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Title: X-ray scattering measurements on imploding CH spheres at the National Ignition Facility

Abstract

In this study, we have performed spectrally resolved x-ray scattering measurements on highly compressed polystyrene at pressures of several tens of TPa (100 Mbar) created by spherically convergent shocks at the National Ignition Facility. Scattering data of line radiation at 9.0 keV were recorded from the dense plasma shortly after shock coalescence. Accounting for spatial gradients, opacity effects, and source broadening, we demonstrate the sensitivity of the elastic scattering component to carbon K -shell ionization while at the same time constraining the temperature of the dense plasma. Finally, for six times compressed polystyrene, we find an average temperature of 86 eV and carbon ionization state of 4.9, indicating that widely used ionization models need revision in order to be suitable for the extreme states of matter tested in our experiment.

Authors:
 [1];  [2];  [3];  [4];  [3];  [3];  [5];  [6];  [3];  [3];  [3];  [3];  [3];  [3];  [7];  [1];  [4];  [3]
  1. Univ. of California, Berkeley, CA (United States). Department of Physics
  2. University of Warwick (United Kingdom). Centre for Fusion, Space and Astrophysics, Department of Physics; AWE plc (United Kingdom). Plasma Physics Group, Radiation Physics Department
  3. Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
  4. University of Warwick (United Kingdom). Centre for Fusion, Space and Astrophysics, Department of Physics
  5. SLAC National Accelerator Lab., Menlo Park, CA (United States)
  6. Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Washington State Univ., Pullman, WA (United States). Institute for Shock Physics
  7. GSI Helmholtzzentrum fur Schwerionenforschung (Germany)
Publication Date:
Research Org.:
Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
Sponsoring Org.:
USDOE National Nuclear Security Administration (NNSA); USDOE Office of Science (SC), Fusion Energy Sciences (FES) (SC-24)
OSTI Identifier:
1393340
Alternate Identifier(s):
OSTI ID: 1267540
Report Number(s):
LLNL-JRNL-704306
Journal ID: ISSN 2470-0045; PLEEE8
Grant/Contract Number:
AC52-07NA27344; FG52-10NA29649; NA0001859; 13-ERD-073
Resource Type:
Journal Article: Accepted Manuscript
Journal Name:
Physical Review E
Additional Journal Information:
Journal Volume: 94; Journal Issue: 1; Journal ID: ISSN 2470-0045
Publisher:
American Physical Society (APS)
Country of Publication:
United States
Language:
English
Subject:
70 PLASMA PHYSICS AND FUSION TECHNOLOGY

Citation Formats

Kraus, D., Chapman, D. A., Kritcher, A. L., Baggott, R. A., Bachmann, B., Collins, G. W., Glenzer, S. H., Hawreliak, J. A., Kalantar, D. H., Landen, O. L., Ma, T., Le Pape, S., Nilsen, J., Swift, D. C., Neumayer, P., Falcone, R. W., Gericke, D. O., and Döppner, T. X-ray scattering measurements on imploding CH spheres at the National Ignition Facility. United States: N. p., 2016. Web. doi:10.1103/PhysRevE.94.011202.
Kraus, D., Chapman, D. A., Kritcher, A. L., Baggott, R. A., Bachmann, B., Collins, G. W., Glenzer, S. H., Hawreliak, J. A., Kalantar, D. H., Landen, O. L., Ma, T., Le Pape, S., Nilsen, J., Swift, D. C., Neumayer, P., Falcone, R. W., Gericke, D. O., & Döppner, T. X-ray scattering measurements on imploding CH spheres at the National Ignition Facility. United States. doi:10.1103/PhysRevE.94.011202.
Kraus, D., Chapman, D. A., Kritcher, A. L., Baggott, R. A., Bachmann, B., Collins, G. W., Glenzer, S. H., Hawreliak, J. A., Kalantar, D. H., Landen, O. L., Ma, T., Le Pape, S., Nilsen, J., Swift, D. C., Neumayer, P., Falcone, R. W., Gericke, D. O., and Döppner, T. Thu . "X-ray scattering measurements on imploding CH spheres at the National Ignition Facility". United States. doi:10.1103/PhysRevE.94.011202. https://www.osti.gov/servlets/purl/1393340.
@article{osti_1393340,
title = {X-ray scattering measurements on imploding CH spheres at the National Ignition Facility},
author = {Kraus, D. and Chapman, D. A. and Kritcher, A. L. and Baggott, R. A. and Bachmann, B. and Collins, G. W. and Glenzer, S. H. and Hawreliak, J. A. and Kalantar, D. H. and Landen, O. L. and Ma, T. and Le Pape, S. and Nilsen, J. and Swift, D. C. and Neumayer, P. and Falcone, R. W. and Gericke, D. O. and Döppner, T.},
abstractNote = {In this study, we have performed spectrally resolved x-ray scattering measurements on highly compressed polystyrene at pressures of several tens of TPa (100 Mbar) created by spherically convergent shocks at the National Ignition Facility. Scattering data of line radiation at 9.0 keV were recorded from the dense plasma shortly after shock coalescence. Accounting for spatial gradients, opacity effects, and source broadening, we demonstrate the sensitivity of the elastic scattering component to carbon K -shell ionization while at the same time constraining the temperature of the dense plasma. Finally, for six times compressed polystyrene, we find an average temperature of 86 eV and carbon ionization state of 4.9, indicating that widely used ionization models need revision in order to be suitable for the extreme states of matter tested in our experiment.},
doi = {10.1103/PhysRevE.94.011202},
journal = {Physical Review E},
number = 1,
volume = 94,
place = {United States},
year = {Thu Jul 21 00:00:00 EDT 2016},
month = {Thu Jul 21 00:00:00 EDT 2016}
}

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  • The first 96 and 192 beam vacuum hohlraum have been fielded at the National Ignition Facility demonstrating radiation temperatures up to 340 eV and fluxes of 20 TW/sr representing a 20 times flux increase over NOVA/Omega scale hohlraums. The vacuum hohlraums were irradiated with 2 ns square pulses with energies between 150 - 635 kJ. They produced nearly Planckian spectra with about 30 {+-} 10% more flux than predicted by the current radiation hydrodynamic simulations after careful verification of all component calibrations (which included an {approx} 10% downward correction to Center X-Ray Optics opacities just below the Cu L edgemore » at 50-750 eV), cable deconvolution, and analysis software routines. To corroborate these results, first a half hohlraum experiment was conducted using a single 2 ns-long axial quad with an irradiance of {approx} 1-2 x 10{sup 15} W/cm{sup 2} for comparison with NIF Early Light experiments completed in 2004. Second, we completed a conversion efficiency test using a 128-beam nearly uniformly illuminated gold sphere with intensities kept low (at 1 x 10{sup 14} W/cm{sup 2} over 5 ns) to avoid sensitivity to modeling uncertainties for non-local heat conduction and non-linear absorption mechanisms, to compare with similar intensity, 3 ns OMEGA sphere results. The 2004 and 2009 NIF half-hohlraums agreed to 10% in flux, but more importantly, the 2006 OMEGA Au Sphere, the 2009 NIF Au sphere and the calculated Au conversion efficiency agree to {+-}5% in flux, which is estimated to be the absolute calibration accuracy of the DANTEs. Hence we concluded the 30 {+-} 10% higher than expected radiation fluxes from the 96 and 192 beam vacuum hohlraums are attributable to differences in physics when we transitioned to large hot hohlraums. Specifically, using variants in the atomic physics models and electron heat conduction, newer simulations show that nonlocalization of energy deposition leads to less energy being stored in the coronal plasma leading to higher x-ray conversion efficiency. Since the larger volume-to-area ratio hohlraums have large coronal plasmas which scale volumetrically, the reduction in energy losses to the corona become more pronounced than for smaller NOVA/Omega scale hohlraums. The higher conversion efficiencies are also consistent with observations from other 1 ns gold sphere experiments conducted at Omega with 1 x 10{sup 15} W/cm{sup 2} laser irradiances.« less
  • The first 96 and 192 beam vacuum Hohlraum target experiments have been fielded at the National Ignition Facility demonstrating radiation temperatures up to 340 eV and fluxes of 20 TW/sr as viewed by DANTE representing an {approx}20 times flux increase over NOVA/Omega scale Hohlraums. The vacuum Hohlraums were irradiated with 2 ns square laser pulses with energies between 150 and 635 kJ. They produced nearly Planckian spectra with about 30{+-}10% more flux than predicted by the preshot radiation hydrodynamic simulations. To validate these results, careful verification of all component calibrations, cable deconvolution, and software analysis routines has been conducted. Inmore » addition, a half Hohlraum experiment was conducted using a single 2 ns long axial quad with an irradiance of {approx}2x10{sup 15} W/cm{sup 2} for comparison with NIF Early Light experiments completed in 2004. We have also completed a conversion efficiency test using a 128-beam nearly uniformly illuminated gold sphere with intensities kept low (at 1x10{sup 14} W/cm{sup 2} over 5 ns) to avoid sensitivity to modeling uncertainties for nonlocal heat conduction and nonlinear absorption mechanisms, to compare with similar intensity, 3 ns OMEGA sphere results. The 2004 and 2009 NIF half-Hohlraums agreed to 10% in flux, but more importantly, the 2006 OMEGA Au Sphere, the 2009 NIF Au sphere, and the calculated Au conversion efficiency agree to {+-}5% in flux, which is estimated to be the absolute calibration accuracy of the DANTEs. Hence we conclude that the 30{+-}10% higher than expected radiation fluxes from the 96 and 192 beam vacuum Hohlraums are attributable to differences in physics of the larger Hohlraums.« less
  • Here, indirect drive experiments at the National Ignition Facility are designed to achieve fusion by imploding a fuel capsule with x rays from a laser-driven hohlraum. Previous experiments have been unable to determine whether a deficit in measured ablator implosion velocity relative to simulations is due to inadequate models of the hohlraum or ablator physics. ViewFactor experiments allow for the first time a direct measure of the x-ray drive from the capsule point of view. The experiments show a 15%–25% deficit relative to simulations and thus explain nearly all of the disagreement with the velocity data. In addition, the datamore » from this open geometry provide much greater constraints on a predictive model of laser-driven hohlraum performance than the nominal ignition target.« less