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Title: Examining the radiation drive asymmetries present in the high foot series of implosion experiments at the National Ignition Facility

Abstract

This paper details and examines the origins of radiation drive asymmetries present during the initial High Foot implosion experiments. Such asymmetries are expected to reduce the stagnation pressure and the resulting yield of these experiments by several times. Analysis of reemission and dual axis shock timing experiments indicates that a flux asymmetry, with a P2/P0 amplitude that varies from -10 to -5 %, is present during the first shock of the implosion. This first shock asymmetry can be corrected through adjustments to the laser cone fraction. A thin shell model and more detailed radiation hydrodynamic calculations indicate that an additional negative P2/P0 asymmetry during the second or portions of the third shock is required to reach the observed amount of asymmetry in the shape of the ablator at peak implosion velocity. In conjunction with symmetry data from the x-ray self emission produced at stagnation, these models also indicate that after the initially negative P2/P0 flux asymmetry, the capsule experiences a positive P2/P0 flux asymmetry that develops at or before ~2 ns into the peak of the laser power. Here, direct evidence for this inference, using measurements of the x-ray emission produced by the lasers irradiating the hohlraum, is presented. Thismore » data indicates that the reduction in the transmitted inner laser cone energy results from impeded propagation through the plasma associated with the ablation of the capsule target. This paper also correlates measurements of the outer cone laser deposition location with variations in the observed x-ray self emission shape from experiments conducted with nominally the same input conditions.« less

Authors:
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  1. Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
  2. Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
Publication Date:
Research Org.:
Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
Sponsoring Org.:
USDOE
OSTI Identifier:
1378553
Alternate Identifier(s):
OSTI ID: 1348041
Report Number(s):
LLNL-JRNL-718397
Journal ID: ISSN 1070-664X; PHPAEN
Grant/Contract Number:
AC52-07NA27344
Resource Type:
Journal Article: Accepted Manuscript
Journal Name:
Physics of Plasmas
Additional Journal Information:
Journal Volume: 24; Journal Issue: 5; Journal ID: ISSN 1070-664X
Publisher:
American Institute of Physics (AIP)
Country of Publication:
United States
Language:
English
Subject:
70 PLASMA PHYSICS AND FUSION; Hohlraum; X-rays; Laser ablation; Shell model; X-ray imaging

Citation Formats

Pak, A., Divol, L., Kritcher, A. L., Ma, T., Ralph, J. E., Bachmann, B., Benedetti, L. R., Casey, D. T., Celliers, P. M., Dewald, E. L., Döppner, T., Field, J. E., Fratanduono, D. E., Berzak Hopkins, L. F., Izumi, N., Khan, S. F., Landen, O. L., Kyrala, G. A., LePape, S., Millot, M., Milovich, J. L., Moore, A. S., Nagel, S. R., Park, H. -S., Rygg, J. R., Bradley, D. K., Callahan, D. A., Hinkel, D. E., Hsing, W. W., Hurricane, O. A., Meezan, N. B., Moody, J. D., Patel, P., Robey, H. F., Schneider, M. B., Town, R. P. J., and Edwards, M. J. Examining the radiation drive asymmetries present in the high foot series of implosion experiments at the National Ignition Facility. United States: N. p., 2017. Web. doi:10.1063/1.4979192.
Pak, A., Divol, L., Kritcher, A. L., Ma, T., Ralph, J. E., Bachmann, B., Benedetti, L. R., Casey, D. T., Celliers, P. M., Dewald, E. L., Döppner, T., Field, J. E., Fratanduono, D. E., Berzak Hopkins, L. F., Izumi, N., Khan, S. F., Landen, O. L., Kyrala, G. A., LePape, S., Millot, M., Milovich, J. L., Moore, A. S., Nagel, S. R., Park, H. -S., Rygg, J. R., Bradley, D. K., Callahan, D. A., Hinkel, D. E., Hsing, W. W., Hurricane, O. A., Meezan, N. B., Moody, J. D., Patel, P., Robey, H. F., Schneider, M. B., Town, R. P. J., & Edwards, M. J. Examining the radiation drive asymmetries present in the high foot series of implosion experiments at the National Ignition Facility. United States. doi:10.1063/1.4979192.
Pak, A., Divol, L., Kritcher, A. L., Ma, T., Ralph, J. E., Bachmann, B., Benedetti, L. R., Casey, D. T., Celliers, P. M., Dewald, E. L., Döppner, T., Field, J. E., Fratanduono, D. E., Berzak Hopkins, L. F., Izumi, N., Khan, S. F., Landen, O. L., Kyrala, G. A., LePape, S., Millot, M., Milovich, J. L., Moore, A. S., Nagel, S. R., Park, H. -S., Rygg, J. R., Bradley, D. K., Callahan, D. A., Hinkel, D. E., Hsing, W. W., Hurricane, O. A., Meezan, N. B., Moody, J. D., Patel, P., Robey, H. F., Schneider, M. B., Town, R. P. J., and Edwards, M. J. Fri . "Examining the radiation drive asymmetries present in the high foot series of implosion experiments at the National Ignition Facility". United States. doi:10.1063/1.4979192. https://www.osti.gov/servlets/purl/1378553.
@article{osti_1378553,
title = {Examining the radiation drive asymmetries present in the high foot series of implosion experiments at the National Ignition Facility},
author = {Pak, A. and Divol, L. and Kritcher, A. L. and Ma, T. and Ralph, J. E. and Bachmann, B. and Benedetti, L. R. and Casey, D. T. and Celliers, P. M. and Dewald, E. L. and Döppner, T. and Field, J. E. and Fratanduono, D. E. and Berzak Hopkins, L. F. and Izumi, N. and Khan, S. F. and Landen, O. L. and Kyrala, G. A. and LePape, S. and Millot, M. and Milovich, J. L. and Moore, A. S. and Nagel, S. R. and Park, H. -S. and Rygg, J. R. and Bradley, D. K. and Callahan, D. A. and Hinkel, D. E. and Hsing, W. W. and Hurricane, O. A. and Meezan, N. B. and Moody, J. D. and Patel, P. and Robey, H. F. and Schneider, M. B. and Town, R. P. J. and Edwards, M. J.},
abstractNote = {This paper details and examines the origins of radiation drive asymmetries present during the initial High Foot implosion experiments. Such asymmetries are expected to reduce the stagnation pressure and the resulting yield of these experiments by several times. Analysis of reemission and dual axis shock timing experiments indicates that a flux asymmetry, with a P2/P0 amplitude that varies from -10 to -5 %, is present during the first shock of the implosion. This first shock asymmetry can be corrected through adjustments to the laser cone fraction. A thin shell model and more detailed radiation hydrodynamic calculations indicate that an additional negative P2/P0 asymmetry during the second or portions of the third shock is required to reach the observed amount of asymmetry in the shape of the ablator at peak implosion velocity. In conjunction with symmetry data from the x-ray self emission produced at stagnation, these models also indicate that after the initially negative P2/P0 flux asymmetry, the capsule experiences a positive P2/P0 flux asymmetry that develops at or before ~2 ns into the peak of the laser power. Here, direct evidence for this inference, using measurements of the x-ray emission produced by the lasers irradiating the hohlraum, is presented. This data indicates that the reduction in the transmitted inner laser cone energy results from impeded propagation through the plasma associated with the ablation of the capsule target. This paper also correlates measurements of the outer cone laser deposition location with variations in the observed x-ray self emission shape from experiments conducted with nominally the same input conditions.},
doi = {10.1063/1.4979192},
journal = {Physics of Plasmas},
number = 5,
volume = 24,
place = {United States},
year = {Fri Mar 24 00:00:00 EDT 2017},
month = {Fri Mar 24 00:00:00 EDT 2017}
}

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