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 BO06: High-Z, Multiply Ionized Atomic PhysicsLive Streamed
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Chair: Mark Zammit, LANL Room: Ballroom 111 C |
Monday, October 17, 2022 9:30AM - 9:42AM |
BO06.00001: Extreme Atomic Physics in Plasma Mixtures at Gbar Pressure Suxing Hu, D. T Bishel, D. A Chin, Philip M Nilson, Valentin V Karasiev, Igor E Golovkin, M. Gu, Stephanie B Hansen, Deyan I Mihaylov, Nathaniel R Shaffer, Shuai Zhang, Timothy Walton Observable changes in atomic spectra at very high pressures offer a test of our fundamental understanding of matter in extreme conditions -- and by extension the spectroscopic interpretation of dense astrophysical objects. However, detailed spectroscopic data at pressures comparable to stellar interior conditions are rare, severely limiting the information available to guide the development of atomic and plasma physics models. In this talk, we report both time-integrated and time-resolved x-ray spectroscopy data at several billion atmospheres (~Gbar) with a laser-driven spherical implosion. Using a Cu-doped layer located inside a stagnating plastic shell, detailed Cu Kα-emission and 1s-2p absorption spectra are measured in CH-Cu plasma mixtures. The spectral observations, augmented by experimentally constrained radiation-hydrodynamic predictions of the imploded plasma conditions, are in good agreement with a self-consistent treatment of the dense-plasma environment based on density-functional theory (DFT). Compared to the DFT-based approach, the similarities and differences of a traditional collisional-radiative equilibrium (CRE) treatment, which uses an isolated atomic database with ad hoc continuum lowering models, are revealed. These results open a path towards developing a deeper understanding of dense-plasma mixtures at ultra-high pressure. |
Monday, October 17, 2022 9:42AM - 9:54AM |
BO06.00002: Measurements of Au Ionization Using L- and M-shell X-ray Emission Edward V Marley, Christine M Krauland, Marilyn B Schneider, Duane A Liedahl, Gregory E Kemp, Mark E Foord, Robert F Heeter An experiment has been done at the NIF using a buried layer platform to study the radiative properties of non-local thermodynamic equilibrium (NLTE) gold plasma at an electron temperature of ∼3 keV and an electron density of ∼1021cm-3. The targets used consisted of a 625 μm diameter, 1900 Å, thick dot with a 1:2.25 atomic mix of gold and zinc in the center of a 2500 μm diameter, 10 μm thick beryllium tamper. Lasers heat the target from both sides for 4.0 ns. The size of the emitting volume vs time was measured side-on with x-ray imaging. The radiant x-ray power was measured with a low-resolution, absolutely calibrated x-ray spectrometer (DANTE). The Au L-shell and the Zn K-shell were measured simultaneously and time resolved with the same spectrometer and streak camera. A second spectrometer/streak camera was used to measure the M-shell emission of the Au. The electron temperature was inferred from the measured zinc K-shell emission. The ionization balance of the gold is inferred from the measured L- and M-shell emission of the gold. A comparison is made between the sensitivity of the K- and L-shell emission to conditions of the thermal plasma. |
Monday, October 17, 2022 9:54AM - 10:06AM |
BO06.00003: Exploring variations in dynamic collision frequencies Stephanie B Hansen, Thomas Hentschel, Alina Kononov, Andrew D Baczewski In a steady (zero-frequency) electric field, electron-ion collision frequencies inform the conductivity of materials and line shapes in the warm and hot dense matter regimes. Oscillating fields introduce dynamic effects that modify the collision frequencies, affecting absorption and scattering signatures of plasmas. Here, we explore how changes to scattering cross sections, densities of states, ion structure factors, integration methods, and inelastic processes modify the dynamic collision frequencies and associated observables such as the damping of plasmons in X-ray Thomson Scattering spectra. |
Monday, October 17, 2022 10:06AM - 10:18AM |
BO06.00004: Statistical inference of electron-ion collision rates from simulated X-ray Thomson scattering spectra Thomas Hentschel, Alina Kononov, Andrew D Baczewski, Stephanie B Hansen
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Monday, October 17, 2022 10:18AM - 10:30AM |
BO06.00005: A methodology to constrain continuum lowering models at high energy densities David T Bishel, Philip M Nilson, David A Chin, John J Ruby, Suxing Hu, Ethan Smith, Reuben Epstein, Igor E Golovkin, J. Ryan Rygg, Gilbert W Collins Continuum lowering models describe the response of an ion to the high-density environments typical of astrophysical objects and fusion plasmas. Recent measurements have challenged these traditional models, signaling the need for modern descriptions of dense plasmas. Future experiments must discriminate between competing models to guide the development of theory. In this talk, a methodology is developed to constrain continuum lowering models. Synthetic Cr K-shell spectra are generated and analyzed with a parametrized solution to the equation of radiative transfer. Different continuum lowering models are used to analyze the synthetic spectra. The geometric and thermodynamic parameters most consistent with the synthetic spectra are used to define the required accuracy of experimental measurements. This quantitative methodology is guiding the design of thick-shell implosion experiments hosting a Cr layer to study atomic physics at high energy densities. |
Monday, October 17, 2022 10:30AM - 10:42AM |
BO06.00006: Atomic and radiative processes in X-Ray driven plasma ablation experiments performed on the MAGPIE pulsed-power generator Jack W Halliday, Aidan C Crilly, Jeremy P Chittenden, Roberto C Mancini, Stefano Merlini, Steven J Rose, Danny R Russell, Jergus Strucka, Vicente Valenzuela-Villaseca, Simon N Bland, Sergey V Lebedev We present results from a novel experimental platform [1] in which the x-rays from a wire array Z-pinch are used to irradiate a silicon target, producing an outflow of ablated plasma. The plasma expands into ambient B-fields (∼5 T). The outflows have a well-defined (quasi-1D) morphology, enabling the study of fundamental processes typically only accessible in more integrated experiments. |
Monday, October 17, 2022 10:42AM - 10:54AM |
BO06.00007: Simulations of Collisional Effects in an Inner-Shell Mg Solid-Density X-Ray Laser Shenyuan Ren, Sam M Vinko, Justin Wark Inner-shell K-alpha x-ray lasers have previously been created by pumping with the intense x-ray output of free-electron-lasers (FELs) - this first being demonstrated in a Neon gas [1] and subsequently in solid materials [2,3]. Lasing relies on the creation of core-holes on a time-scale short compared with filling via Auger decay. In the case of solid density systems, collisional effects will also be important, yet to date such effects have not been extensively studied. We present here simulations using the CCFLY code of inner-shell lasing in solid density Mg, where we self-consistently treat the effects of the incoming FEL radiation and the atomic kinetics of the Mg system, including radiative, Auger, and collisional effects. We find that collisional depopulation of higher ionisation stages precludes lasing on all but the K-alpha of the neutral system. |
Monday, October 17, 2022 10:54AM - 11:06AM |
BO06.00008: Probing transient multi-center ionic structures in hot dense plasmas Jean Clerouin, augustin Blanchet
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Monday, October 17, 2022 11:06AM - 11:18AM |
BO06.00009: Monte Carlo Radiation Transport Simulation of Nonthermal X-ray Fluorescence in a MagLIF Plasma Ryan R Childers, Stephanie B Hansen, Alla S Safronova, David J Ampleford Nonthermal radiation is essential for the characterization of high-energy-density plasma environments, wherein production and transport mechanisms driving this radiation are often complex and characterized by non-LTE conditions. These processes can be studied using computational methods like Monte Carlo random walk techniques, which are effective in simulating deterministic particle interaction through randomization and probabilistic selection. In this work, radiation transport is simulated in a laboratory MagLIF plasma using a newly constructed Monte Carlo Radiation Transport code. The code simulates a central Te ~ 4 keV, r ~100 μm thermal core which irradiates the surrounding r ~ 500 μm liner medium (Be & 114 ppm Fe). Atomic processes are calculated using a newly developed screened-hydrogenic atomic code. Characteristics such as Fe <Z>, average Te, and K- and L-shell yields are tracked and calculated. Simulation includes radial temperature distribution fueled by deposition of nonthermal and thermal core photons, emergent transmission spectrum with escaped nonthermal Fe Kα & Kβ intensities, and spatial statistics of their production, revealing a dense region of production ~150 mm from the thermal core. Comparison of simulated Fe fluorescence to experimental data is provided. |
Monday, October 17, 2022 11:18AM - 11:30AM |
BO06.00010: New capabilities with the short-pulse laser system of the MEC instrument at LCLS Dimitri Khaghani, Eric Galtier, Meriame Berboucha, Eric Cunningham, Gilliss Dyer, Phil Heimann, Hae Ja Lee, Bob Nagler, Hai-En Tsai, Michael Greenberg We report on the recent upgrade of the MEC instrument at the LCLS x-ray free electron laser improving the beam delivery of the short-pulse laser system. New optomechanics platforms have been designed and commissioned to guarantee a faster and more reliable setup of the short-pulse laser beam. These are part of the new standard beam delivery configurations offered at MEC in conjunction with the FEL beam. A low-energy configuration is available with 10 mJ in 50 fs at 400 nm. An uncompressed configuration was also carried out with 1.5 J in 150 ps at 800 nm. Finally, a high-intensity configuration is offered with 1 J in 50 fs at both 800 and 400 nm, available at different incidence angles from 22˚ to 59˚. We will present the technical performances of these beam delivery configurations in terms of pointing stability, spatial and temporal overlap with the x-ray beam and wave-front profile. We will also highlight recent scientific results obtained with these platforms that support broad fields of physics enabled with these new features at MEC. |
Monday, October 17, 2022 11:30AM - 11:42AM |
BO06.00011: Hard X-ray emission and scattering spectrometers for dense plasma studies at MEC, LCLS Haeja Lee, Eric Galtier, Dimitri Khaghani, Eric Cunningham, Hai-En Tsai, Nina Boiadjieva, Philip Hart, Peregrine McGehee, Brice Arnold, Philip Heimann, Bob Nagler, Gilliss Dyer X-ray spectroscopy with an ultrabright, tunable XFEL source is a powerful diagnostic for characterization of fundamental properties such as electronic structure, temperature, and density of high energy density plasma. We have built two spectrometers for X-ray emission and scattering studies in the hard X-ray photon energy range between 7 keV and 25 keV. One uses a Highly Annealed Pyrolytic Graphite crystal in von Hamos geometry while the other uses an asymmetric plane of a Quartz crystal in Cauchois geometry. The commissioning experiment utilizes the LCLS hard X-ray FEL beam and the short pulse optical laser system of the MEC instrument to measure resolution performances via emission lines and Compton feature. In this talk, the details of the two spectrometers and preliminary commissioning results will be presented with a discussion of dense plasma conditions. |
Monday, October 17, 2022 11:42AM - 11:54AM |
BO06.00012: X-Ray Absorption Fine Structure Spectroscopy of Iron Compounds at High-Energy-Density Conditions David A Chin, Philip M Nilson, David T Bishel, Mary Kate Ginnane, Xuchen Gong, Suxing Hu, Brian Henderson, Reetam Paul, Danae Polsin, Ethan Smith, J. Ryan Rygg, Gilbert W Collins, John J Ruby, Amy L Coleman, Federica Coppari, Yuan Ping, Marion Harmand, Raffaella Torchio, Alexis Amouretti A critical next step in understanding high-energy-density (HED) matter is to characterize both the temperature and chemistry of materials at HED conditions. Temperature measurements are historically difficult at low temperature HED conditions above 100 GPa and below 5000 K. Furthermore, when we compress matter to these extreme conditions, electron orbitals can be distorted leading to new chemistry. X-ray absorption fine structure spectroscopy is a unique technique capable of simultaneously constraining in situ both the temperature and chemistry of compressed materials. At the Omega Laser Facility, multiple iron compounds were quasi-ramp compressed to above 500 GPa and probed with a broadband x-ray source. A new x-ray spectrometer with improved spectral resolution and energy calibration was used to measure the x-ray absorption spectrum. This improved resolution allowed x-ray absorption near edge spectroscopy features of Fe2O3 to be measured and these data indicate continued electron orbital distortion with increasing pressure. Moreover, the modulations in the extended x-ray absorption fine structure region of the spectrum were fit using a FEFF[1]-based Bayesian inference routine to characterize the ion positions and ultimately the temperature through analytical models of the phonon spectrum and lattice potential wells. [1] J. J. Rehr et al., Phys. Chem. Chem. Phys. 12, 5503 (2010).
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