Probing High-Energy-Density Matter with X Rays

Wednesday, February 22, 2023 - 3:00pm

SLAC, Virtual Photon Science Seminar & ZOOM LINK

Speaker: Suxing Hu, Laboratory for Laser Energetics (University of Rochester)

Program Description:

Matter under extreme high-energy-density (HED) conditions (e.g., at superhigh pressures from billions to trillions of atmospheres) are often encountered in stars and inertial confinement fusion targets. Such extreme HED matter can now be created on energetic laser/XFEL facilities and pulsed-power machines in laboratories. Accurate knowledge of extreme HED matter is essential to better understanding planetary science and astrophysics, as well as reliably designing fusion energy targets. Over the past decade, research has revealed that traditional plasma-physics models often fail to describe the physics of matter under HED conditions since strong coupling and electron degeneracy play a crucial role in such quantum many-body systems.
Probing HED matters in an experiment mostly relies on x rays since it is one of the possible sources that can penetrate dense matters. X-ray–induced fluorescence and/or absorption are often used to infer what happens inside extreme HED matter. On the theoretical/computational side, ab initio methods such as density functional theory (DFT) and time-dependent DFT [1] can provide a self-consistent way to predict the properties of HED matter (with systematic improvement possible). Combining both x-ray spectroscopy experiments and ab initio calculations, we have investigated some new HED physics phenomena over the past few years, which include the Fermi-surface rising in warm dense matter [2] and interspecies radiative transition in super-dense matter [3]. To understand these precision x-ray spectroscopy measurements, we have derived a DFT-based kinetic model to explore the extreme atomic physics of HED matters at Gbar pressures [4], which enables us to eliminate the controversial continuum-lowering models for dense plasmas. In this talk, I will share what we have learned so far in exploring HED matter, as well as what we are still struggling to understand.
1. Y. H. Ding et al., Phys. Rev. Lett. 121, 145001 (2018).
2. S. X. Hu, Phys. Rev. Lett. 119, 065001 (2017).
3. S. X. Hu et al., Nature Communications 11, 1989 (2020).
4. S. X. Hu et al., Nature Communications 13, 6780 (2022).

Short-Bio (if needed): Dr. Suxing Hu is a Distinguished Scientist and Group Leader of the High-Energy-Density Physics (HEDP) Theory Group at the University of Rochester’s Laboratory for Laser Energetics (LLE). Research in his group has focused on the fundamental understanding of physics properties of matter under extreme conditions encountered in inertial confinement fusion, planetary science, and astrophysics. Suxing started theoretical studies of how an intense and ultrashort laser pulse interacts with atoms, molecules, and clusters in late 1990s. He earned his Ph.D. in physics from the Chinese Academy of Sciences at Shanghai Institute of Optics and Fine Mechanics in 1998. After graduation, he took the Alexander von Humboldt Fellowship and continued his theoretical AMO physics researches at the University of Freiburg and Max-Born Institute in Berlin, Germany. He came to the U.S. as a postdoc research associate at the University of Nebraska-Lincoln and became a Director’s Postdoc Fellow at Los Alamos National Laboratory in 2003. He joined LLE as a Scientist and subsequently became a Senior Scientist in 2013 and a Distinguished Scientist in 2019. As a theoretician, he is interested in understanding how matter behaves under extreme conditions such as under ultrahigh pressures and in super-strong/ultrafast laser fields. Suxing was awarded the Hundred Outstanding Doctorate Thesis Prize by China’s Department of Education, the Alexander von Humboldt Fellowship, and Director’s Postdoc Fellowship at Los Alamos National Laboratory. He has published over ~250 research articles that received over ~8600 citations, with an H-index = 51 by Google-Scholar. For his significant contribution to ultrafast attosecond physics, he was elected a Fellow of the American Physical Society in 2013.

Probing High-Energy-Density Matter with X Rays
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