Tilo Doeppner | 18-ERD-033
Project Overview
In high-density plasmas the atomic-bound states are modified due to screening by free electrons and the interaction with neighboring ions such that ionization energies are lowered compared to an isolated atom. Correctly modeling these effects is crucial for understanding high-energy-density (HED) matter as the ionization balance in a plasma determines many important properties like heat capacity, opacity, and compressibility. An accurate understanding of these plasma properties at ultra-high densities is of direct relevance to inertial confinement fusion (ICF), where such densities are reached in the ablator close to stagnation.
In experiments conducted at Lawrence Livermore National Laboratory's National Ignition Facility (NIF), we measured the ionization in low-Z materials—such as beryllium, plastic (CH), and high-density carbon (HDC)—at unprecedented electron and mass densities on order of 40 grams per cubic centimeter (g/cc) using x-ray Thomson scattering (XRTS). Under these extreme conditions, where high electron degeneracy is present, the plasma pressure exceeds 1 gigabar. To date, no other ionization measurement exists in this parameter regime, and currently NIF is the only facility worldwide where XRTS measurements at such extreme compressions can be made. In general, we measured significantly increased ionization compared to predictions from widely used ionization models like Stewart & Pyatt, indicating that commonly used models underpredict the ionization potential depression (IPD) in plasmas at extreme densities. Additionally, we developed new experimental platforms for NIF that allow forward XRTS with sensitivity to collective electron oscillations (plasmons) and simultaneous radiography and radiography measurements for high-precision equation-of-state (EOS) measurements at tens of megabars.
The experimental measurements conducted during this project provide important benchmarks for modeling HED plasmas. Our results support new theoretical work on improving modeling of IPD beyond Stewart & Pyatt, both inside and outside of the Laboratory, specifically work regarding how correlation and degeneracy effects in such strongly coupled systems need to be considered. In this way, the project has made important contributions for an improved understanding of ionization and opacity in dense plasmas at gigabar pressures, at conditions relevant to ICF capsule implosions near stagnation.
Mission Impact
This research enhances Livermore's core competency in HED science, including research related to ICF. An accurate knowledge of the ionization balance in ultra-dense plasmas is crucial to further improve EOS tables, which affect many thermodynamic and transport properties. In addition, such knowledge is of instrumental importance to further improve predictability in plasma modeling in the Laboratory's mission research challenge in nuclear weapons science.
Publications, Presentations, and Patents
Allen, C. H. et al. 2019. "Collective X-ray Thomson Scattering Measurements from Beryllium Capsule Implosions at the National Ignition Facility." Presentation to Summer Student Working Group, Lawrence Livermore National Laboratory, Livermore, CA, August 2019. LLNL-PRES-787652
Bethkenhagen, M. et al. 2020, "Carbon ionization at gigabar pressures: An ab initio perspective on astrophysical high-density plasmas." Phys. Rev. Research, 2: 023260, doi:10.1103/PhysRevResearch.2.023260. LLNL-JRNL-800319
Bishel, D. T., et al. 2018. "Using time-resolved penumbral imaging to measure low hot spot x-ray emission signals from capsule implosions at the National Ignition Facility." Rev. Scient. Instrum. 89: 10G111. doi:10.1063/1.5037073. LLNL-JRNL-751761
Böhme, M., et al. 2018. "Analyzing XRTS spectra from beryllium capsule implosions at the NIF." 6th High-Power Laser Workshop, SLAC National Accelerator Laboratory, Palo Alto, CA, September 2018. LLNL-POST- 867827
——— 2019. "X-ray Thomson scattering from imploding capsules at the NIF." NIF User group meeting, Livermore, CA, February 2019. LLNL-POST-766690
Döppner, T., et al. 2017. "Using X-ray Thomson Scattering to Characterize Highly Compressed, Near-Degenerate Plasmas at the NIF." 59th Annual Meeting of the APS Division of Plasma Physics, Milwaukee, MN, October 2017. LLNL-PRES-740025
——— 2018a."X-ray Scattering Measurements from 30-fold Compressed, Near-Degenerate Plasmas at the National Ignition Facility." 2018 International Workshop on Radiative Properties of Hot Dense Matter, Hamburg, Germany, October 2018. LLNL-POST-760038
——— 2018b."X-ray Thomson scattering experiments at the National Ignition Facility (NIF)." Institute Seminar at Helmholtz-Zentrum Dresden-Rossendorf (HZDR) Dresden, Germany, June 2018. LLNL-PRES-753063
——— 2018c. "X-ray Thomson scattering experiments at the National Ignition Facility (NIF)." Special Colloquium at University of Rostock, Rostock, Germany, June 2018. LLNL-PRES-753063
——— 2018d. "Role of Ionic Screening in Pressure Ionization in Dense Plasmas." Invited talk, NIF User group meeting, Livermore, CA, February 2018. LLNL-PRES-745797
——— 2019a. "X-ray scattering measurements from 30-fold compressed, near-degenerate plasmas at the National Ignition Facility." 11th International Conference on Inertial Fusion Sciences and Applications, Osaka, Japan, September 2019. LLNL-PRES-790166
——— 2019b. "X-ray scattering measurements from 30-fold compressed, near-degenerate plasmas at the National Ignition Facility." International Workshop for HED Physics, Rostock, Germany, July 2019. LLNL-PRES-781240
——— 2019c. "X-ray Scattering Measurements from 30-fold Compressed, Near-Degenerate Plasmas at the National Ignition Facility." 10th International Workshop on Warm-Dense-Matter 2019, Travemuende, Germany, May 2019. LLNL-POST-760038
——— 2019d. "X-ray Scattering Measurements from 30-fold Compressed, Near-Degenerate Plasmas at the National Ignition Facility." NIF User group meeting, Livermore, CA, February 2019. LLNL-POST-760038
——— 2020. "X-ray Scattering Measurements from 30-fold Compressed, Near-Degenerate Plasmas at the National Ignition Facility." NIF User group meeting, Livermore, CA, February 2020. LLNL-POST-760038
Kraus, D., et al. 2019. "Characterizing the ionization potential depression in dense carbon plasmas with high-precision spectrally resolved x-ray scattering." Plasma Phys. Control. Fusion 61:014015. doi:10.1088/1361-6587/aadd6c. LLNL-JRNL-757664
LeFevre, H. J., et al. 2018. "A platform for x-ray Thomson scattering measurements of radiation hydrodynamics experiments on the NIF." Rev. Scient. Instrum. 89: 10F105. doi:10.1063/1.5039392. LLNL-JRNL-751761
MacDonald, M. J., et al. 2017. "Spatially Resolved X-ray Fluorescence Spectroscopy of Beryllium Capsule Implosions on the NIF." 59th Annual Meeting of the APS Division of Plasma Physics, Milwaukee, MN, October 2017. LLNL-PRES-740155
——— 2018. "Developing a long-duration Zn K-alpha source for x-ray scattering experiments." Rev. Scient. Instrum. 89:10F109. doi:10.1063/1.5039365. LLNL-JRNL-750935
——— 2019a. "High-precision ionization balance measurements in warm dense matter at the NIF." CMEC review meeting, San Diego, CA, November 2019. LLNL-PRES-796992
——— 2019b. "Using x-ray fluorescence to measure temperature in high-energy-density hydrodynamics experiments." Innovating Diagnostics for High Energy Density Hydrodynamics Experiments, Santa Fe, NM, March 2019. LLNL-PRES-769636
——— 2019c. "High precision equation of state measurements of warm dense matter at the NIF." NIF User group meeting, Livermore, CA, February 2019. LLNL-POST-767165
——— 2020a. "High-precision ionization balance measurements in warm dense matter at the NIF." Monthly Meeting of Center for Matter at Extreme Conditions (online), May 2020. LLNL-PRES-810681
——— 2020b. "High-precision ionization balance measurements in warm dense matter at the NIF." NIF User group meeting, Livermore, CA, February 2020. LLNL-PRES-804278
Röpke, G., et al. 2018. "Ionization potential depression and Pauli blocking in degenerate plasmas at extreme densities." Phys. Rev. E. 99: 033201. doi: 10.1103/PhysRevE.99.033201; IM# LLNL-JRNL-763468
Saunders, A. M., et al., 2017. "X-Ray Thomson Scattering and Radiography from Spherical Implosions on the OMEGA Laser." 59th Annual Meeting of the APS Division of Plasma Physics, Milwaukee, MN, October 2017. LLNL-PRES-740153
——— 2018a. "Influence of argon impurities on the elastic scattering of x-rays from imploding beryllium capsules." High Energy Dens. Phys. 26: 86. doi:10.1016/j.hedp.2018.02.003. LLNL-JRNL-742926
——— 2018b. "Characterizing plasma conditions in radiatively heated solid-density samples with x-ray Thomson scattering." Phys. Rev. E, 98: 063206. doi: 0.1103/PhysRevE.98.063206. LLNL-JRNL-758623
——— 2018c. "X-ray Thomson Scattering from Shock-Compressed Diamond Spheres on the OMEGA Laser." 60th Annual Meeting of the American Physical Society Division of Plasma Physics, Portland, OR, November 2018. LLNL-PRES-760267
——— 2018d. "X-ray Thomson Scattering from Shock-Compressed Diamond Spheres on the OMEGA Lase." Invited talk at European Conference on Laser Interaction with Matter, Rethymno, Crete, Greece, October 2018. LLNL-PRES-760099
——— 2018e. "X-Ray Thomson Scattering and Radiography from Spherical Implosions on the OMEGA Laser." 38th International Workshop on High Energy Density Physics, Hirschegg, Austria, January/February 2018. LLNL-PRES-745661
