Bulletin of the American Physical Society
63rd Annual Meeting of the APS Division of Plasma Physics
Volume 66, Number 13
Monday–Friday, November 8–12, 2021; Pittsburgh, PA
Session PO03: HED: Photoionized PlasmasOn Demand
|
Hide Abstracts |
Chair: Heath LeFevre, University of Michigan Room: Rooms 302-303 |
Wednesday, November 10, 2021 2:00PM - 2:12PM |
PO03.00001: Recent Progress at the Wootton Center for Astrophysical Plasma Properties Don E Winget, Michael H Montgomery, Roberto C Mancini, Bart H Dunlap, Guillaume P Loisel, Taisuke Nagayama, James E Bailey, Thomas A Gomez, Marc-Andre Schaeuble, Patricia B Cho, Daniel C Mayes, Kyle J Swanson, Robert F Heeter, Theodore S Perry, Kathy Opachich, Harry F Robey 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 this year, at NIF. This work is foundational. Upon it we build our understanding of the Sun and Sun-like stars, radiation dominated plasma in accretion disks around compact objects–including supermassive black holes at the centers of galaxies, and white dwarf stars, the compact endpoint of almost all stars. The talks that follow in this section will detail the progress we have made in each of these areas. |
Wednesday, November 10, 2021 2:12PM - 2:24PM |
PO03.00002: Increasing the Reliability of Line Profile Measurements for White Dwarf Atmospheric Models Bart H Dunlap, Michael H Montgomery, Bryce Hobbs, Patricia B Cho, Don E Winget, Thomas A Gomez, Sonal Patel, Marc-Andre Schaeuble, Taisuke Nagayama, James E Bailey, Georges S Jaar 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 e/cm3). Benchmark measurements of the line profiles used in models of white dwarf spectra are critical for assessing the reliability of fundamental white dwarf parameters derived from spectroscopic fits, which are quite sensitive to the details of the line shapes. Reliable experimental determination of line shapes requires either relatively uniform plasma along our lines of sight (~12 cm long) or an accurate characterization of any nonuniformity. In this talk, we will describe the modifications we have made to our experimental platform to allow measurements of gradients in our plasma and present the first results of these experiments. We also discuss further platform enhancements that we are implementing to reduce systematic uncertainties and increase the reliability of our line shape measurements. |
Wednesday, November 10, 2021 2:24PM - 2:36PM |
PO03.00003: A New Generation of Line Profile Calculations for Non-ideal Hydrogen Plasmas Michael H Montgomery, Patricia B Cho, Thomas A Gomez, Bart H Dunlap, Bryce Hobbs We have recently developed Xenomorph, a new simulation-based line profile code. In addition to removing many approximations inherent in the analytical approach of Vidal, Cooper, and Smith (1970; VCS) on which the standard line profiles used in astronomy are based, Xenomorph is the first simulation-based code that accommodates a prescription for occupation probability/continuum lowering and a fully randomized particle re-injection scheme. Across a wide range of temperatures and densities, we find that the resulting line profiles are most sensitive to the treatments of screening and occupation probability. We show that this has consequences for spectral fits of both laboratory plasmas and white dwarf stars. |
Wednesday, November 10, 2021 2:36PM - 2:48PM |
PO03.00004: Interrogation of laboratory photoionized plasmas using interferometry and X-ray absorption spectroscopy on the Z-machine. Kyle J Swanson, Roberto C Mancini, Georges S Jaar, Daniel C Mayes, Vladimir V Ivanov, Alexey L Astanovitskiy, Oleg Dmitriev, Aidan W Klemmer, Chris De La Cruz, Kate Bell, Daniel Dolan, Andy Porwitzky, Guillaume P Loisel, James E Bailey Photoionized plasma dynamics are crucial for understanding the universe we exist in. Laboratory astrophysics experiments play a critical role in developing this understanding. Two interferometry probes spaced 4mm apart were incorporated into a photoionized gas cell experiment on Z and used to measure electron density and assess gas cell plasma uniformity. The interferometer uses a novel implementation of photon Doppler velocimetry (PDV) to measure electron density time histories with ~1ns time resolution at multiple locations. The neon and argon K-shell line absorption spectra were measured with an elliptical crystal spectrometer equipped with KAP and PET crystals to observe the spectral ranges 850-1250eV and 2770-4575eV, respectively. The line absorption features indicate that highly ionized neon and neon/argon plasmas were produced. We will discuss the experimental set up, measurements details and the modeling and interpretation of the data. |
Wednesday, November 10, 2021 2:48PM - 3:00PM |
PO03.00005: X-ray Heating and Temperature in Multielement Laboratory Photoionized Plasmas Georges S Jaar, Roberto C Mancini, Tom E Lockard, Daniel C Mayes, Ian M Hall, Guillaume P Loisel, James E Bailey, Duane A Liedahl Photoionized plasmas in the universe consist of multiple elements. The mixture of elements is dominated by hydrogen while other elements are present in smaller concentrations. Yet, the heavy elements play a critical role in the dynamics and observations of these astrophysical plasmas. We present modeling and experimental results for neon-hydrogen laboratory photoionized plasmas in which the composition is dominated by hydrogen. The simulations predict that a small amount of neon has a dramatic effect on the x-ray heating of the plasma as is evidenced by the electron temperature. The experiments were performed at the Z facility of Sandia National Laboratories where a gas cell filled with neon and hydrogen was driven by the broadband x-ray flux produced by a wire array z-pinch implosion. The x-ray flux was employed in two different ways. First, to produce and sustain the photoionized plasma. Second, as a backlight for transmission spectroscopy used to diagnose the charge state distribution and extract the electron temperature from a Li-like neon population ratio. We discuss the temperature obtained from a series of experiments for multiple concentration ratios of neon and hydrogen and interpret the results with the aid of radiation-hydrodynamic simulations. |
Wednesday, November 10, 2021 3:00PM - 3:12PM |
PO03.00006: Investigating High Density Accretion Disk Models with Photoionized Iron and Calcium Plasma Experiments Patricia B Cho, Guillaume P Loisel, Taisuke Nagayama, James E Bailey Astrophysical models of black hole accretion disks suggest high Iron abundances in multiple systems that are often many times the Iron abundance in the Sun. This phenomenon is known as the Supersolar Iron Abundance Problem. Historically, these models imposed an upper bound on the plasma density in the accretion disk which is lower than what recent observations suggest. This low density limit was suspected to be a large part of the reason for many of the supersolar Iron abundance determinations. Recently, high density effects have been incorporated in one astrophysical photoionized plasma model known as XSTAR. The effects have significantly revised Iron abundances to lower values for many systems. However, the physical assumptions for these effects have not previously been tested against laboratory data. Photoionized Iron and Calcium plasma experiments have been performed at parameter using the Z-machine at Sandia National Laboratories. Emission data were recorded using an expanded foil sample driven by the high x-ray flux of the Z-pinch. We will describe our motivations, experiment, and the data collected. We will also discuss the data's potential to assess the validity of the physical assumptions relevant to the new high density effects in XSTAR. |
Wednesday, November 10, 2021 3:12PM - 3:24PM |
PO03.00007: Transforming opacity science on Z using novel time-resolved spectroscopy Guillaume P Loisel, James E Bailey, Taisuke Nagayama, Greg Dunham, Gregory A Rochau, Paul Gard, Anthony P Colombo, Aaron Edens, Quinn Looker, Mark W Kimmel, Robert R Speas, John L Porter Models for the Sun and stars remain uncertain today because opacity models are unable to reproduce previous iron opacity measurements at stellar interior conditions [1,2]. Time-resolved spectroscopy using a novel hCMOS Ultra-fast X-ray Imager (UXI, [3,4]) is transforming stellar interior opacity measurements at the Sandia Z facility. First, we can directly measure whether temporal gradients affected the published results. Prior data recorded on x-ray film had duration given by the 3-ns backlighter and one hypothesis for the opacity model data discrepancy is that temporal integration influenced the results. Second, this technology can eventually enable time-resolved Fe opacity measurements. This can not only provide Fe opacities at multiple conditions from a single experiment but can also test Fe-opacity models at more extreme conditions. Third, sample conditions evolution measurements have revealed Fe-opacity samples evolve differently from simulations and the refined understanding has provided insight into how to reach more extreme opacity experiment conditions. We will discuss if the model-data discrepancies are explained by the measured gradient. We will discuss the remaining challenges and our strategy to obtain the first time-resolved opacity measurements on Z. |
Wednesday, November 10, 2021 3:24PM - 3:36PM |
PO03.00008: Oxygen opacity experiments for stellar interiors James E Bailey, Guillaume P Loisel, Taisuke Nagayama, Daniel C Mayes, Greg Dunham, Stephanie B Hansen, Thomas A Gomez, Haibo Huang, Carlos Monton, Don E Winget, Michael H Montgomery, Robert F Heeter, Theodore S Perry, James P Colgan, David P Kilcrease, Chris J Fontes, Christophe Blancard, Gerald Faussurier, Philippe Cosse, Jean-Christophe Pain, Franck Gilleron Testing oxygen opacity calculations is important for understanding the Sun and white dwarf stars. Near the solar convection zone base, Te~ 180 eV, ne ~ 9e22 electrons/cc, and oxygen is mostly H-like or fully-stripped. Highly-ionized oxygen produces a relatively simple opacity spectrum, but its calculation relies on untested approximations for continuum lowering and line broadening. We measured oxygen opacity in multiple Z experiments using SiO2 samples. The Si K-shell spectrum is less perturbed by density effects and provides plasma diagnostic information. Preliminary inferred plasma conditions were Te = 160 eV and ne = 8x1021 cm-3. The 5-19 Angstrom spectral range includes the critical oxygen bound-free absorption, the Ly beta transition, and the opacity window region on the short wavelength side of the Ly alpha line. Experimental results, reproducibility, and initial comparisons with opacity model calculations will be discussed. |
Wednesday, November 10, 2021 3:36PM - 3:48PM |
PO03.00009: All-Order Full-Coulomb Quantum Spectral Line Shape Calculations Thomas A Gomez, Taisuke Nagayama, Patricia B Cho, Mark C Zammit, Chris J Fontes, David P Kilcrease, Igor Bray, Ivan Hubeny, Bart H Dunlap, Michael H Montgomery, Don E Winget Understanding how atoms interact with hot dense matter (HDM) is essential for astrophysical and laboratory plasmas modeling and analysis. In high density plasmas, spectral lines are significantly pressure broadened. Line shape calculations and measurements thus provide a rare window that lets us examine how atoms interact in dense plasmas, for example inside stars. |
Wednesday, November 10, 2021 3:48PM - 4:00PM |
PO03.00010: Re-analysis of plasma temperature and density for stellar iron opacity experiments Taisuke Nagayama, James E Bailey, Guillaume P Loisel, Greg Dunham, Thomas A Gomez, Daniel C Mayes Iron opacities measured at stellar interior conditions were significantly higher than calculated [Bailey, Nature 517, 56 (2015)]. While this helps resolve a decade old solar problem, the question remains: What is responsible for the model-data discrepancy? One recurring question is the accuracy of plasma temperature and density. Accurate determination of plasma conditions are challenging due to multiple sources of uncertainties such as uncertainties due to spectral-line-broadening model, background subtraction, areal density, and analysis method itself. Specifically, uncertainty in the line-broadening models was raised as a serious concern [Nagayama HEDP 2016, Iglesias HEDP 2016]. Recently, the line-shape theory was refined by removing three common approximations. The background determination methods were also improved. Here, we reanalyze the temperature and density of the iron opacity data using the latest line-broadening model and the background determination methods. We also discuss the trade offs between an analysis strategy that infers all desired plasma parameters from the entire spectrum at once and an alternative strategy that infers one plasma parameter at a time using only the spectral features that provide the most sensitivity to the individual parameters. We will summarize the changes in the inferred conditions and its impact on the reported model-data opacity discrepancies. |
Wednesday, November 10, 2021 4:00PM - 4:12PM |
PO03.00011: Temperature and density measurements from stellar interior oxygen opacity experiments using K-shell spectroscopy Daniel C Mayes, James E Bailey, Taisuke Nagayama, Guillaume P Loisel, Greg Dunham, Stephanie B Hansen, Thomas A Gomez, Don E Winget, Michael H Montgomery, Theodore S Perry, Robert F Heeter, Kathy Opachich, Harry F Robey, David P Kilcrease, Chris J Fontes, James P Colgan Our understanding of material opacities in stellar interiors is under scrutiny. Oxygen is among the important contributors to opacity near the base of the solar convection zone. Remarkably, the conditions in this region (180eV, 1e23 e/cc) are similar to some white dwarf stars. The experimental platforms at Z and NIF previously used to study iron opacities also allow for the study of oxygen at these conditions. Measurements of the oxygen opacity have been carried out using SiO2 samples on each platform. For proper comparison of the experimental oxygen opacities with theoretical models, the conditions of the experimental plasma must be well known. In this talk, we will be discussing the methods used to measure the temperature and density of the samples via Si K-shell absorption spectroscopy. |
Wednesday, November 10, 2021 4:12PM - 4:24PM |
PO03.00012: Increasing the accuracy of cold Fe opacity measurements to help resolve the solar Fe opacity puzzle Malia Kao, Guillaume P Loisel, James E Bailey, Patrick Lake, Paul Gard, Gregory A Rochau, George Burns, Barney L Doyle, William R Wampler, Haibo Huang, Michael Weir Iron opacity at electron densities and temperatures similar to solar interior conditions was obtained using the Z machine at Sandia National Laboratories. It was found to be 30-400% higher than what is used in standard solar models. In contrast, it is expected that opacity near solar conditions should be lower than the mass attenuation coefficients of x-ray radiation at room temperature (cold opacity). The caveat is that experimental values for opacity at room temperature are reported to within 10% error at best. The present project attempts to reduce these errors. Cold opacity is determined here using transmission measurements of an iron foil at three different characteristic line energies in the soft x-ray 6-13 Å range. Initial transmission measurements have shown that a few percent error on transmission can be achieved. The required areal density is independently measured by two methods: Rutherford Backscattering Spectroscopy using an ion beamline and an AutoEdge technique using 3-17 keV x-ray transmission over a continuous photon energy range. |
Wednesday, November 10, 2021 4:24PM - 4:36PM |
PO03.00013: Laboratory Generated Photoionization Fronts Relevant to Cosmology Michael Springstead, Heath J LeFevre, Taisuke Nagayama, Guillaume P Loisel, James E Bailey, Sallee Klein, Roberto C Mancini, Kyle J Swanson, Don E Winget, Bart H Dunlap, Joshua S Davis, William J Gray, R P Drake, Carolyn C Kuranz Photoionization Fronts (commonly referred to as Ionization Fronts or PI fronts) are a type of radiation-driven heat front that dictate important physics in reionization era of the early universe. The first galaxies of the reionization era merged to form minihalos. Subsequently, these minihalos emitted ionizing radiation to the surrounding gas clouds, which generated PI fronts. The propagation and attenuation of a PI front within a gas cloud is an active area of study in early universe cosmology. In the laboratory setting, the Z Astrophysical Plasma Properties (ZAPP) platform on Sandia’s Z-Machine facility can generate an intense radiation source to drive a PI front through a 0.75atm nitrogen gas cell. To initially characterize the PI fronts, the speed and electron temperature of the PI front will be measured using photon-doppler velocimetry and streaked visible spectroscopy respectively. This work presents an initial experimental design accompanied by HELIOS radiation-hydrodynamic simulations, and PrismSPECT atomic kinetics calculations to better understand upcoming ZAPP experiments on Sandia’s Z-Machine. |
Wednesday, November 10, 2021 4:36PM - 4:48PM |
PO03.00014: Laboratory photoionized plasmas in steady state Roberto C Mancini, Ryan P Schoenfeld, Jeffrey Rowland, Robert F Heeter, Duane A Liedahl, Sean P Regan Performing laboratory photoionized plasma experiments that achieve steady state is a standing challenge. This is important for testing physics models employed in the interpretation of x-ray astronomy observations. A new platform has been established at the OMEGA EP laser facility in which a tamped silicon sample is driven by a three-Cu hohlraum x-ray source that produces a 30ns-duration, broadband x-ray flux with a radiation temperature of 90eV. The long duration x-ray flux is critical for producing a photoionized plasma in steady-state in the laboratory. The x-ray source performance is monitored with VISAR and its spectral distribution is recorded with a grating spectrometer. The silicon plasma is diagnosed with K-shell absorption spectroscopy. The latter is afforded by using a laser beam to drive a separate 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 will discuss modeling simulations done to design the experiment and the observations recorded during a series of campaigns at OMEGA EP. This work is supported by DOE NNSA NLUF Grant DE-NA0003936. |
Wednesday, November 10, 2021 4:48PM - 5:00PM |
PO03.00015: Absorption Spectroscopy in Photoionization Front Laboratory Experiments Kwyntero V Kelso, Heath J LeFevre, Sallee Klein, Paul A Keiter, William J Gray, Joshua S Davis, R P Drake, Carolyn C Kuranz |
Follow Us |
Engage
Become an APS Member |
My APS
Renew Membership |
Information for |
About APSThe American Physical Society (APS) is a non-profit membership organization working to advance the knowledge of physics. |
© 2024 American Physical Society
| All rights reserved | Terms of Use
| Contact Us
Headquarters
1 Physics Ellipse, College Park, MD 20740-3844
(301) 209-3200
Editorial Office
100 Motor Pkwy, Suite 110, Hauppauge, NY 11788
(631) 591-4000
Office of Public Affairs
529 14th St NW, Suite 1050, Washington, D.C. 20045-2001
(202) 662-8700