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Title: Simultaneous diagnosis of radial profiles and mix in NIF ignition-scale implosions via X-ray spectroscopy

Abstract

In a National Ignition Facility implosion, hydrodynamic instabilities may cause the cold material from the imploding shell to be injected into the hot-spot (hot-spot mix), enhancing the radiative and conductive losses, which in turn may lead to a quenching of the ignition process. The bound-bound features of the spectrum emitted by high-Z ablator dopants that get mixed into the hot-spot have been previously used to infer the total amount of mixed mass; however, the typical errorbars are larger than the maximum tolerable mix. We present in this paper an improved 2D model for mix spectroscopy which can be used to retrieve information on both the amount of mixed mass and the full imploded plasma profile. By performing radiation transfer and simultaneously fitting all of the features exhibited by the spectra, we are able to constrain self-consistently the effect of the opacity of the external layers of the target on the emission, thus improving the accuracy of the inferred mixed mass. The model's predictive capabilities are first validated by fitting simulated spectra arising from fully characterized hydrodynamic simulations, and then, the model is applied to previously published experimental results, providing values of mix mass in agreement with previous estimates. Finally, wemore » show that the new self consistent procedure leads to better constrained estimates of mix and also provides insight into the sensitivity of the hot-spot spectroscopy to the spatial properties of the imploded capsule, such as the in-flight aspect ratio of the cold fuel surrounding the hotspot.« less

Authors:
 [1];  [2];  [3];  [2]; ORCiD logo [4];  [1];  [4];  [1]; ORCiD logo [3];  [1]
  1. Univ. of Oxford (United Kingdom). Dept. of Physics. Clarendon Lab.
  2. Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
  3. Univ. of York (United Kingdom). Dept. of Physics
  4. Univ. of Rochester, NY (United States). Lab. for Laser Energetics
Publication Date:
Research Org.:
Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Univ. of Rochester, NY (United States); Univ. of Oxford (United Kingdom); Univ. of York (United Kingdom)
Sponsoring Org.:
USDOE National Nuclear Security Administration (NNSA); New York State Energy Research and Development Authority (NYSERDA) (United States); Engineering and Physical Sciences Research Council (EPSRC); Royal Society (United Kingdom)
OSTI Identifier:
1438689
Alternate Identifier(s):
OSTI ID: 1407434
Report Number(s):
LLNL-JRNL-736521
Journal ID: ISSN 1070-664X; TRN: US1900487
Grant/Contract Number:  
AC52-07NA27344; NA0001944; EP/L000849/1; EP/L000644/1; EP/H035877/1
Resource Type:
Accepted Manuscript
Journal Name:
Physics of Plasmas
Additional Journal Information:
Journal Volume: 24; Journal Issue: 11; Journal ID: ISSN 1070-664X
Publisher:
American Institute of Physics (AIP)
Country of Publication:
United States
Language:
English
Subject:
70 PLASMA PHYSICS AND FUSION TECHNOLOGY; doping; atmospheric radiation; x-ray spectroscopy; radiography; hydrodynamics; tectonophysics; electronic structure; emission spectra

Citation Formats

Ciricosta, O., Scott, H., Durey, P., Hammel, B. A., Epstein, R., Preston, T. R., Regan, S. P., Vinko, S. M., Woolsey, N. C., and Wark, J. S. Simultaneous diagnosis of radial profiles and mix in NIF ignition-scale implosions via X-ray spectroscopy. United States: N. p., 2017. Web. doi:10.1063/1.5000774.
Ciricosta, O., Scott, H., Durey, P., Hammel, B. A., Epstein, R., Preston, T. R., Regan, S. P., Vinko, S. M., Woolsey, N. C., & Wark, J. S. Simultaneous diagnosis of radial profiles and mix in NIF ignition-scale implosions via X-ray spectroscopy. United States. doi:10.1063/1.5000774.
Ciricosta, O., Scott, H., Durey, P., Hammel, B. A., Epstein, R., Preston, T. R., Regan, S. P., Vinko, S. M., Woolsey, N. C., and Wark, J. S. Mon . "Simultaneous diagnosis of radial profiles and mix in NIF ignition-scale implosions via X-ray spectroscopy". United States. doi:10.1063/1.5000774. https://www.osti.gov/servlets/purl/1438689.
@article{osti_1438689,
title = {Simultaneous diagnosis of radial profiles and mix in NIF ignition-scale implosions via X-ray spectroscopy},
author = {Ciricosta, O. and Scott, H. and Durey, P. and Hammel, B. A. and Epstein, R. and Preston, T. R. and Regan, S. P. and Vinko, S. M. and Woolsey, N. C. and Wark, J. S.},
abstractNote = {In a National Ignition Facility implosion, hydrodynamic instabilities may cause the cold material from the imploding shell to be injected into the hot-spot (hot-spot mix), enhancing the radiative and conductive losses, which in turn may lead to a quenching of the ignition process. The bound-bound features of the spectrum emitted by high-Z ablator dopants that get mixed into the hot-spot have been previously used to infer the total amount of mixed mass; however, the typical errorbars are larger than the maximum tolerable mix. We present in this paper an improved 2D model for mix spectroscopy which can be used to retrieve information on both the amount of mixed mass and the full imploded plasma profile. By performing radiation transfer and simultaneously fitting all of the features exhibited by the spectra, we are able to constrain self-consistently the effect of the opacity of the external layers of the target on the emission, thus improving the accuracy of the inferred mixed mass. The model's predictive capabilities are first validated by fitting simulated spectra arising from fully characterized hydrodynamic simulations, and then, the model is applied to previously published experimental results, providing values of mix mass in agreement with previous estimates. Finally, we show that the new self consistent procedure leads to better constrained estimates of mix and also provides insight into the sensitivity of the hot-spot spectroscopy to the spatial properties of the imploded capsule, such as the in-flight aspect ratio of the cold fuel surrounding the hotspot.},
doi = {10.1063/1.5000774},
journal = {Physics of Plasmas},
number = 11,
volume = 24,
place = {United States},
year = {2017},
month = {11}
}

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Figures / Tables:

FIG. 1 FIG. 1: Schematic diagram of the target geometry used to model the mix spectra. The radii of the different layers in each simulation are constrained by the ion densities (used as fit parameters) and by the known amount of each material (by experimental design). Radiation transfer is performed through themore » different layers, and then a set of rays parallel to the equator (i.e. perpendicular to the mix jet) is used to compute the emitted spectral intensity seen by an equatorial spectrometer. The predicted signal is calculated assuming constant conditions through the X-ray burnwidth time (125 ps).« less

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    Figures/Tables have been extracted from DOE-funded journal article accepted manuscripts.