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 BI02: High Energy Density PlasmaLive Streamed
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Chair: Charles Starrett, LANL Room: Ballroom 100 B |
Monday, October 17, 2022 9:30AM - 10:00AM |
BI02.00001: The Compressibility of Shocked Hydrogen up to 1 TPa Invited Speaker: J. Ryan Rygg Warm dense hydrogen near 1 TPa (1 TPa = 10 million atm) sits at a confluence of energy scales, where the thermal energy, Fermi energy, Coulomb coupling energy, and plasma oscillation energy are simultaneously in the vicinity of the free-hydrogen ionization energy of 1 Ry = 13.6 eV. Recent Hugoniot and sound speed experiments on single- and double-shocked liquid deuterium[1],[2] provide evidence for increased compression of hydrogen compared to all theoretical models in this regime. We show that a specific heat contribution from plasma waves, not explicitly included in the theoretical models, is sufficient to explain the compressibility discrepancy. This model will be compared to recent experimental results obtained at the National Ignition Facility for deuterium shocked and reshocked above 1 TPa and 2 TPa, respectively. This material is based upon work supported by the Department of Energy National Nuclear Security Administration under Award Number DE-NA0003856. [1] A. Fernandez-Pañella et al., Phys. Rev. Lett. 122, 255702 (2019).
[2] D. E. Fratanduono et al., Phys. Plasmas 26, 012710 (2019).
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Monday, October 17, 2022 10:00AM - 10:30AM |
BI02.00002: Measuring the Melting Curve of Iron at Super-Earth Core Conditions Invited Speaker: Richard G Kraus The discovery of over 4500 extra-solar planets has created a need for modelling their interior structure and dynamics. The prominence of iron in planetary interiors requires accurate and precise physical properties at extreme pressure and temperature. A first-order property of iron is the melting point, which is still debated for the conditions of Earth’s interior. We used high-energy lasers at the National Ignition Facility and in-situ x-ray diffraction to determine the melting point of iron up to 1000 GPa, three times the pressure of Earth’s inner core. We used our observation to determine the length of dynamo action during core solidification to the hexagonal close-packed structure. We find that terrestrial exoplanets with four to six times Earth’s mass have the longest dynamos, which provide important shielding against cosmic radiation. |
Monday, October 17, 2022 10:30AM - 11:00AM |
BI02.00003: Transforming the opacity science on Z using novel time-resolved spectroscopy Invited Speaker: Guillaume P Loisel Time-resolved spectroscopy using a novel Ultra-fast X-ray Imager (UXI) is transforming stellar interior opacity measurements at the Sandia Z facility. Models for the Sun and stars are uncertain because opacity models are unable to reproduce previous iron opacity measurements at stellar conditions [1,2]. The unprecedented new data help resolve this dilemma in three important ways. First, prior opacity data recorded on x-ray film had duration given by the 3-ns backlighter. One hypothesis for the opacity model-data discrepancy is that the temporal integration influenced the results. Time-resolved data directly test this hypothesis. Second, Sandia’s UXI technology [3,4] enables measurements of iron opacities at multiple conditions from a single experiment. This increases the learning rate since fewer experiments are needed to test the model predictions for trends in opacity changes with plasma conditions. Third, measurements of the iron sample temperature and density evolution refine the experimental understanding. Better understanding enables improved experimental design. For example, both the measured temperature and the density of the iron opacity sample increase with time. This contradicts expectations based on simulations and provides insight into how to reach more extreme experimental conditions. We will discuss the first results from experiments designed to take advantage of newly acquired time-resolved knowledge to tailor the opacity experimental conditions. Obtaining the first time-resolved absolute opacity data on Z is in progress. The strategy and prospects for obtaining multiple opacity measurements from a single Z experiment will be discussed. |
Monday, October 17, 2022 11:00AM - 11:30AM |
BI02.00004: Experimental Observations of Laser-Driven Tin Ejecta Microjet Interactions Invited Speaker: Alison Saunders The study of high-velocity particle-laden flow interactions is broadly applicable to fields ranging from planetary formation to cloud interaction dynamics. Ejecta microjets offer a novel experimental methodology to study such interactions, as microjets consist of micron-scale particles that travel at velocities greater than several kilometers per second. At such velocities, collisions between particles can cause break-up or conglomeration and can impart enough energy to alter the material state through melting or vaporization. As such, interaction behavior of high-velocity particle flows is difficult to predict and requires experimental data to benchmark collisional models. Ejecta microjets are generated when a strong shock releases from a surface with a feature, such as a groove or a divot; the feature then inverts as a limiting case of the Richtmyer-Meshkov Instability and forms a propagating jet of material. We present on experiments performed at the OMEGA EP laser facility that observed the interaction of two counter-propagating tin ejecta microjets for the first time through x-ray radiography imaging [1]. We observe that jets emerging from a shock pressure of 11.7 GPa pass through each other unattenuated, whereas jets emerging from a shock pressure of 116.0 GPa have five times greater densities and interact strongly, forming a cloud around the center-point of interaction. Radiation hydrodynamics simulations of particle-stream collisions capture many of the observed interaction characteristics but are unable to capture the full spread of the cloud formed, suggesting that more work is needed to understand the physics dominating collisional behavior of ejecta microjets. |
Monday, October 17, 2022 11:30AM - 12:00PM |
BI02.00005: Proton stopping power measurements in warm dense matter at low velocity projectile ratio Invited Speaker: Sophia Malko Ion stopping power in high energy density (HED) plasmas is of great interest for fundamental science and is important in many areas of inertial confinement fusion, including central hot spot ignition, fast ignition, and heavy ion fusion. Theoretical modelling of ion stopping power in HED plasmas is a difficult task and there is little experimental data to validate and benchmark models, contributing to large discrepancies amongst them. The modelling of stopping power in Warm Dense Matter (WDM) is particularly challenging due to electron degeneracy and coupling, which modify the Coulomb logarithm characterizing the collisions in the plasma. While a number of experimental studies have been performed on ion stopping power in classical plasmas, experimental database in WDM is essentially missing. In addition, the low velocity stopping power regime where vp (ion velocity) ~ vth (electron thermal velocity) remains virtually unexplored. |
Monday, October 17, 2022 12:00PM - 12:30PM |
BI02.00006: New Perspectives for the ab-initio Simulation and Diagnostics of Warm Dense Matter Invited Speaker: Tobias Dornheim Warm dense matter (WDM), an extreme state that is characterized by extreme densities and temperatures, has emerged as one of the most active frontiers in plasma physics and material science. In nature, WDM occurs in astrophysical objects such as giant planet interiors and brown dwarfs. In addition, WDM is highly important for technological applications such as inertial confinement fusion and the discovery of novel materials. |
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