• Director: Don Winget
• Deputy Director: Mike Montgomery
• DOE award number: DE-FOA-0001634
• Executive Assistant: Dolores Groves

Overview

The Wootton Center for Astrophysical Plasma Properties (WCAPP) will focus on atomic and radiation physics of matter in a wide range of temperatures and densities. Although motivated by astrophysics, the Center will address problems of interest for stockpile stewardship, ICF, HED physics and astrophysics. The CAPP team will use spectra at wavelengths from X-ray to optical to diagnose plasmas and compare with observations of astrophysical objects and similar plasmas. This work will have a strong experimental emphasis but incorporate a range of theorists and modelers for code validation. This will sharpen the scientific impact of the experiments and their contribution to NNSA.

Our team will include university, National Laboratory, and NASA scientists. These scientists, with diverse specialties, represent all career stages from the most junior to the most senior. Through immersive, team building interactions before, during, and after Z-shot series at SNL, observations at McDonald Observatory, and meetings, the students, postdocs, and junior faculty will grow as scientists. They will be introduced in a practical way to the atmosphere, work environment, and opportunities of National Laboratories. Students will be recruited through interest in astrophysics, extreme physics, and/or energy science. Hence, the Center will contribute to produce a pool of potential candidates for employment in NNSA National Laboratories.

Project Objectives

The conditions that exist inside stars and accretion disks around compact objects have similarities and direct implications for many ICF and HED experiments carried out on the NNSA's National facilities. At lower temperatures, the validation of spectral models used to interpret the conditions of white dwarf stars are directly applicable to studying the plasmas formed in the power-flow region on Z. We create macroscopic plasmas and study their time evolution, including transitions from strong non-equilibrium conditions evolving into equilibrium during a single shot. New experiments motivate new platforms, diagnostics, and developments in theory and modeling. These aid the programmatic NNSA missions of the facility through amplified capabilities; the multi-experiment approach increases efficiency by factors of 4 to 5.

The CAPP directly addresses the need to develop a cadre of top researchers in areas of atomic physics and radiation transport by concentrating on atomic processes and spectroscopy in plasmas that are at HED conditions and/or are bathed in strong x-ray radiation fields. CAPP will create a layered-mentoring approach that will guarantee a nurturing but challenging atmosphere that will yield a steady pipeline of talented young scientists. This center will be a training ground for future stewards of the NNSA mission.

Current Projects

The projects explored within CAPP are varied. Below, we list the astrophysical problems, the suspected problem with atomic processes, and how to answer those problems.

I. Solar Opacity (SNL)

• Problem: The solar convection zone boundary measured by helioseismology is discrepant with the standard solar model. This discrepancy can be resolved with a 14% increase in the Rosseland Mean Opacity.
• Hypothesis: Opacity is incorrectly modeled.
• Method: Heat a sample of iron to solar interior conditions to measure opacity in absorption (see Bailey et al. 2015).

II. White Dwarf Spectral Line-Broadening (UT)

• Problem: Spectroscopic method of determining white dwarf masses is discrepant with gravitational redshift and orbital determination of mass.
• Hypothesis: Spectral Line Broadening is inaccurate.
• Method: Heat samples of hydrogen and helium gasses to white dwarf atmospheric conditions and measure emission and absorption spectra and compare to models (see Montgomery et al. 2015).

III. Efficiency of RAD (SNL)

• Problem: Is Resonant Auger Destruction (RAD) the explanation for missing iron lines in accretion disks?
• Hypothesis: RAD is not 100% efficient in destroying emission lines
• Method: Heat sample of silicon in high-radiation environment, measure spectrum in emission and absorption to measure relative strengths of spectral lines and how they are affected by RAD (see Loisel et al. 2017).

IV. Heating in Accretion Disks (UNR)

• Problem: Accretion disk models rely on untested atomic kinetics models.
• Hypothesis: The current models (XSTAR, CLOUDY) are not accurately capturing atomic kinetics properly.
• Method: Heat neon to accretion disk conditions and compare charge-states and line strengths with the predictions of astrophysical codes (Mancini et al. 2017).

Administrative Function of CAPP

This center was established to provide continued funding of these long-term projects, including graduate student education. We are currently seeking potential graduate students and postdocs, as well as other collaborators. Projects are not limited to the ones listed, or to the facilities or universities that are already involved in the project. Work within the center may involve both travel and telecommuting to the facility where the experiment is performed (such as SNL).

Current funding allows for up to 6 graduate students and 3 postdocs. In addition to SNL, we plan to perform experiments at other facilities, including the National Ignition Facility at Lawrence Livermore National Laboratory. We are also seeking additional projects to perform at these facilities that can explore other important astrophysical problems. The graduate students and postdocs that work with us will be exposed to research opportunities at the National Laboratories

Acknowldegements:

The CAPP is supported through the NNSA Stockpile Stewardship Academic Alliance program funded by the DOE through grant DE-FOA-0001634. Aspects of the white dwarf science are additionally supported by the NSF under grant AST-1312983.

Press Releases and News Stories

• UT Press Release about the new Wootton Center for Astrophysical Plasma Properties (WCAPP)
• KUT story with Don Winget and Mike Montgomery about the new Wootton Center for Astrophysical Plasma Properties (WCAPP)
• NPR story with Don Winget about our science collaboration on the Z machine at Sandia National Labs
• NPR story with Don Winget about accepted wisdom in science
• A short article in Discover Magazine about our white dwarf photosphere experiments on the Z Machine at Sandia National Laboratory
• Three recent StarDate broadcasts featuring our science: Star in a Bottle, White Dwarf Quakes, Cosmic Clocks

Refereed Publications

• Density-matrix correlations in the relaxation theory of electron broadening, Gomez, T. A., Nagayama, T., Kilcrease, D. P., Montgomery, M. H., Winget, D. E., 2018, Phys. Rev. A, 98(1), 012505
• WDEC: A Code for Modeling White Dwarf Structure and Pulsations, Bischoff-Kim, A. Montgomery, M. H., 2018, AJ, 155, 187
• Matrix Methods for Solving Hartree-Fock Equations in Atomic Structure Calculations and Line Broadening, Gomez, T. A., Nagayama, T., Fontes, C., Kilcrease, D. P., Hansen, S., Montgomery, M. H., & Winget, D. E., 2018, Atoms, 6, 22
• Effect of higher-order multipole moments on the Stark line shape, Gomez, T. A., Nagayama, T., Kilcrease, D. P., Montgomery, M. H., & Winget, D. E., 2016, Phys. Rev. A, 94, 022501
• Laboratory Measurements of White Dwarf Photospheric Spectral Lines: H-beta, Falcon, R. E., Rochau, G. A., Bailey, J. E., Gomez, T. A., Montgomery, M. H., Winget, D. E., & Nagayama, T., 2015, ApJ, 806, 214
• An experimental platform for creating white dwarf photospheres in the laboratory: Preliminary results, Montgomery, M. H., Falcon, R. E., Rochau, G. A., Bailey, J. E., Gomez, T. A., Carlson, A. L., Bliss, D. E., Nagayama, T., Stein, M., & Winget, D. E., 2015, High Energy Density Physics, 17, 168
• An experimental platform for creating white dwarf photospheres in the laboratory, Falcon, R. E., Rochau, G. A., Bailey, J. E., Ellis, J. L., Carlson, A. L., Gomez, T. A., Montgomery, M. H., Winget, D. E., Chen, E. Y., Gomez, M. R., & Nash, T. J., 2013, High Energy Density Physics, 9, 82-90
• A Gravitational Redshift Determination of the Mean Mass of White Dwarfs: DBA and DB Stars, Falcon, R. E., Winget, D. E., Montgomery, M. H., Williams, K. A., 2012, ApJ, 757, 116
• A Gravitational Redshift Determination of the Mean Mass of White Dwarfs. DA Stars, Falcon, R. E., Winget, D. E., Montgomery, M. H., & Williams, K. A., 2010, ApJ, 712, 585

Conference Proceedings

• Influence of Projection Operator on Oxygen Line Shapes and its effect on Rosseland-Mean Opacity in Stellar Interiors, Gomez, T., Nagayama, T., Kilcrease, D., Hansen, S., Montgomery, M., & Winget, D., 2018, In American Astronomical Society Meeting Abstracts 231, volume 231 of American Astronomical Society Meeting Abstracts, 452.02
• Numerical simulation of DA white dwarf surface convection, Zaussinger, F., Kupka, F., Montgomery, M., & Egbers, C., 2018, Journal of Physics: Conference Series, 1031(1), 012013
• Helium at White Dwarf Photospheric Conditions: Preliminary Laboratory Results, Schaeuble, M., Falcon, R. E., Gomez, T. A., Winget, D. E., Montgomery, M. H., & Bailey, J. E., 2017, In 20th European White Dwarf Workshop, ed. P.-E. Tremblay, B. Gaensicke, & T. Marsh, volume 509 of Astronomical Society of the Pacific Conference Series, 231
• From the Telescope to the Laboratory and Back Again: The Center for Astrophysical Plasma Properties, Montgomery, M. H., Winget, D., Schaeuble, M., Hawkins, K., & Wheeler, C., 2018, In American Astronomical Society Meeting Abstracts 231, volume 231 of American Astronomical Society Meeting Abstracts, 443.01
• A survey of pulsating DA and DB white dwarfs Observations with the Whole Earth Telescope, Provencal, J. L., Montgomery, M., & Shipman, H., 2017, In European Physical Journal Web of Conferences, volume 152 of European Physical Journal Web of Conferences, 01012
• Modeling the Spectra of Dense Hydrogen Plasmas: Beyond Occupation Probability, Gomez, T. A., Montgomery, M. H., Nagayama, T., Kilcrease, D. P., Winget, D. E., 2017, In 20th European White Dwarf Workshop, ed. P.-E. Tremblay, B. Gaensicke, & T. Marsh, volume 509 of Astronomical Society of the Pacific Conference Series, 143
• Reaching Higher Densities for Laboratory White Dwarf Photospheres to Measure Spectroscopic Line Profiles, Falcon, R. E., Bailey, J. E., Gomez, T. A., Schaeuble, M., Nagayama, T., Montgomery, M. H., Winget, D. E., Rochau, G. A., 2017, In 20th European White Dwarf Workshop, ed. P.-E. Tremblay, B. Gaensicke, & T. Marsh, volume 509 of Astronomical Society of the Pacific Conference Series, 149
• Which Hydrogen Balmer Lines are Most Reliable for Determining White Dwarf Atmospheric Parameters?, Falcon, R. E., Rochau, G. A., Bailey, J. E., Gomez, T. A., Montgomery, M. H., Winget, D. E., & Nagayama, T., 2015, In 19th European Workshop on White Dwarfs, ed. P. Dufour, P. Bergeron, & G. Fontaine, volume 493 of Astronomical Society of the Pacific Conference Series, 399
• The Z Astrophysical Plasma Properties (ZAPP) Collaboration, Montgomery, M. H., Bailey, J. E., Blancard, C., Carlson, A. L., Cohen, D., Cosse, P., Dunham, G., Durmaz, T., Ellis, J. L., Falcon, R. E., Faussurier, G., Gilleron, F., Golovkin, I., Gomez, M. R., Gomez, T., Hall, I., Hansen, S. B., Iglesias, C. A., Kernaghan, M., Lake, P. W., Liedahl, D., Lockard, T., MacArthur, J., MacFarlane, J. J., Mancini, R. C., Nahar, S. N., Nash, T. J., Nielsen, D. S., Pain, J. C., Pinsonneault, M., Pradhan, A. K., Rochau, G. A., Sherrill, M., & Winget, D. E., 2012, In American Astronomical Society Meeting Abstracts 219, volume 219 of American Astronomical Society Meeting Abstracts, 238.06
• Developing an Experimental Platform to Create White Dwarf Photospheres in the Laboratory, Falcon, R., Rochau, G. A., Bailey, J. E., Ellis, J. L., Carlson, A. L., Gomez, T., Montgomery, M. H., Winget, D. E., & Gomez, M. R., 2012, In American Astronomical Society Meeting Abstracts 219, volume 219 of American Astronomical Society Meeting Abstracts, 238.07
• Creation of White Dwarf Photospheres in the Laboratory, Ellis, J., Falcon, R. E., Rochau, G. A., Winget, D. E., Bailey, J. E., & Montgomery, M. H., 2011, In American Astronomical Society Meeting Abstracts, volume 217 of American Astronomical Society Meeting Abstracts, 433.24
• Creating White Dwarf Photospheres in the Laboratory, Falcon, R. E., Rochau, G. A., Bailey, J. E., Ellis, J. L., Montgomery, M. H., Winget, D. E., Gomez, M. R., Leeper, R. J., 2010, AIP Conference Proceedings, 1273(1), 436
• A Gravitational Redshift Determination of the Mean Mass of DBA White Dwarfs, Falcon, R. E., Winget, D. E., Montgomery, M. H., & Williams, K. A., 2010, AIP Conference Proceedings, 1273(1), 13