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Title: The influence of hohlraum dynamics on implosion symmetry in indirect drive inertial confinement fusion experiments

Abstract

High laser energy (>1.2 MJ) implosion experiments on the National Ignition Facility show that low mode implosion symmetry is highly dependent on an expanding high-Z wall “bubble” plasma feature. The bubble is caused by the early time deposition of laser beams incident on the interior near the entrance of the cylindrical hohlraum (outer cone beams). It absorbs beams designated for the waist of the hohlraum (inner cone beams) causing a redistribution of x-ray flux on the capsule. From measurements, we are able to quantify the absorption and expansion of this bubble. Measurements show that the resulting hot spot is more oblate when there is more inner beam absorption in the bubble. We also find absorption in the bubble to be between 51 ± 3% and 62 ± 2%. This bubble absorption is found to evolve predictably as a function of the early time outer cone laser pulse fluence and the pulse length. From this, a phenomenological model of the effective drive symmetry and subsequent implosion shape is found indicating a very strong dependence of implosion shape on early time laser fluence and laser pulse duration.

Authors:
 [1]; ORCiD logo [1];  [1];  [1];  [1]; ORCiD logo [1];  [1];  [1];  [1]; ORCiD logo [1];  [1];  [1]; ORCiD logo [1];  [1]
  1. Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
Publication Date:
Research Org.:
Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
Sponsoring Org.:
USDOE National Nuclear Security Administration (NNSA)
OSTI Identifier:
1469454
Report Number(s):
LLNL-JRNL-738440
Journal ID: ISSN 1070-664X; 891669
Grant/Contract Number:  
AC52-07NA27344
Resource Type:
Journal Article: Accepted Manuscript
Journal Name:
Physics of Plasmas
Additional Journal Information:
Journal Volume: 25; Journal Issue: 8; 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; electron density; plasmas; x-rays; tectonophysics; speed of sound; transition metals; chemical elements; hydrodynamics simulations; radiograph; nuclear fusion

Citation Formats

Ralph, J. E., Landen, O., Divol, L., Pak, A., Ma, T., Callahan, D. A., Kritcher, A. L., Döppner, T., Hinkel, D. E., Jarrott, C., Moody, J. D., Pollock, B. B., Hurricane, O., and Edwards, M. J. The influence of hohlraum dynamics on implosion symmetry in indirect drive inertial confinement fusion experiments. United States: N. p., 2018. Web. doi:10.1063/1.5023008.
Ralph, J. E., Landen, O., Divol, L., Pak, A., Ma, T., Callahan, D. A., Kritcher, A. L., Döppner, T., Hinkel, D. E., Jarrott, C., Moody, J. D., Pollock, B. B., Hurricane, O., & Edwards, M. J. The influence of hohlraum dynamics on implosion symmetry in indirect drive inertial confinement fusion experiments. United States. doi:10.1063/1.5023008.
Ralph, J. E., Landen, O., Divol, L., Pak, A., Ma, T., Callahan, D. A., Kritcher, A. L., Döppner, T., Hinkel, D. E., Jarrott, C., Moody, J. D., Pollock, B. B., Hurricane, O., and Edwards, M. J. Mon . "The influence of hohlraum dynamics on implosion symmetry in indirect drive inertial confinement fusion experiments". United States. doi:10.1063/1.5023008. https://www.osti.gov/servlets/purl/1469454.
@article{osti_1469454,
title = {The influence of hohlraum dynamics on implosion symmetry in indirect drive inertial confinement fusion experiments},
author = {Ralph, J. E. and Landen, O. and Divol, L. and Pak, A. and Ma, T. and Callahan, D. A. and Kritcher, A. L. and Döppner, T. and Hinkel, D. E. and Jarrott, C. and Moody, J. D. and Pollock, B. B. and Hurricane, O. and Edwards, M. J.},
abstractNote = {High laser energy (>1.2 MJ) implosion experiments on the National Ignition Facility show that low mode implosion symmetry is highly dependent on an expanding high-Z wall “bubble” plasma feature. The bubble is caused by the early time deposition of laser beams incident on the interior near the entrance of the cylindrical hohlraum (outer cone beams). It absorbs beams designated for the waist of the hohlraum (inner cone beams) causing a redistribution of x-ray flux on the capsule. From measurements, we are able to quantify the absorption and expansion of this bubble. Measurements show that the resulting hot spot is more oblate when there is more inner beam absorption in the bubble. We also find absorption in the bubble to be between 51 ± 3% and 62 ± 2%. This bubble absorption is found to evolve predictably as a function of the early time outer cone laser pulse fluence and the pulse length. From this, a phenomenological model of the effective drive symmetry and subsequent implosion shape is found indicating a very strong dependence of implosion shape on early time laser fluence and laser pulse duration.},
doi = {10.1063/1.5023008},
journal = {Physics of Plasmas},
issn = {1070-664X},
number = 8,
volume = 25,
place = {United States},
year = {2018},
month = {7}
}

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Works referenced in this record:

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