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  • Jim BaileySandia National Laboratories

    jebaile@sandia.gov

    Sandia is a multiprogram laboratory operated by Sandia Corporation, a Lockheed Martin Company, for the United States Department of Energys National Nuclear Security Administration under contract DE-AC04-94AL85000.

    HEDLP WorkshopAugust 26, 2008

    8 10 12 140.0

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    stellar interior iron transitions

    Laboratory Astrophysics at Z: Stellar Interior Opacities

  • 2Many people and institutions contribute to this work

    J.E. Bailey, G.A. Rochau, P.W. Lake, G.A. Chandler, T.J. Nash, D. Nielsen, J. TorresSandia National Laboratories, Albuquerque, N.M., 87185-1196

    C.A. IglesiasUniversity of California, Lawrence Livermore National Laboratory, Livermore, CA, 94550

    J. Abdallah Jr.Theoretical Division, Los Alamos National Laboratory, Los Alamos, NM 87545

    J.J. MacFarlane, I. Golovkin, P. WangPrism Computational Sciences, Madison, WI

    R.C. ManciniUniversity of Nevada, Reno, NV

    C. Blancard, Ph. Cosse, G. Faussurier, F. Gilleron, S. Mazevet, J.C. PainCommissariat lEnergie Atomique, CEA/DIF, B.P. 12, 91680 Bruyres-le-Chtel, France

    M. Bump, O. Garcia, and T.C. MooreK-Tech Corporation, Albuquerque, NM

  • 3Modern HED facilities can provide essential stellar physics opacity knowledge

    core

    zoneradiative

    convectivezone

    2007 Don Dixon / cosmographica.com

    Stellar structure depends on opacities

    Predictions of the best studied star, our sun, do not agree with observations

    Solar structure depends on opacities that have never been measured

    Challenge: create and diagnose stellar interior conditions on earth

    Z opacity experiments reach T ~ 156 eV

    High T enables first studies of iron transitions important in stellar interiors

    New generation of HED facilities might simultaneously reach stellar density

  • 4Modern solar models disagree with observations. Why?

    measured boundaryRCZ = 0.713 + 0.001

    Predicted RCZ = 0.726

    Thirteen

    difference

    The CZ problem

    Bahcall et al, ApJ 614, 464 (2004).Basu & Antia Physics Reports 457, 217 (2008).

    Boundary location depends on radiation transport A 10-20% opacity change solves the CZ problem. This accuracy is a challenge experiments are needed to know if the solar problem arises in the opacities or elsewhere.

    convectionradiation

    R/R0

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    ne

  • 5To understand stars we need accurate opacities for mid-Z atoms at Te > 150 eV and ne > 1022 cm-3

    K-shell oxygen, K-shell neon, and L-shell iron are important at the CZ baseThe complexity of L-shell iron demands special scrutinyThe importance of any single element is diluted by the mixture

    Example: Changing Fe L-shell by 1.5x causes ~11% change in total mean opacity

    Badnell et. al. MNRAS 360, 458 (2005).

    h

    (eV)

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    total

    iron

    Opacity Project calculations at bottom of solar convection zoneTe =193 eV, ne =1x1022 cm-3

  • 6Opacity experiment challenges grow as temperature and density increase

    tamper (low Z)sample

    heating x-rays

    backlighter

    spectrometerspectrometer

    Comparison of unattenuated and attenuated spectra determines transmissionT = exp {x} At high temperature:More energy in heating x-rays is required to produce uniform conditionsA brighter backlighter is required to overwhelm the self emission

  • 7Z opacity experiments reach T ~ 156 eV, two times higher than in prior Fe research

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    Fe + Mg at Te ~ 156 eV, ne ~ 6.9x1021 cm-3

    Fe XVI-XX

    Mg XI

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    Mg is the thermometer, Fe is the test element

    Fe & Mg sample

    radiationsource

    X-rays

    J.E. Bailey et al., PRL 99, 265002 (2007)

  • 8Opacity experiment priority: produce the charge states found in stellar interiors

    Transitions in Fe with L-shell vacancies are important in the sun Laboratory experiments must produce high enough temperatures to ionize Fe into the L shell

    Fe charge state

    f

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    +14(Mg)

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    0.4 Z conditions 150 eV, 8.6 x 1021 cm-3

    Solar CZ boundary193 eV, 1 x 1023 cm-3

    The charge state distribution depends on Te /ne and it strongly affects both bound-bound and bound-free transitions

  • 9Modern detailed opacity models are in remarkable overall agreement with the Fe data

    800 900 1000 1100 1200 1300 0.0

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    Red = MUTAJ. Abdallah, LANL

    Red = OPALC. Iglesias, LLNL

    Red = PRISMSPECTJ. MacFarlane, PRISM

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    Red = OPASOPAS team, CEA

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  • 10

    The OP model used in solar research predicts Fe L- shell opacity that is too low at Z conditions

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    Red= Z dataBlue=OP2 = 16

    Red= Z dataBlue=OPAS2 = 3.7t r

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    OP Rosseland mean is ~ 1.5x lower than OPAS at Z conditions.If this difference persisted at solar conditions, it would solve the CZ problem

  • 11

    Discrepancies at Z conditions raise a caution flag for solar opacities

    At the base of the convection zone (T=193 eV, ne =1023cm-3):Iron frequency-dependent opacities possess some differences.But Rosseland mean opacities are not significantly different, even though they disagree at Z conditions. Why?

    h(eV)

    (cm2/g)

    Red=OP - R =2606 cm2/gGreen=OPAS - R =2646 cm2/gBlue = OPAL - R =2731 cm2/g

  • 12

    Experiments at higher density are a logical next step in stellar opacity research

    We need to overcome the desire of the sample to expand when it is heated!

    Increased tamping

    Employ large low Z samples with dilute Fe concentration

    Deliberately shock sample

    Probe dynamic hohlraum interior

    All options will likely require the greater heating x-rays and brighter backlighting available on the refurbished Z or the NIF

  • 13

    Modern HED facilities can provide essential stellar physics opacity knowledge

    core

    zoneradiative

    convectivezone

    2007 Don Dixon / cosmographica.com

    JBs Prioritized list of new research for stars:

    1. Iron L shell at density and temperature high enough to test Stark broadening and continuum lowering physics (ne ~ 1022 cm-3, Te ~ 160 eV).

    2. Effect of mixed low-Z and mid-Z elements (ion dynamics, influence on wavefunctions)

    3. Oxygen and neon.

    JBs Prioritized list of new research for IFE:

    1.Cu and Ge L shell

    2. Effect of mixed low Z and mid Z

    Laboratory Astrophysics at Z:Stellar Interior OpacitiesMany people and institutions contribute to this work Modern HED facilities can provide essential stellar physics opacity knowledge Modern solar models disagree with observations. Why? To understand stars we need accurate opacities for mid-Z atoms at Te > 150 eV and ne > 1022 cm-3 Opacity experiment challenges grow as temperature and density increase Z opacity experiments reach T ~ 156 eV, two times higher than in prior Fe researchOpacity experiment priority: produce the charge states found in stellar interiorsModern detailed opacity models are in remarkable overall agreement with the Fe data The OP model used in solar research predicts Fe L-shell opacity that is too low at Z conditions Discrepancies at Z conditions raise a caution flag for solar opacitiesExperiments at higher density are a logical next step in stellar opacity researchModern HED facilities can provide essential stellar physics opacity knowledge