Bulletin of the American Physical Society
64th Annual Meeting of the APS Division of Plasma Physics
Volume 67, Number 15
Monday–Friday, October 17–21, 2022; Spokane, Washington
Session JO06: HEDP Laboratory Astrophysics on ZLive Streamed
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Chair: Brent Jones, Sandia National Laboratories Room: Ballroom 111 C |
Tuesday, October 18, 2022 2:00PM - 2:12PM |
JO06.00001: Recent Progress at the Wootton Center for Astrophysical Plasma Properties Don E Winget We explore recent physical and astrophysical progress in the current suite of experiments conducted by the Wootton Center for Astrophysical Plasma Properties (WCAPP) on the Z-machine at Sandia National Laboratories (SNL), as well as preliminary results from a new series of experiments, begun last year, at NIF. This work is fundamental. Our goal is to benchmark models and improve our understanding of the Sun and Sun-like stars, white dwarf stars and radiation dominated plasma in accretion disks around compact objects–including supermassive black holes at the centers of galaxies. We will also be in a position to contribute to cross calibrating the NIF and Z opacity platforms. The talks that follow in this section will detail the progress we have made in each of these areas. |
Tuesday, October 18, 2022 2:12PM - 2:24PM |
JO06.00002: Laboratory Observations of Hydrogen Balmer Line Profiles Bart H Dunlap, Michael H Montgomery, Bryce Hobbs, Patricia B Cho, Don E Winget, Georges S Jaar, Thomas A Gomez, Marc-Andre Schaeuble, Taisuke Nagayama, James E Bailey As the endpoints of stellar evolution, white dwarf stars contain a wealth of information about the star formation history of Galactic stellar populations, inform our understanding of cosmologically relevant type Ia supernovae, and provide us with proxy laboratories for studying matter at extreme energy densities. These and many other results stemming from the observations of white dwarf stars depend on accurate white dwarf model spectra, which, in turn, depend on accurate theoretical line profiles. The white dwarf photosphere experiment uses the Z machine at Sandia National Labs to recreate the plasma conditions observed in the line-forming regions of white dwarf atmospheres (1 – 2 eV and 1016 – 1018 cm-3) with the goal of making benchmark measurements of line profiles. In this talk, we review our progress in measuring hydrogen Balmer line profiles in absorption and emission, including measurements at higher densities (~ 1018 cm-3). We also discuss existing model uncertainties and how these and future measurements can provide useful constraints. |
Tuesday, October 18, 2022 2:24PM - 2:36PM |
JO06.00003: Revisiting iron opacity measurements at solar interior temperatures Taisuke Nagayama, James E Bailey, Guillaume P Loisel, Daniel C Mayes, Greg Dunham Since solar abundance was renewed in 2005, solar models and helioseismology disagree. One hypothesis is that calculated iron opacity used in the solar model is underestimated. In 2015, we measured iron opacity at solar interior temperatures using Z machine at Sandia National Laboratories and revealed significant discrepancies with calculated opacities. If the measurements are correct, the calculated iron opacity is severely underestimated, which can partially explain the solar puzzle. However, the reported opacity discrepancies were more than expected and aroused a controversy in the community. Since then, we performed more than 20 experiments and refined the analysis methods to improve the accuracy of the results. We will present how the final opacities and their uncertainties changed with the analysis refinements and the increased number of opacity measurements. |
Tuesday, October 18, 2022 2:36PM - 2:48PM |
JO06.00004: Oxygen opacity experiments to advance our understanding of stellar interiors Daniel C Mayes, James E Bailey, Guillaume P Loisel, Taisuke Nagayama, Theodore S Perry, Robert F Heeter, Donald E Winget, Michael H Montgomery, Stephanie B Hansen, Thomas A Gomez, Christopher J Fontes, David P Kilcrease, James Colgan The “solar problem” was revealed when a change in measured solar abundances produced disagreement between solar model predictions and helioseismic measurements. The discrepancy could be resolved if the opacity of materials at conditions near the convection zone base (CZB) is higher than predicted by models. Oxygen and iron are among the most important contributors to opacity near the solar CZB. Previous experiments with iron showed notable differences between theory and experiment. To further investigate this topic, we have begun using the previously developed opacity platforms at Z and NIF to study oxygen opacity at the relevant conditions. Measurements of oxygen opacity have been carried out using SiO2 and/or MgO samples at each facility. In this talk, we will discuss the experimental platforms, the methods used for diagnosing experiment conditions, as well as some of the preliminary results from each platform. |
Tuesday, October 18, 2022 2:48PM - 3:00PM |
JO06.00005: Laboratory tests of hypotheses for the super-solar Fe abundance problem in black hole accretion disks Patricia B Cho, Guillaume P Loisel, Taisuke Nagayama, Isaac D Huegel, Daniel C Mayes, Tim Kallman, Javier A Garcia We will present data of the first ever Fe L-shell x-ray emission spectra from laboratory photoionized plasmas on the Z facility. Such data have been a laboratory astrophysics goal for two decades but are even more critical now because of the "Super-Solar" Fe abundance problem. Fe abundances in accretion disks inferred from x-ray spectra emitted by photoionized plasma surrounding about a dozen black holes appear to contain 5-20 times more iron than the Sun. This contradicts the widely held expectation that most objects in the universe have the Sun's composition. One prevailing theory is that effects of high electron density are not properly accounted for in the models. Reinterpreting the x-ray spectra with updated high density models resolved much of the discrepancy partly because of differences predicted in the Fe L-shell emission features. However, laboratory benchmarks for photoionized plasma models have not been available until now. The platform mimics the photon flux, density, and temperature conditions in black hole accretion disks, and we control the composition, uniformity, and spectral resolution. We also measured photoionized calcium K-shell spectra as a surrogate for Fe K-shell spectra from black holes. The relativistically broadened iron K emission features also have the potential to strongly influence black hole fundamental parameters. We will describe our progress using the data to evaluate model accuracy and its potential to inform the Super-Solar Fe abundance problem. |
Tuesday, October 18, 2022 3:00PM - 3:12PM |
JO06.00006: Characterizing charge state distributions in Fe photoionized plasma to test high density effects in astrophysical code XSTAR Isaac D Huegel, Patricia B Cho, Daniel C Mayes, Guillaume P Loisel Astrophysical plasma codes predict unreasonably high iron abundances in the photoionized plasmas found in about a dozen black hole accretion disks. It has been suggested that this discrepancy may stem from an underestimate of electron densities and subsequent neglect of high-density effects. One astrophysical model, XSTAR, was recently updated to incorporate physical mechanisms like continuum lowering which could significantly affect the emergent spectra at high densities. However, photoionized plasma codes have not been validated against observation due to the difficulty to produce photoionized plasmas in the lab. Using the Z-machine at Sandia National Laboratories, we developed a platform to collect emission and absorption spectra from photoionized Fe plasmas. Ultimately, our goal is to evaluate XSTAR's ability to accurately predict x-ray emission and absorption spectra. This will inform the accuracy of revisions to iron abundances inferred in black hole accretion disks. In addition to comparing model spectra against observations, one key intermediate component of the code we can test is the predicted charge state distribution. We perform fits to the observed absorption features using opacity cross sections calculated using the collisional-radiative code PrismSPECT to infer ionization fractions of the charge states achieved in the plasma. This method allows us to establish a measurement of the ionization fractions that is independent of the model assumptions. We will describe the motivation, approach, and preliminary results comparing observed and predicted charge state distributions. |
Tuesday, October 18, 2022 3:12PM - 3:24PM |
JO06.00007: Effects of Element Abundance on Temperature and Charged State Distribution in Laboratory Photoionized Plasmas Georges S Jaar, Roberto C Mancini, Kyle Swanson, Daniel C Mayes The matter in many astrophysical systems can be described as a photoionized plasma. These plasmas consist of multiple elements but are mostly hydrogen dominated. Despite their small concentrations, heavier elements play a dominant role in the physics of these systems and are not well understood. We present experimental and simulation results for neon-hydrogen mixed laboratory photoionized plasmas in which we survey the effects of changing neon abundance on the electron temperature and charged state distribution. The results suggest that the temperature is strongly coupled to neon abundance. The experiments were performed on the Z Machine at Sandia National Labs where a cell filled with neon-hydrogen gas was driven by the x-ray flux produced by a wire array z-pinch implosion. X-ray transmission spectroscopy was used to measure the charged state distribution and electron temperature. The simulations were performed using HELIOS-CR, a 1D radiation-hydrodynamics code with inline atomic kinetics. |
Tuesday, October 18, 2022 3:24PM - 3:36PM |
JO06.00008: Photoionized plasma experiments at OMEGA EP Roberto C Mancini, Jeffrey J Rowland, Ryan P Schoenfeld, Kyle Swanson, D Mayes, Robert F Heeter, Ed V Marley, D A Liedahl, Sean P Regan A new platform has been established at the OMEGA EP laser facility in which a tamped silicon sample is driven by a three-Cu halfraum x-ray source that produces a 30ns-duration, broadband x-ray flux with a radiation temperature of 90eV. The x-ray source performance is monitored with VISAR and its spectral distribution is recorded with a grating spectrometer. Plasma density is determined from the expansion measurement performed with an imaging grating instrument, and charged state distribution and temperature are extracted from the analysis of the silicon K-shell line absorption spectrum recorded with a crystal spectrometer. The latter diagnostic is afforded by using a separate laser beam to drive a short-duration source of backlighting photons. Probing the silicon plasma at different times provides an experimental check of the steady-state condition in the photoionized plasma. We discuss the observations recorded during a series of campaigns at OMEGA EP and the comparisons with radiation-hydrodynamics and astrophysical modeling codes. |
Tuesday, October 18, 2022 3:36PM - 3:48PM |
JO06.00009: Photoionized gas jet experiments at the 1 MA Zebra pulsed-power driver relevant to astrophysics Kyle J Swanson, Roberto C Mancini, Vladimir V Ivanov, Daniel C Mayes, Enac Gallardo-Diaz, Ryan P Schoenfeld, Alexey L Astanovitskiy, Bernhard Bach, Jeffrey J Rowland, Noah A Huerta The photoionized supersonic gas jet platform developed on the 1 MA Zebra accelerator provides the first method for university-scale laboratory photoionized plasma studies with astrophysical relevance. A millimeter scale cylindrical volume of gas is irradiated with an intense broadband x-ray flux produced by the implosion of a wire-array z-pinch, which heats and backlights the plasma. The photoionized gas jet platform employs laser and x-ray diagnostics, which provide measurements of atomic and electron densities as well as charge state distribution (CSD). These measurements are used to inform, constrain, and test theory models. Radial atomic density profiles of the neutral gas jet and the characterized spectral distribution of the x-ray radiation drive are used to initialize 1D radiation hydrodynamic simulations of the experiment. Simulation results are compared with electron density maps extracted from dual color air-wedge shearing laser interferometry, and synthetic transmission spectra and CSD are tested against measurements obtained with a crystal spectrometer. |
Tuesday, October 18, 2022 3:48PM - 4:00PM |
JO06.00010: Modeling of temperature and ionization of laboratory photoionized plasmas Jeffrey J Rowland, Roberto C Mancini, Daniel C Mayes Measurements of the electron temperature in laboratory photoionized plasma experiments have shown significant discrepancies with predictions computed with steady-state astrophysical models. However, radiation-hydrodynamics simulations of the experiments including inline, time-dependent atomic physics have produced good temperature comparisons between theory and observation.1 We discuss differences in the physics models employed in astrophysical and radiation-hydrodynamics codes. Additionally, we use the new capability of astrophysics model codes to include transient effects in the energy and level population dynamics to recompute our previous model calculations. Temperatures computed with astrophysics models that account for time-dependent effects compare much better with measurements and thus to radiation-hydrodynamics predictions as well. |
Tuesday, October 18, 2022 4:00PM - 4:12PM |
JO06.00011: A statistical approach to Stark broadening for complex ions Kelsey Adler, Thomas A Gomez, Nathaniel R Shaffer, Charles Starrett, Stephanie B Hansen Lineshapes encode a wealth of information about the plasmas that produce them, including plasma composition, density, temperature, motion and rotation, and magnitude of electric and magnetic fields. In particular, Stark broadening encodes information about the electric microfields generated by neighboring ions in a plasma and is a valuable density diagnostic. Producing lineshapes for complex atoms with 3 or more active electrons using standard perturbation theory can have prohibitively high computational costs. We present a simple and computationally straightforward heuristic model that can be used for ions of any complexity. Our statistical approach uses transition energies, energy shifts, and radial density distributions from a self-consistent average atom code to produce Stark-broadened lineshapes. We present comparisons to standard line-broadening methods for lines from one-and two-electron aluminum ions. |
Tuesday, October 18, 2022 4:12PM - 4:24PM |
JO06.00012: A First-Principles Study of L-Shell Iron and Chromium Opacity at Stellar Interior Conditions Valentin V Karasiev, Suxing Hu, Nathaniel R Shaffer, Gennady Miloshevsky
1 V. V. Karasiev and S. X. Hu, Phys. Rev. E 103, 033202 (2021). 2 G. Miloshevsky et al., Phys. Rev. E 92, 033109 (2015). 3 J.E. Bailey et al., Nature 517, 56 (2015). 4 T. Nagayama et al., Phys. Rev. Lett. 122, 235001 (2019).
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