Title: Progress towards a more predictive model for hohlraum radiation drive and symmetry

Abstract

For several years, we have been calculating the radiation drive in laser-heated gold hohlraums using flux-limited heat transport with a limiter of 0.15, tabulated values of local thermodynamic equilibrium gold opacity, and an approximate model for not in a local thermodynamic equilibrium (NLTE) gold emissivity (DCA_2010). This model has been successful in predicting the radiation drive in vacuum hohlraums, but for gas-filled hohlraums used to drive capsule implosions, the model consistently predicts too much drive and capsule bang times earlier than measured. Here, we introduce a new model that brings the calculated bang time into better agreement with the measured bang time. The new model employs (1) a numerical grid that is fully converged in space, energy, and time, (2) a modified approximate NLTE model that includes more physics and is in better agreement with more detailed offline emissivity models, and (3) a reduced flux limiter value of 0.03. We applied this model to gas-filled hohlraum experiments using high density carbon and plastic ablator capsules that had hohlraum He fill gas densities ranging from 0.06 to 1.6 mg/cc and hohlraum diameters of 5.75 or 6.72 mm. The new model predicts bang times to within ±100 ps for most experiments withmore » low to intermediate fill densities (up to 0.85 mg/cc). This model predicts higher temperatures in the plasma than the old model and also predicts that at higher gas fill densities, a significant amount of inner beam laser energy escapes the hohlraum through the opposite laser entrance hole.« less

Authors:

Jones, O. S. ^[1]; Suter, L. J. ^[1]; Scott, H. A. ^[1]; Barrios, M. A.  ^[1];

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Farmer, W. A.  ^[1];

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Hansen, S. B. ^[2]; Liedahl, D. A. ^[1]; Mauche, C. W. ^[1]; Moore, A. S. ^[1]; Rosen, M. D. ^[1]; Salmonson, J. D. ^[1]; Strozzi, D. J.  ^[1];

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Thomas, C. A.  ^[1];

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Turnbull, D. P. ^[3]

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+ Show Author Affiliations

1. Lawrence Livermore National Laboratory, Livermore, California 94551, USA
2. Sandia National Laboratory, Albuquerque, New Mexico 87185, USA
3. Laboratory for Laser Energetics, Rochester, New York 14623, USA

Publication Date:

Fri May 19 00:00:00 EDT 2017

Research Org.:

Lawrence Livermore National Laboratory (LLNL), Livermore, CA (United States)

Sponsoring Org.:

USDOE National Nuclear Security Administration (NNSA)

OSTI Identifier:

1375645

Alternate Identifier(s):

OSTI ID: 1421189; OSTI ID: 1474378

Report Number(s):

LLNL-JRNL-719477
Journal ID: ISSN 1070-664X; 10.1063/1.4982693

Grant/Contract Number:  

AC52-07NA27344

Resource Type:

Journal Article: Published Article

Journal Name:

Physics of Plasmas

Additional Journal Information:

Journal Name: Physics of Plasmas 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 TECHNOLOGY; autoionization; plasma confinement; x-rays; plasma temperature; spectroscopy; transition metals; chemical elements; speed of sound; plasma instabilities; thermodynamic states and processes