D.B. Thorn et al., "On the Design of the NIF Continuum Spectrometer", Proc. Of SPIE, 10390, 1039009-1 (2017)<br>[2] M.J. MacDonald et al., "Absolute calibration of the continuum x-ray spectrometer (ConSpec) at the National Ignition Facility", J. Instrum. 14, P12009 (2019)<br>[3] A. G. MacPhee et al., "Improving the off-axis spatial resolution and dynamic range of the NIF X-ray streak cameras", Rev. Sci. Instrum. 87, 11E202 (2016)<br>[4] A. G. MacPhee et al., "Performance of a hardened x-ray streak camera at LLNL's National Ignition Facility", (submitted for publication) (2022)<br>[5] S. Stoupin et al., "A Monte Carlo technique to model performance of streak-camera-based time-resolving x-ray spectrometers", (submitted for publication) (2022)

Presenters

  • Stanislav Stoupin

    Lawrence Livermore National Laboratory, LLNL

Authors

  • Stanislav Stoupin

    Lawrence Livermore National Laboratory, LLNL

  • Andrew G MacPhee

    LLNL, Lawrence Livermore Natl Lab

  • Dave J Schlossberg

    Lawrence Livermore National Laboratory, Lawrence Livermore Natl Lab

  • Neil Ose

    Lawrence Livermore National Laboratory, Lawrence Livermore Natl Lab

  • Michael J MacDonald

    Lawrence Livermore National Laboratory, Lawrence Livermore Natl Lab, LLNL

  • Dean R Rusby

    Lawrence Livermore National Lab, LLNL

  • Marilyn B Schneider

    Lawrence Livermore Natl Lab, LLNL