57th Annual Meeting of the APS Division of Plasma Physics
Volume 60, Number 19
Monday–Friday, November 16–20, 2015;
Savannah, Georgia
Session FR1: Review: Measuring the Opacity of Stellar Interior Matter in Terrestrial Laboratories
8:00 AM–9:00 AM,
Tuesday, November 17, 2015
Room: Chatham Ballroom AB
Chair: Stephanie Hansen, Sandia National Laboratories
Abstract ID: BAPS.2015.DPP.FR1.1
Abstract: FR1.00001 : Measuring the opacity of stellar interior matter in terrestrial laboratories
8:00 AM–9:00 AM
Preview Abstract
Author:
James Bailey
(Sandia Natinal Laboratories)
How does energy propagate from the core to the surface of the Sun, where it
emerges to warm the Earth? Nearly a century ago Eddington [1]
recognized that the attenuation of radiation by
stellar matter controls the internal structure of stars like the sun.
Opacities for high energy density (HED) matter are challenging to calculate
because accurate and complete descriptions of the energy levels,
populations, and plasma effects such as continuum lowering and line
broadening are needed for partially ionized atoms. This requires
approximations, in part because billions of bound-bound and bound-free
electronic transitions can contribute to the opacity. Opacity calculations,
however, have never been benchmarked against laboratory measurements at
stellar interior conditions. Laboratory opacity measurements were limited in
the past by the challenges of creating and diagnosing sufficiently large and
uniform samples at the extreme conditions found inside stars. In research
conducted over more than 10 years, we developed an experimental platform on
the Z facility and measured [2] wavelength-resolved iron opacity at electron
temperatures T$_{\mathrm{e}}=$ 156-195 eV and densities n$_{\mathrm{e}}$
$=$ 0.7 -- 4.0 x 10$^{22}$ cm$^{-3}$ - conditions very
similar to the radiation/convection boundary zone within the Sun. The
wavelength-dependent opacity in the 975 -- 1775 eV photon energy range is
30-400{\%} higher than models predict. This raises questions about how well
we understand the behavior of atoms in HED plasma. These measurements may
also help resolve decade-old discrepancies between solar model predictions
and helioseismic observations. This talk will provide an overview of the
measurements, investigations of possible errors, and ongoing experiments
aimed at testing hypotheses to resolve the model-data discrepancy.
\\[4pt]
$++$Sandia is a multiprogram laboratory operated by Sandia Corporation, a
Lockheed Martin Company, for the United States Department of Energy under
contract DE-AC04-94AL85000.
\\[4pt]
[1] A.S. Eddington, The Internal Constitution of the Stars (Cambridge Univ.
Press, Cambridge, 1926).\\[0pt]
[2] J.E. Bailey et al., \textit{Nature} \textbf{517}, 56 (2015).
To cite this abstract, use the following reference: http://meetings.aps.org/link/BAPS.2015.DPP.FR1.1