
The Center invites HED science researchers to deliver presentations as part of our weekly seminar series for LLNL staff, postdocs, and interns.
All presentations are the work of the speakers and owned by their respective institutions. We thank the speakers for permission to post their work here. To watch featured seminars, please visit the Livermore Lab Events YouTube channel.
If you are interested in delivering a seminar, we invite you to contact the Center's Seminar Series Chair, Paul Grabowski, at grabowski5 [at] llnl.gov (grabowski5[at]llnl[dot]gov).
June 29, 2023
Dr. Atilla Cangi
Center for Advanced Systems Understanding
Helmholtz-Zentrum Dresden-Rossendorf (HZDR), Germany
In this talk, I will present two lines of our research. In the first part, I will discuss the application of time-dependent density functional theory (TDDFT) in modeling observables induced in matter under extreme conditions, such as the electron loss function relevant to scattering experiments with X-ray free electron lasers [1] and the electrical conductivity in metals [2]. In the second part, I will highlight our recent progress in leveraging Artificial Intelligence (AI) to enhance the efficiency of electronic structure calculations [3]. Specifically, I will focus on our efforts to accelerate Kohn-Sham density functional theory calculations at finite temperatures by integrating deep neural networks into the Materials Learning Algorithms framework [4,5]. Our results demonstrate significant improvements in calculation speed for metals up to their melting point. Additionally, our implementation of automated machine learning has led to substantial savings in computational resources for identifying optimal neural network architectures, paving the way for large-scale AI-driven investigations [6]. Lastly, I will present our latest breakthrough, showcasing the capability of neural-network-driven electronic structure calculations for systems containing over 100,000 atoms [7].
[1] Z. Moldabekov, T. Dornheim, A. Cangi, Sci. Rep. 12, 1093 (2022).
[2] K. Ramakrishna, M. Lokamani, A. Baczewski, J. Vorberger, A. Cangi, Phys. Rev. B 107, 115131 (2023).
[3] L. Fiedler, K. Shah, M. Bussmann, A. Cangi, Phys. Rev. Materials 6, 040301, (2022).
[4] A. Cangi, J. A. Ellis, L. Fiedler, D. Kotik, N. A. Modine, V. Oles, G. A. Popoola, S. Rajamanickam, S. Schmerler, J. A. Stephens, A. P. Thompson, MALA, https://doi.org/10.5281/zenodo.5557254 (2021).
[5] J. A. Ellis, L. Fiedler, G. A. Popoola, N. A. Modine, J. A. Stephens, A. P. Thompson, A. Cangi, Phys. Rev. B 104, 035120 (2021).
[6] L. Fiedler, N. Hoffmann, P. Mohammed, G. A. Popoola, T. Yovell, V. Oles, J. A. Ellis, S. Rajamanickam, A. Cangi, Mach. Learn.: Sci. Technol. 3, 045008 (2022).
[7] L. Fiedler, N. A. Modine, S. Schmerler, D. J. Vogel, G. A. Popoola, A. P. Thompson, S. Rajamanickam, A. Cangi, Npj Comput. Mater., accepted (2023).
June 22, 2023
Understanding electronic correlations in warm dense quantum plasmas
Dr. Tobias Dornheim
Center for Advanced Systems Understanding (CASUS), D-02826 Görlitz, Germany
Helmholtz-Zentrum Dresden-Rossendorf (HZDR), D-01328 Dresden, Germany
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 cutting-edge technological applications such as inertial confinement fusion and the discovery of novel materials. In the laboratory, WDM is studied experimentally in large facilities around the globe, and new techniques have facilitated unprecedented insights. Yet, the interpretation of these experiments requires a reliable diagnostics based on accurate theoretical modeling, which is a notoriously difficult task [1]. In this work, I will give an overview of how we can use exact ab-initio path integral Monte Carlo (PIMC) simulations [2] together with thermal density functional theory (DFT) calculations to get new insights into the behavior of WDM. Moreover, I will show how switching to the imaginary time representation allows us to significantly improve the interpretation of X-ray Thomson scattering (XRTS) experiments, which are a key diagnostic for WDM [3]. Specifically, I will present a model-free temperature diagnostic [4] based on the well-known principle of detailed balance, but available for all wave numbers, and a new idea to directly extract the electron— electron static structure factor from an XRTS measurement [5]. As an outlook, I will show how new PIMC capabilities will allow to give us novel insights into electronic correlations in warm dense quantum plasmas, leading to unprecedented agreement between experiments [6] and theory.
[1] M. Bonitz et al., Physics of Plasmas 27, 042710 (2020)
[2] M. Böhme et al., Physical Review Letters 129, 066402 (2022)
[3] S. Glenzer and R. Redmer, Reviews of Modern Physics 81, 1625 (2009)
[4] T. Dornheim et al., Nature Communications 13, 7911 (2022)
[5] T. Dornheim et al., arXiv:2305.15305 (submitted)
[6] T. Döppner et al., Nature 618, 270-275 (2023)
June 15, 2023
Precision measurement of nonlinear QED coupling parameters via photon-photon scattering
Wendell T. Hill, III
Institute for Physical Science & Technology
Department of Physics, University of Maryland
Multi-petawatt laser pulses of short duration have placed us at the threshold of a new era where novel experimental investigations of nonlinear quantum electrodynamics (QED) will be possible. Never before feasible tests of QED from the photon side, and the intimate coupling between QED and the quantum vacuum are on the horizon. The very essence of the vacuum is entangled with a fundamental tenet of quantum physics – quantum fluctuations – virtual particles and antiparticles (e.g., electron-positron pairs) fluctuating into and out of existence. Quantitative measurements of virtual particles not only will challenge calculations from the 1930s, they will also set strenuous laboratory limits for add-ons to the Standard Model of Particle Physics. The Bosonic nature of photons allows arbitrarily large numbers of photons to pile up in one location. Classical electrodynamics would naively suggest than nothing unusual will happen when focusing laser pulses to higher and higher intensity in the vacuum until the so-called Schwinger limit, Icr ≃ 2×1029 W/cm2 is reached, where real matter is coaxed, albeit not so gently, out of negative energy states. Long before Icr, however, QED warns us that the linear response of light propagating in vacuum, as Maxwell equations demand, gives way to a nonlinear behavior – light-light interaction. Post-Maxwellian theories, such as QED and Born-Infeld, allow virtual pairs to mediate this interaction between photons that can be viewed, to some extent, as light propagating through material. Before real pairs emerge, however, QED predicts virtual pairs will cause the vacuum to become birefringent. This effect is expected to become unambiguously discernible in photon-only experiments between 1023 and 1025 W/cm2, arguably just around the corner. In this talk we will discuss one possible way to measure the birefringence via photon-photon scattering, what new physics can be learned in such a measurement, and the technical challenges impeding the realizations of such measurements. In addition, I will present recent advances we have made toward addressing some of these challenges, one of which is shown in the figure.
June 1, 2023
Americans’ Views of Fusion Energy:Implications for Sustainable Public Support
Professor Carol Silva & Professor Hank Jenkins-Smith
Oklahoma University
The successful development of fusion energy will require addressing both technical and social challenges. In this paper we focus on the latter, using survey data from a representative sample of the US public to evaluate prospects for sustainable public support for fusion. We demonstrate that while fusion is broadly viewed in a generally positive light across age, gender and partisan groups, most people acknowledge knowing little about the technology. The current array of images and emotions associated with fusion energy technologies tends to be positive, particularly in comparison with those evoked by traditional fission nuclear energy. Positive views of fusion get a boost from technological optimism, but connection to and fear of fission nuclear energy tends to reduce support. Trust for regulators and operators of prospective fusion energy facilities is currently quite high and is strongly associated with support for fusion energy. Implications are that fusion has the potential to retain broad public support, but developers and regulators need to avoid the kinds of excessive unproven promises and high-profile accidents that have plagued fission. Investments in a regulatory process grounded in trust, robust technological designs, and a culture of responsible safety will be needed to sustain public support for fusion energy.
May 18, 2023
Some Progress in Modeling Warm and Hot Dense Matter
Dr. Charles Starrett
Los Alamos National Laboratory
Experiments that measure the optical properties of warm and hot dense plasmas have pointed to a need to improve our physics models, not only for opacity, but also for equation of state. Here we review a persistent effort carried out at Los Alamos to achieve this goal. We start with the motivating experiments, then summarize the various improvements to our models, and end with a newly developed method that aims to take us a step closer to consistent production of EOS and opacity quantities.
April 20, 2023
The Next Frontier: Engineering Fusion Power
Dr. Susana Reyes
Xcimer Energy Corporation
Over the recent decades, the US DOE Fusion Energy Science program has been strongly focused on sponsoring plasma science research at domestic facilities and international burning plasma research for the international ITER project. Recent scientific achievements, including NIF’s remarkable breakthrough, are fueling new interest from both public and private capital in the development of technologies to harvest the power from burning plasmas. While the domestic Fusion Energy Sciences program has traditionally prioritized Magnetic Fusion Energy (MFE) research, the record breaking NIF results together with significant advances in laser technology have opened new opportunities for attractive plant concepts based on Inertial Fusion energy (IFE). In this talk, we will discuss some of the key technologies that are needed to harness fusion power and to be able to design and build robust and reliable systems that can convert fusion products to useful forms of energy in a reactor environment.
April 13, 2023
Nuclear Physics for and with the National Ignition Facility

Lee Bernstein
Lawrence Berkeley National Laboratory
The neutron-rich high energy density plasma (HEDP) present in NIF capsule at maximum compression provides a unique laboratory for elemental formation in astrophysical environments due to plasma-induced alterations in the angular momentum of the compound nucleus. In this talk I will review historical data that demonstrates the role of compound nuclear states and present the idea for an experiment that could be carried out at the NIF. I will also present facilities and capabilities at UC-Berkeley and LBNL that can be used to aid in the development of new NIF nuclear diagnostics.
March 23, 2023
National Academies report: Fundamental Research in High Energy Density Science
Dr. Félicie Albert
Deputy Director, HEDS Center and Jupiter Laser Facility
Lawrence Livermore National Laboratory
High energy density (HED) science has critical applications for society from fusion energy to sustaining the US nuclear deterrent, while also contributing to broader scientific questions such as understanding planets and their origins. The next decade of HED science will be instrumental to growing our understanding and in the development of new technologies and processes. A new National Academies’ report, Fundamental Research in High Energy Density Science, identifies key challenges and science questions for the field for the coming decade and proposes ways to address them.
March 16, 2023
Edison Liang
Rice University
This talk will present recent results from a series of experiments using the ~130 J, ~ 140 fs Texas Petawatt laser in Austin, Texas to irradiate high-Z (Au, Pt, Re etc.) targets of mm - cm thickness, at laser intensities up to ~5x1021W/cm2. We report the creation of super-high-flux gamma-rays with energy >8 MeV and photo-neutrons via the (g,n) reaction near giant dipole resonance energies (8 - 20 MeV), We detected up to ~ several x 1012 gamma-rays > 8 MeV (~3% of incident laser energy) and ~ 1010 photo-neutrons per shot. Due to the short pulse and narrow gamma-ray cone (~17o half-width) around laser forward, the peak emergent gamma-ray flux >8 MeV reached ~1027 gammas/cm2/sec, and the peak emergent neutron flux reached ~1020 neutrons/cm2/sec. Such intense gamma-ray and neutron fluxes will facilitate the study of physical processes requiring super-high-flux of neutrons or gamma-rays, such as the creation of r-process elements and dense e+e- pair creation. These results may also have implications for the transmutation of nuclear waste.
March 9, 2023
Fluid instabilities and interfacial mixing in high energy density plasmas
Snezhana I. Abarzhi
The University of Western Australia
Rayleigh-Taylor (RT) and Richtmyer-Meshkov (RM) instabilities and RT/RM interfacial mixing govern a broad range of processes in high energy density plasmas, in nature and technology. Examples include the RT/RM instabilities quenching ignition in inertial confinement fusion, the blast wave induced RT/RM mixing in supernova remnants, and RT/RM dynamics influencing materials’ transformation in nano-fabrication. In high energy density settings, at astrophysical and at atomic scales, RT/RM flows are driven by variable accelerations and strong shocks, have sharply and rapidly changing fields, and are anisotropic, non-uniform, and statistically unsteady. Their dynamics depart from canonical scenarios; yet, they can exhibit self-organization and order. We employ the group theory approach to analyze RT/RM dynamics with variable accelerations typical in high energy density plasmas. We directly link the conservation laws governing RT/RM dynamics to the symmetry-based momentum model, precisely derive the model parameters and yield rigorous analytical solutions in the scale-dependent and scale-invariant regimes. We discover the special self-similar class in RT/RM mixing with variable acceleration, and explore its symmetries, scaling laws, spectral shapes, correlations and fluctuations. We reveal that the self-similar dynamics can vary from super-ballistics to sub-diffusion depending on the acceleration and retain memory of the initial conditions for any acceleration. The obtained results are consistent with the existing experiments and numerical simulations, and explain the long-standing puzzles observed in RT/RM experiments at high Reynolds numbers. We propose the experiments at the National Ignition Facility to implement the theory frontiers. We discuss perspectives, unexplored before, for better understanding, and ultimately – controlling, fluid instabilities and interfacial mixing in high energy density plasmas, from supernovae to fusion.
March 7, 2023
Plasma instabilities: Interface dynamics and flow fields structure
Snezhana I. Abarzhi
The University of Western Australia
Interface and mixing and their non-equilibrium kinetics and dynamics couple micro to macro scales, and are ubiquitous to occur in fluids, plasmas, and materials, in high energy density regimes. Stellar evolution, plasma fusion, reactive fluids, purification of water, and nano-fabrication are a few examples of many processes to which dynamics of interfaces is directly relevant. This talk presents the rigorous theory of the stability of the interface – a phase boundary broadly defined. We directly link the structure of macroscopic flow fields to microscopic interfacial transport, quantify the contributions of macro and micro stabilization mechanisms to interface stability, and discover the fluid instabilities never previously discussed. In ideal and realistic fluids, the interface stability is set primarily by the interplay of the macroscopic inertial mechanism balancing the destabilizing acceleration, whereas microscopic thermodynamics create vortical fields in the bulk. By linking micro to macro scales, the interface is the place where balances are achieved.
March 2, 2023
From Thin Air: Diffractive Plasma Optics for Next Generation Light Sources
Matthew Edwards
Stanford University
The light intensity that can be produced by large lasers is limited by optical damage. Replacing standard optical components with plasma, which tolerates far higher intensity, provides a route to compact ultra-high-power lasers. Here, we will discuss how diffractive plasma optics enable the design of compact and powerful lasers by minimizing plasma instabilities while taking advantage of the high damage threshold of plasma. We will show recent experimental results on improving and characterizing the diffraction of intense femtosecond pulses from ionization gratings, including direct measurements of the wavelength-scale modulations of plasma density that make up these structures. This talk will also cover the designs for short pulse laser systems and plasma lenses that use diffractive plasma. Taken together, these experimental and computational results suggest adding ionization optics to the toolkit of components available to high-power laser systems.
February 16, 2023
Laboratory opacity measurements for stellar interiors
James E. Bailey
Sandia National Laboratories, Albuquerque, New Mexico
Nearly a century ago, Eddington [1] recognized that the attenuation of radiation by stellar matter controls the internal temperature profiles within stars like the Sun. Opacities for high energy density (HED) matter are challenging to calculate because accurate and complete descriptions of the energy level structure, equation of state, and plasma effects such as continuum lowering and line broadening are needed for partially ionized atoms. This requires approximations, in part because hundreds of millions, or billions in some cases, of bound-bound and bound-free electronic transitions contribute to the opacity. Opacity calculations, however, have never been benchmarked against laboratory measurements at stellar interior conditions. Laboratory opacity measurements were limited in the past by the challenges of creating and diagnosing sufficiently large and uniform samples at stellar interior conditions. In research conducted over more than 15 years, we developed an experimental platform on the Z facility and measured [2,3] wavelength-resolved opacity at electron temperatures Te = 155-200 eV and densities ne = 0.7 – 5.0 x 1022 cm-3 - conditions very similar to the radiation/convection boundary zone within the Sun. Models agree with data at the lower temperature and densities, but notable model-data discrepancies arise at higher temperatures and densities. The comparisons raise questions about how well we understand the behavior of atoms embedded in high energy density plasma. These measurements may also help resolve decade-old discrepancies between solar model predictions and helioseismic observations. This talk will provide an overview of the measurements, investigations of possible errors, and ongoing experiments aimed at testing hypotheses to resolve the model-data discrepancy.
[1] A.S. Eddington, The Internal Constitution of the Stars (Cambridge Univ. Press, Cambridge, 1926).
[2] J.E. Bailey et al., Nature 517, 56 (2015).
[3] T. Nagayama et al., Physical Review Letters 122, 235001 (2019).
February 9, 2023

Elizabeth Grace
HEDS Postdoctoral Fellow
Short pulse (<10ps), high-intensity (>10^18 W/cm^2) laser systems can be used to generate and probe extremely high energy and density conditions of matter. The plasmas produced by these high intensity laser systems can act as compact radiation sources, can emulate astrophysical phenomena like supernova and centers of giant planets, and even allow access to fusion regimes. Besides fundamental plasma physics, these ultra-intense laser-matter interactions also lend themselves to impactful scientific applications, including homeland security, renewable energy, and state-of-the-art medical techniques. A continuing fundamental need in the field of laser-driven High Energy Density (HED) and plasma physics is the accurate and precise spatial and temporal characterization of the laser pulse, which would provide valuable insight into the foundational physics that drive these interactions. Laser-plasma interactions are complex, rapidly evolving, and highly sensitive to shot-to-shot variations in laser parameters, such as laser peak intensity, pulse duration, pre-pulse, and focal spot, and/or thermal instabilities. Even under nominally identical laser conditions, small variations can drastically influence outcomes. However, in typical HED experiments currently, the complexity of the 3-D laser electric field can mean that the wavefront is not often characterized, or that it is characterized in a surrogate setup or surrogate shot. To accurately understand these interactions, on-shot experimental techniques must be established and implemented. I will discuss the development of a single-frame laser characterization diagnostic for novel use on high-intensity, low repetition rate laser systems, its adaptation to high-repetition rate (>Hz) laser systems, its use in diagnosing and optimizing an ultra-intense laser system, and its role in developing a more complete understanding of the underlying laser-plasma interaction physics. Breakthroughs in these measurement capabilities can unlock an entirely new regime of experimental measurement, deliver a novel capacity to determine and assess pivotal factors that limit more precise control of laser-driven radiation sources, and serve as a necessary tool to improve laser-plasma interaction predictive capability.
January 26, 2023
Building a Virtual Framework to Model In-Situ Laser Shock Experiment
Professor Avinash Dongare
Materials Science and Engineering, University of Connecticut
Short-pulsed lasers have enabled the capability to investigate the dynamic response of metals at extreme strain rates of loading. The shock wave interactions with the rear surface allow the study of several dynamic phenomena in materials, such as shock compression behavior, spall failure, generation of ejecta, and the acceleration/impact of micro-flyers or particles. However, the current efforts to understand the plasticity mechanisms are primarily limited to the characterization of recovered microstructures. Recent advances allow the characterization of these mechanisms in real-time using in situ diffraction experiments (XRD). However, the ability to quantify the contributions from these mechanisms is lacking using experiments alone. As a result, current trends focus on developing computational tools to predict microstructure evolution during the various stages of laser-material interactions at the experimental length and time scales. This talk will present the current efforts at building a virtual framework to complement the interpretation of the results obtained using in situ laser shock experiments. At the atomic scales, we use classical molecular dynamics (MD) simulations to successfully capture various deformation modes (dislocation slip, deformation twinning, and phase transformation) in FCC and BCC metals. The use of simulated diffractograms at various stages of evolution using virtual XRD simulations enables the ability to understand the plasticity contributions to peak shifts/splitting/broadening behavior. A new virtual texture analysis (VirTex) algorithm is developed to characterize deformed microstructures, enabling the creation of simulated EBSD maps to compare with experimental EBSD maps. VirTex characterization enables the investigation of the role of grain orientations and misorientations on the phase/twinning variant selections during shock compression/release and the void nucleation behavior during spall failure. Modeling the laser-metal interaction uses a hybrid atomistic-continuum method that combines classical MD simulations with a two-temperature model (TTM) to accurately describe the ablation and spallation, melting, shock compression, and spall failure behavior. These capabilities of the MD and MD/TTM simulations are now extended to the scales of laser shock experiments using the quasi-coarse-grained dynamics (QCGD) simulations. This talk will demonstrate the ability of QCGD and QCGD/TTM simulations to model the phase transformation behavior of Fe systems, void collapse in Ta systems, and the acceleration of laser-driven flyers at the length and time scales of laser shock experiments
January 19, 2023
Is There a Better Route to Fusion?

Dr. Todd H. Rider
Rider Institute / Massachusetts Institute of Technology (MIT)
Nuclear reactions, which rearrange protons and neutrons within the nucleus, can release up to ~106 more energy than chemical reactions, which rearrange the surrounding electrons. For over 90 years, scientists and engineers have tried to develop attractive ways to extract that nuclear energy. Fission reactors work but are relatively expensive and produce large amounts of radioactivity. Thus far, candidate fusion reactors have appeared even more expensive yet still fairly radioactive, and struggle to produce more electrical energy output than the electrical energy input they consume. This presentation will “rederive” fusion (and other possible nuclear) energy systems from first principles, checking at each step along the way whether there might be better approaches that have not yet been fully explored.
January 12, 2023
Building a Wet Planet from Dry Material
S.-H. Dan Shim
School of Earth and Space Exploration, Arizona State University
It has been believed that water-rich planets are formed outside the snow line. However, discovery of many close-in transiting sub-Neptunes, if at least some of them are water worlds, challenges the notion. Therefore, sub-Neptunes have been believed to be instead large Earth-like planets with thick hydrogen rich atmosphere. We have conducted a series of experiments under the pressure-temperature conditions expected at the boundary between hydrogen-rich atmosphere and rocky interior of a sub-Neptune. We found reaction between hydrogen and magma which can unlock oxygen from silicate magma and enable oxygen to react with hydrogen to form water. The chemical reaction can convert a dry hydrogen-rich planet to a water-rich planet inside the snow line. I will also discuss how such reaction can impact the atmosphere and the habitability of super-Earth exoplanets, many of which may be converted from sub-Neptunes.
June 20, 2023
Japan Speaker:
“Magnetic field dominated proton beam dynamics in focusing plasma devices”
Alessio Morace
Institute of Laser Engineering, Osaka University
High Energy Density Physics is the field of physics dedicated to the study of matter and plasmas in extreme conditions of temperature, densities, and pressures. It encompasses multiple disciplines such as material science, planetary science, laboratory, and astrophysical plasma science. For the latter, High Energy Density states can be accompanied by extreme radiation environments and super-strong magnetic fields. The creation of high energy density states in the laboratory consists in concentrating/depositing large amounts of energy in a reduced mass, typically solid material sample or dense plasma, over a time shorter than the typical timescales of heat conduction and hydrodynamic expansion. Laser-generated, high current-density ion beams constitute an important tool for the creation of High Energy Density states in the laboratory. Focusing plasma devices, such as cone-targets are necessary in order to focus and direct these intense beams towards the heating sample or dense plasma, while protecting the proton generation foil from the harsh environments typical of an integrated high-power laser experiment. A full understanding of the ion beam dynamics in focusing devices is therefore necessary in order to properly design and interpret the numerous experiments in the field. In this work, we report a detailed investigation of large-scale, kilojoule-class laser-generated ion beam dynamics in focusing devices and we demonstrate that high-brilliance ion beams compress magnetic fields to amplitudes exceeding tens of kilo-Tesla, which in turn play a dominant role in the focusing process, resulting either in a worsening or enhancement of focusing capabilities depending on the target geometry.
May 16, 2023
US Speaker:
“Design of the first fusion laboratory experiment to achieve target gain > 1”
Dr. Annie Kritcher
Lawrence Livermore National Laboratory
The inertial fusion community has been working towards ignition for decades, since the idea of inertial confinement fusion (ICF) was first proposed by Nuckolls, et al., in 1972. On August 8, 2021, and Dec 5th, 2022, the Lawson criterion for ignition was met and more fusion energy was created than laser energy incident on the target at the National Ignition Facility (NIF) in Northern California. The first experiment produced a fusion yield of 1.35 MJ from 1.9 MJ of laser energy and appears to have crossed the tipping-point of thermodynamic instability according to several ignition metrics. Building on this result, improvements were made to increase the fusion energy output to >3MJ from 2.05 MJ of laser energy on target, resulting in target gain exceeding unity for the first time in the laboratory. This result is important in that it proves that there is nothing fundamentally limiting controlled fusion energy gain in the laboratory. The presentation will detail the changes made to achieve this result.
April 11, 2023
Japan Speaker:
“Laser-Driven Neutron Generation Realizing Single-Shot Resonance Spectroscopy”
Professor Akifumi Yogo
Institute of Laser Engineering, Osaka University
Neutrons are a powerful tool for investigating the structure and properties of materials. Ultracompact laser-driven neutron sources (LDNS) are attracting interest as the next-generation neutron source after nuclear reactors and accelerator-based facilities. However, understanding the laser-driven ion acceleration mechanism for neutron generation and establishing the scaling law on the neutron yield are essential to improve the feasibility of LDNS. Here, we report on the mechanism that accelerates ions with spectra suitable for the neutron generation and identify how neutron yield changes with laser power. We focus a laser on a foil of deuterated polystyrene. This generates a plasma that sources and accelerates ions, which in turn bombard a block of beryllium that acts as the neutron source. By measuring the ion spectra, we identify distinct rates of expansion of different ion species, which play a key role in the formation of the ion field. We also find that the neutron yield increases with the fourth power of the laser intensity on the target, which offers a guideline for eventually increasing the neutron flux. Finally, we demonstrate single-shot analysis of composite materials by neutron resonance transmission analysis. With an energy resolution of 2.3% nearly 2 m from the LDNS, this leads to the analysis of elements and isotopes in less than a microsecond, allowing for high-speed nondestructive inspection.
March 14 ,2023
Japan Speaker:
“Research activities and experimental capabilities on high-energy-density science at X-ray free-electron laser facility, SACLA”
Dr. Toshinori Yabuuchi
Japan Synchrotron Radiation Research Institute
High-energy density (HED) science is one of the major fields of science performed at SACLA, the X-ray free electron laser (XFEL) facility in Japan. Since we started the user operation of SACLA in 2012, physics and material properties under HED states have been studied using high-power optical lasers or ultra-intense XFELs. Both femtosecond and nanosecond high-power optical lasers are implemented at SACLA and can create the matter under HED states. The XFEL then diagnoses the subjects on a single-shot basis because of its brilliance with superior temporal and spatial resolutions. The XFEL also works as a pump to produce the HED states once it is tightly focused down to the spot in the sub-micron scale. The experimental capabilities and recent research activities will be introduced in this talk.
US Speaker:
“Strong Interaction and temperature effects in density functional theor”
Assistant Professor Aurora Pribram-Jones
Department of Chemistry and Biochemistry
University of California, Merced
The strictly correlated electron approach to density functional theory, first proposed by Seidl and coworkers [1-4], offers a useful perspective on thermal density functional theory and one of its application areas, simulations in the warm dense matter regime. In this region of phase space, many of the assumptions of traditional Kohn-Sham density functional theory no longer hold, requiring exchange-correlation free energy approximations that include explicit temperature dependence and better handling of complicated ionization processes. Formal analysis of the strong interaction limit for thermal ensembles and the competition between strong interaction and temperature in complicated physical systems will be discussed.
[1] M. Seidl, Phys. Rev. A 60, 4387 (1999).
[2] M. Seidl, J. P. Perdew, and M. Levy, Phys. Rev. A 59, 51 (1999).
[3] M. Seidl, P. Gori-Giorgi, and A. Savin, Phys. Rev. A 75, 042511 (2007).
[4] P. Gori-Giorgi, G. Vignale, and M. Seidl, J. Chem. Theory Comput. 5, 743 (2009).
February 14, 2023
Japan Speaker:
“Dynamic high-pressure research using intense photon beams”
Associate Professor Norimasa Ozak
Graduate School of Engineering, Osaka University
Institute of Laser Engineering, Osaka University
High energy density states of matter are being investigated using intense photon beams, e.g., high-power optical lasers and X-ray free-electron lasers (XFEL). We developed a research platform for high-energy density science at the SACLA XFEL facility [1,2]. Here, some recent achievements obtained on the platform is presented; 1) X-ray diffraction observations of shock-compressed diamond [3-5], 2) femtosecond and sub-micron resolution radiography of shock-compressed matter [6].
[1] Y. Inubushi, T. Yabuuchi, T. Togashi, et al., Appl. Sci. 10, 2224 (2020).
[2] T. Okuchi, Y. Seto, N. Tomioka, et al., Nat. Commun. 12, 4305 (2021).
[3] K. Katagiri, N. Ozaki, Y. Umeda, et al., Phys. Rev. Lett. 125, 185701 (2020).
[4] K. Katagiri, N. Ozaki, K. Miyanishi et al., Phys. Rev. B 101, 184106 (2020).
[5] K. Katagiri, N. Ozaki, D. Murayama, et al., Phys. Rev. B 105, 54103 (2022).
[6] G. Rigon, B. Albertazzi, T. Pikuz, et al., Nat. Commun. 12, 2679 (2021).
US Speaker:
“Update on Inertial Fusion Energy (IFE) Activities at LLNL”
Tammy Ma
Lawrence Livermore National Laboratory
With the recent breakthrough ignition results on the National Ignition Facility, the White House announcement of a decadal vision to accelerate the commercialization of fusion energy, initial congressional appropriations to restart a US Inertial Fusion Energy (IFE) program, and a rapidly growing private fusion energy sector, the time is now to revitalize the national IFE program as a potential path to energy and climate security. LLNL has kicked off an Institutional Initiative in IFE to develop and implement a strategy to build towards fusion energy for the future. In this talk, we will provide a summary of IFE activities at LLNL.
January 10, 2023
Japan Speaker:
"Ultra-fast neutron diagnostics for nuclear burning history"
Professor Yasunobu Arikawa
Institute of Laser Engineering, Osaka University
National ignition facility had succeeded to achieve fusion ignition. This is the first time to see a burning plasma in lab in human history. The next step we have to pursue is understanding about the burning physics in the fusion plasma. Hydro dynamic simulations or recent measurements at NIF speculate the burn duration, which is overall a period of the burn propagation of NIF implosion, is about 80-100 ps, therefore a detector with a picosecond temporal resolution is required to see the burn process. However, there is no fast neutron detectors with the sufficient temporal resolution. In this talk I introduce a new neutron detector with one picosecond time-scale resolution which will potentially be a next generation key diagnostic in NIF. It utilizes an electro-optical reaction and ultra-short chirped pulse laser probe instead of the conventional scintillation emission or Cherenkov emission. The details will be in the talk.
US Speaker:
“Review of the first charged-particle transport coefficient comparison workshop”
Paul Grabowski
Lawrence Livermore National Laboratory
We present the results of the first Charged-Particle Transport Coefficient Code Comparison Workshop, which was held in Albuquerque, NM October 4–6, 2016 in the context of planning for a second workshop. In the first workshop, scientists from eight institutions and four countries gathered to compare calculations of transport coefficients including thermal and electrical conduction, electron–ion coupling, inter-ion diffusion, ion viscosity, and charged particle stopping powers. We give general background on Coulomb coupling and computational expense, review where some transport coefficients appear in hydrodynamic equations, and present the submitted data. Large variations are found when either the relevant Coulomb coupling parameter is large or computational expense causes difficulties. We will present scientific goals and open questions for the next workshop. Understanding the general accuracy and uncertainty associated with such transport coefficients is important for quantifying errors in hydrodynamic simulations of inertial confinement fusion and high-energy density experiments.
December 15, 2022

Alex Do
Lawrence Livermore National Laboratory
Phase contrast imaging is a commonly used technique in optical and x-ray radiograph to image weakly absorbing phase objects through diffraction across transverse phase gradients. Recently, an X-ray phase contrast imaging platform has been developed on NIF, the Refraction Enhanced Radiography (RER), to study Inertial Confinement Fusion (ICF) indirect drive capsule implosion [1]. RER provide the direct observation of density gradients with higher contrast than classic absorption. RER will provide insight into the observed reduced compression in recent ICF implosions [2]. We focused our efforts on two different phases: We will present a first series of experiments is aiming to study the effect of the N+1 shock, the shock coming from the reflection of the rarefaction wave; and a second one is looking into measuring the early time trajectory of the ice-ablator interface. Following the high-quality data obtained from these experimental campaigns, we present the design of a new platform that is being developed for hydrodynamic instabilities studies, specifically for the reshock experiments [3]. It will allow the observation of shock propagation inside a low-density CRF foam and the adjustment of the laser drive to avoid secondary reflected shock.
[1] E.L. Dewald, O.L. Landen, et al., High En. Dens. Phys. 36, 100795 (2020).
[2] D.S. Clark, S.W. Weber, et al., Phys. Plasmas 26, 050601 (2019).
[3] S. Nagel, et al., Phys. Plasmas. 29, 032308 (2022).
December 1, 2022
Quantum simulations at extreme conditions: warm dense matter and planetary interior

Felipe Gonzalez
Project Scientist, University of California, Berkeley
PhD in Physics, Univ. de Chil
Computer simulations based on quantum mechanics are useful because they are predictive. Approaches based on first-principles have demonstrated that the properties of matter can be predicted very accurately, even at extreme conditions of pressure and temperature present in shock or ramp compression experiments and planetary interiors [1,2]. Using these techniques, we can obtain equations of state (EOS) of different materials and predict different phase transitions that can help guide experiments and to develop new theoretical models for matter at extreme conditions. Here we show how the combination of two different first-principles approaches, density functional theory molecular dynamics (DFT-MD) and path integral Monte Carlo (PIMC), enables us to develop EOS of materials that span a wide range of temperatures and densities, including warm dense matter (WDM) regime, and to obtain shock Hugoniot curves that span across the L-shell and K-shell ionization regimes [3,4]. We study the nonideal mixing effects in WDM [5] and provide a code that generates new EOS of materials [6]. In addition, we show how DFT-MD simulations can be applied to address a number of problems relevant to planetary science, including the erosion of Jupiter's core [7], miscibility of planetary materials [8], and crystallization of super-Earth cores
[1] F. Soubiran et al., J. Chem. Phys 151, 214104 (2019).
[2] F. González-Cataldo et al., PRB 101, 024107 (2020).
[3] F. González-Cataldo and B. Militzer, AIP Conf. Proc 2272, 090001 (2020).
[4] F. González-Cataldo et al., Phys. of Plasmas 27, 092706 (2020).
[5] B. Militzer et al., J. of Chem. Phys. 153, 184101 (2020).
[6] B. Militzer et al., PRE 103, 013203 (2021).
[7] F. González-Cataldo et al., The Astroph. J. 787, 79 (2014).
[8] T. Kovacevic et al., Sci. Rep. 2, 13055 (2022).
November 10, 2022
Opportunities and Challenges in AI-driven High Repetition Rate HED Experiments
Derek Mariscal
Lawrence Livermore National Laboratory
As lasers facilities continue to grow and advance in repetition rate capabilities (>shot per minute), data generation will increase by several orders of magnitude compared to today’s premier ~shot/hour facilities. Replacing human-guided experience and intuition with AI-like systems will be necessary in simulations, driver control, and diagnostic analysis to enable utilization of next-generation laser facilities to their full potential. There are many opportunities to develop these key enabling technologies that each face unique challenges. Advances in computational hardware and machine learning technologies provide a path to operate experiments intelligently at rates of 10-Hz and beyond. This talk will outline the vision for high-repetition-rate laser-driven experimentation and overview several key areas of recent advancement that will ultimately enable acceleration of scientific discovery by several orders of magnitude.
November 8, 2022
Generation and dynamics of seed magnetic fields in collision less plasmas
Professor Nuno F.G. Loureiro
Department of Nuclear Science and Engineering, Department of Physics
Deputy Director, Plasma Science and Fusion Center
Massachusetts Institute of Technology
Magnetic fields abound throughout the universe. Their strengths are such that they are dynamically important; and they tend to be associated with some of the most energetic phenomena that we observe. Astrophysical magnetic fields are generally believed to be created and sustained by the turbulent dynamo process, which relies on seed magnetic fields to act upon and amplify to the observed levels. Traditionally, emphasis has been placed on the Biermann battery mechanism as the originator of such seeds – this is also the case for magnetic fields in ICF-relevant contexts.
In this talk, I will discuss how configurations that trigger the Biermann battery are also unstable to the Weibel instability, provided that the plasma is weakly collisional and that there is enough scale separation between the temperature- and density-gradient scale lengths and the electron scales [Schoeffler et al., PRL 2014; Sutcliffe et al., arXiv:2209.02565]. Furthermore, I will argue that even something as generic as a sheared flow suffices to trigger the Weibel instability [M. Zhou et al., PNAS 2022].
For sufficiently large systems, the amplitude of the Weibel fields far exceeds that of the Biermann fields; however, Weibel fields are at electron scales, whereas Biermann fields are system size. These findings thus suggest a different generation and amplification paradigm: one where Weibel fields are the dominant seed fields, and first undergo several generations of mergers until they reach scale lengths where they can be efficiently amplified by turbulent flows [Zhou et al., JPP 2020].
November 3, 2022
From atoms to planets and stars: what can we learn from ab initio simulations?
François Soubiran
CEA DAM-DIF, 91297 Arpajon Cedex, FRANCE
Research on planets and stars is very vivid with numerous dedicated observational campaigns. For instance, the transit detection method led to exquisite discoveries in the field of exoplanet, triggering some important paradigm shifts in our conception of planetary systems. But these observational data rely on the accurate determination of their stellar companion properties. In order to comprehend the structure, evolution and formation of the different compact objects it is crucial to understand the microphysics at play. With the advent of significantly improved computer capabilities and new numerical techniques, ab initio simulations proved to be an important asset in this area. They provide precise determinations of the physical properties of materials relevant for planets and stars on a wide range of thermodynamic conditions and effectively complement the experimental results. In this presentation I will give a few examples of the capabilities of such simulations at the atomic scale. I will also explain how the microphysics can provide strong constraints on the global properties of stars and of planets, and on the habitability of exoplanets.
October 27, 2022
New Perspectives for Warm Dense Matter Theory: from Quantum Monte Carlo to Temperature Diagnostic

Professor Tobias Dornheim
Center for Advanced Systems Understanding (CASUS), D-02826 Görlitz, Germany
Helmholtz-Zentrum Dresden-Rossendorf (HZDR), D-01328 Dresden, Germany
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 cutting-edge technological applications such as inertial confinement fusion and the discovery of novel materials. In the laboratory, WDM is studied experimentally in large facilities around the globe, and new techniques have facilitated unprecedented insights into exciting phenomena like the formation of nanodiamonds at planetary interior conditions [1]. Yet, the interpretation of these experiments requires a reliable diagnostics based on accurate theoretical modeling, which is a notoriously difficult task [2]. In this talk, I give an overview of recent developments in this field [3,4], which will allow for the first time to rigorously treat the intricate interplay of Coulomb coupling with thermal excitations and quantum degeneracy effects. Moreover, I show how quantum Monte Carlo simulation techniques will help to decisively improve density functional theory (DFT) simulations of WDM, thereby opening up new perspectives, such as the experimental and theoretical study of nonlinear effects [5,6]. Finally, I will present a new idea to extract the exact temperature from an X-ray Thomson scattering experiment without any models or simulations [7].
October 25, 2022
Improving our models of nonlocal transport
Professor Christopher Ridgers
University of York, UK
Inertial confinement fusion involves the creation of plasmas far from local thermodynamic equilibrium. The temperature scale-length in the plasma can become shorter than the collisional mean free path of the heat-carrying electrons and thus the thermal transport can therefore become nonlocal. How to capture this in our modelling tools is a long-standing problem in the field. Nonlocal transport was identified as one cause of discrepancies between LASNEX modelling and the National Ignition Campaign. The most common way to capture nonlocal transport is to continue using a diffusive, LTE model, but to limit the heat flux to prevent it becoming unphysical. This flux limiter can only be tuned post-hoc to match experiments and therefore its use limits the predictive capability of codes. Non-LTE thermal transport models should do a better job of capturing nonlocal transport but also necessarily make several assumptions. Here we present recent work to assess the accuracy of various models for nonlocal transport, using both ab-initio calculations and simplified experiments. We find that nonlocal modes can be accurate to within ~10% over a relatively wide range of parameters in the absence of magnetic fields. Self-generated magnetic fields substantially complicate this picture though and we will present a simplified experimental platform for investigating the effects of magnetic field, for example directly measuring the advection of magnetic field by the heat flow (the Nernst effect) in a plasma for the first time.
October 13, 2022
Professor Erin R. Johnson
Department of Chemistry
Dalhousie University, Canada
The development of dispersion corrections has allowed the application of density-functional theory (DFT) to a wide range of problems in materials science. One such problem is molecular crystal structure prediction (CSP) of a given compound from its molecular diagram. CSP requires accurate and efficient evaluation of energy differences between candidate structures to determine the most thermodynamical stable form(s), which should be seen experimentally. Identification of likely crystal structures further allows prediction of emergent properties, such as charge transport and photoluminescence. Another example where the advent of dispersion corrections was an essential advance is the study of layered materials, such as graphene and transition-metal dichalcogenides (TMDCs). The 2D electrides are a particularly novel class of layered materials, in which the positively charged atomic layers are separated by interstitial regions of confined electrons. In this talk, I will highlight recent applications of DFT to molecular crystal structure prediction, with a focus on helicene compounds, which have potential utility as organic electronics. I will also present a study of electride materials and their insertion at metal-TMDC interfaces to improve charge transport. Finally, I will discuss the implementation of our exchange-hole dipole moment (XDM) dispersion model into the FHI-aims code to enable computational modeling of much larger systems than was previously feasible.
October 6, 2022
The High Energy Density Science Center: 2022 year in review

Dr. Frank Graziani
Lawrence Livermore National Laboratory
HEDS Center Director
The High Energy Density Science Center (HEDSC) was established in late 2015 through a joint agreement between the Physical and Life Sciences, Weapons and Complex Integration, and NIF and Photon Science directorates. The Center’s goal is to build a high energy density community through support of, and collaboration with, academic partners and to integrate those efforts with the programs at LLNL. The Center is built around four focus areas: (1) education, (2) outreach through workshops and seminars, (3) workforce pipeline to the programs, and (4) enabling research collaborations between LLNL and academic partners. In this talk, we will present the year FY22 in review and look at what lies ahead in FY23. FY22 saw a collaboration with the WCI Designer Training Program as we offered a survey class in HEDS to staff and students. The Center was also involved in running the Scientific Applications of Quantum Computing Summer school. Another new HEDS Center Fellow was selected, and we will begin the process for selecting our 2023 HEDS Fellow. Besides educating the next generation of HED scientists, the HEDS Center continues training students through internships and thesis opportunities. Our outreach and collaboration activities continue through a vibrant seminar series, university partnerships, a sabbatical program. We welcomed Professor Farhat Beg from UCSD and Franck Delmotte from the University of Paris for sabbatical visits. With the return to on-site work, our seminar series went into a new hybrid mode, thereby serving both the LLNL community and our external partners. Inclusion and diversity are an important aspect of our mission and the Consortium for HEDS (FAMU, UC Merced, Morehouse and LLNL) helps a number of students within CfHEDS. The Consortium’s goal is to provide research and education opportunities in HEDS for under-represented groups and thereby increase diversity in the field. A call for a new HEDS Fellow postdoc position is out and working with UCSD, a course in atomic spectroscopy is planned for the spring quarter of 2023. In FY23 we will continue to foster international collaborations in HEDS, re-engaging with Israel and Japan. We will plan to utilize the recently dedicated University of California Livermore Collaboration Center along with the Livermore Valley Open Campus for workshops and distance learning. Finally, the process for strategic planning will begin in 2023.
September 15, 2022
Modern Data Science & Extreme Physics: Making more of our data on the Z Machine & Beyond

Patrick Knapp
Sandia National Laboratory
The Z machine is the world’s largest pulsed power accelerator where we conduct experiments to study matter in the most extreme states accessible on earth. Results from these experiments are used to advance our understanding of physics in nuclear explosions, nuclear survivability, astrophysics, and planetary cores. These experiments are expensive and rare, necessitating that we utilize all experimental data to the fullest extent possible. In this talk, we will detail our vision for developing and applying the modern data analytics tools that enable efficient and effective use of our data to constrain models and to advance high energy density science and the pursuit of high fusion yield in the laboratory. Statistical inference lies at the heart of many critical tasks, such as feature extraction, hypothesis testing, and parameter estimation. We detail the use of Bayesian methods to constrain experimental quantities of interest by combining disparate sources of data, using examples from fusion experiments on Z. We also discuss the development and application of machine-learned surrogate models that enable expensive analysis methods like Bayesian inference. Combining high fidelity, efficient surrogate models with Bayesian inference opens new opportunities to optimize our experiments and instruments to maximize information gain, providing a quantitative means to guide investments and make decisions in a resource constrained environment. These tools can revolutionize the practice and use science of two impact key decisions.
August 18, 2022
Opacity Measurements on the National Ignition Facility: Preliminary Results

Bob Heeter
Lawrence Livermore National Laboratory
Opacity in a plasma is the material property characterizing X-ray absorption, a key coupling parameter between the “rad” and the “hydro” in radiation-hydrodynamic models. Opacity experiments on Z show significant disagreements with theory at temperatures > 160 eV and electron densities > 2x10^22/cm^3 [J.E. Bailey et al, Nature, 2015]. A higher opacity at these conditions would help resolve longstanding issues with the solar convective zone boundary and the ages of white dwarf stars. However, it has proven very difficult to reconcile theory with the Z data. This motivated development of comparable opacity experiments on the National Ignition Facility (NIF). The Opacity-on-NIF Campaign has begun producing data for X-ray energies 1000-2000 eV at temperatures 130-160 eV and electron densities 0.5 to >3x10^22/cm^3. Measurements at higher temperatures are currently precluded by the onset of high backgrounds. Preliminary transmission measurements for iron and oxygen, at conditions overlapping some of the Z measurements, show trends qualitatively similar to the Z data, but are not final. Quantification and correction of a potential systematic error sources is underway, and peer review in this area is invaluable to improving the accuracy. Ongoing work includes development of a time-gated spectrometer, together with target improvements, to reduce backgrounds, improve spectral resolution, and enable measurements at higher temperatures.
August 11, 2022
Molecular Born-Oppenheimer quantum mechanics as a double gauge theory

Robert Littlejohn
University of California, Berkeley
The physics of polyatomic molecules involves two distinct gauge theories. One is associated with the rotational invariance of the molecule, which endows the nuclear configuration space with the geometrical structure of an SO(3) fiber bundle. This geometry provides the structure within which such issues as the conservation of angular momentum, the construction of nuclear kinetic energy operators, the phase and frame conventions for electronic eigenstates, the construction of diabatic bases, and the geometry of molecular point symmetries are framed. We call this the Coriolis gauge structure; it is associated with a vector potential and a curvature form that play an important role in the physics of the molecule. The second gauge theory is associated with the phase and frame conventions of the electronic eigenstates, which are associated with the Mead-Truhlar-Berry or MTB connection or vector potential and curvature. This gauge structure has its own fiber bundle, which consists of frames of electronic basis states. The MTB vector potential appears in the nuclear kinetic energy as derivative couplings. This talk will discuss the interplay between these two gauge theories and the role that they play in fundamental aspects of molecular physics.
August 4, 2022
The Diversity of Low-mass Exoplanets

Daniel Jontof - Hutter
University of the Pacific
Low mass planets have an extraordinary range in bulk compositions, from primarily rocky worlds to those with deep gaseous atmospheres. As techniques to measure precise masses advance the field of exoplanets towards the regime of rocky worlds, from ultra-short orbital periods to Venus-like distances, we identify bounds on planet compositions from size and incident flux.
We also highlight the complementary datasets of radial velocity spectroscopy and transit timing variations and how their different detection biases affect our interpretation of the planetary mass-radius diagram. We summarize the existing challenges of both techniques and where progress reveals an emerging picture that explains some aspects of the compositional diversity of low-mass planets.
In some cases, planetary mass and radius measurements are approaching precisions where theoretical uncertainties in planet models are the limiting factor in characterizing the bulk composition. Precise masses of exoplanets discovered by the TESS mission, and advances in the equation of state in the high pressure regime, are enabling more precise exoplanet characterizations than ever before in the rocky regime.
July 21, 2022

Kalpani Werellapatha
Lawrence Livermore National Laboratory
We present details of an experimental platform that collects time-resolved x-ray diffraction (XRDt) data from laser-driven dynamically compressed materials at the National Ignition Facility. XRDt probes the atomic structure of phase transformations at extreme thermodynamic conditions in-situ. To record these phase transitions, we use high speed (~1 ns) gated hybridized CMOS sensors, which collect multiple frames of data over a timescale of a few to tens of ns. We record both time-resolved (hCMOS) and time-integrated (image plate) XRD data and register the direct x-ray beam information. The drive-laser intensity is gradually increased to ramp compress thin samples, sandwiched between tamper layers. A pinhole limits the sample size to 400 µm. High-precision velocimetry measurements monitor the pressure history of the sample. A temporally uniform, quasi monochromatic x-ray source of ~10 ns duration is produced by irradiating a ~250 µm thick Ge foil with < ~50 kJ of laser energy at an intended intensity of 2x1015 W/cm2 . The x-ray source time evolution is monitored with a NIF X-ray spectrometer. We use dedicated filters to mitigate x-ray florescence and hard x-rays from hot electrons. The platform has been used to collect XRD from ambient Sn and Pb at 1 Mbar. We discuss challenges with background mitigation strategies and accuracy/resolution of diffraction data. Prepared by LLNL under Contract DE-AC52-07NA27344. LLNL-ABS-828064.
July 7, 2022
Frozen in time: crystallization, fractionation and distillation in white dwarf star

Simon Blouin
University of Victoria, BC Canada
Stars can freeze. When a white dwarf—a dense stellar ember that simply cools down for the rest of time—becomes cool enough, the ions in the degenerate plasma that makes up its core crystallize. During this phase transition, the coexisting liquid and solid ionic mixtures do not have the same composition. This chemical fractionation can release enough gravitational energy to slow down the cooling of the white dwarf for a few billion years. Recent astronomical observations have now identified the signature of this cooling delay and it is much larger than expected, reaching up to 8 billion years. I will discuss how the fractionation and “distillation” of trace amounts of neutron-rich species can solve this observational puzzle.
June 23, 2022
X-ray diffraction measurements at terapascal pressures on the NIF

Amy Jenei
Lawrence Livermore National Laboratory
The crystal structure of a material is an important fundamental basis for understanding its equation of state and properties. The structure at terapascal pressures has an impact on our understanding of exoplanet interiors, and measurements at these conditions are important more broadly, for testing the accuracy of our theoretical tools for predicting material properties at the conditions of relevance for HED and ICF research. We have developed the TARDIS x-ray diffraction diagnostic at the NIF laser facility for measuring structure at these extremes. I will summarize the current status of the diagnostic and present results on two very different materials – carbon and magnesium – collected under the NIF Discovery Science Program. In the case of carbon, we have compressed it in the diamond phase to 2 TPa using ramp-shaped laser pulses and observed it to retain its ambient crystal structure far beyond the predicted regime of stability. The results reveal an inconsistency in our understanding of diamond and suggest some interesting outstanding questions to investigate. In the case of Mg we observed three phase transformations as it is ramp-compressed to 1.3 TPa, broadly consistent with theoretical predictions but also revealing some unexpected new properties.
June 9, 2022
Carbon at Extreme Conditions: Discovery Science with Machine-Learning and Big Computer
Ivan Oleynik
University of South Florida
Carbon at extreme pressures and temperatures is a topic of great scientific interest for several disciplines including planetary science and inertial confinement fusion research. Questions which has long perplexed both experimental and theoretical communities are the existence and potential synthesis of high-pressure post-diamond carbon phases and inelastic response of diamond to strong shock compression. In particular, very recent X-ray diffraction experiments at National Ignition Facility challenged the theoretical prediction of existence of a high pressure BC8 post diamond phase by compressing diamond to gigantic pressures up to 20 Mbar (Lazicki et al, Nature (2021)). By developing machine learning description of interatomic interactions and efficiently applying in quantum-accurate, billion atom molecular dynamics (MD) simulations on pre-exascale 200-petaflop Summit supercomputer, we were able to “computationally synthesize” the long sought BC8 post-diamond phase and uncover a novel mechanism of inelastic deformations in shock compressed diamond. Extreme-scale quantum-accurate MD simulations at experimental time and length scales demonstrate transformative science impact of machine learning interatomic potentials and advanced simulation and computing to predict novel physical phenomena and guide experiments towards observing them.
May 26, 2022
Cognitive Simulations and Virtual Diagnostics to Drive High Repetition Rate Laser Facilities

Timo Bremer
Lawrence Livermore National Laboratory
As high-intensity short-pulse lasers that can operate at high-repetition-rate (HRR) (>10 Hz) come online around the world, the high-energy-density (HED) science they enable will experience a radical paradigm shift. The >1000 increase in shot rate over today’s shot-per-hour drivers translates into dramatically faster data acquisition and more experiments, and thus the potential to significantly accelerate the advancement of HED science. However, fully realizing the potential benefits of HRR facilities requires a fundamental change in the design and execution of experiments done on them. This talk will introduce a cognitive simulation-based framework to couple traditional scientific computing with advanced data analytics, such as deep learning design to ultimately drive a high repetition laser facility with little or no human involvement. In particular the goal is to combine high-fidelity simulations with streaming experimental data to create an automatic system that, driven by the high-level scientific objective of optimizing a short-pulse laser-accelerated proton beam, continuously adapts and optimizes the experiment to provide maximal insights. Furthermore, we will develop a new generation of multi-fidelity, multi-modal surrogate models that encapsulate the knowledge of the best available pre-shot simulations and are capable of predicting, not only the traditional integrated scalar characteristics (e.g., a proton beam energy and flux), but also a full suite of synthetic diagnostics, as well as information on the internal plasma state only accessible through simulations. After describing the long term vision the talk will present recent advances in areas such as representation learning, surrogate modeling, and virtual diagnostics as discuss how these are being integrate into the ALEPH laser system at Colorado State University
May 19, 2022
Exploring relativistic laser plasmas with hard X-ray FELs: Status of HIBEF at European XFEL
Thomas E Cowan
Helmholtz-Zentrum Dresden-Rossendorf and Technische Universität Dresden
The Helmholtz International Beamline for Extreme Fields (HIBEF), at the HED Instrument of the European XFEL, provides high intensity and high power laser drivers, high-pressure diamond anvil cells, and pulsed magnetic fields, for driving samples to extreme conditions. These are provided by an international User Consortium composed presently of HZDR, DESY, STFC-CLF, CNRS (LULI, IMPMC, and CELIA) and LANL. A formal HiBEF inauguration ceremony in August 2021 celebrated the completion of the ReLaX (“Relativistic Laser at XFEL”) system provided by HZDR, and the first year of operation of the DAC Platform provided by DESY. The CLF-provided DiPOLE D100-X system is being commissioned and will be opened for users in 2023, along with the pulsed high field magnets from HZDR.
One of the main motivations for the ReLaX laser of HiBEF was to improve our understanding of relativistic laser-solid interactions, of relevance for applications in laser-ion acceleration, ultrafast radiation sources, and isochoric heating. The present status of HiBEF, and recent progress in developing new XFEL-based techniques for studying relativistic laser-solid interactions, will be described.
May 5, 2022
The Long and the Short of it: How advances in short pulse laser technology influence our understanding of laser plasma interactions in HED Physics
Scott Wilks
Lawrence Livermore National Laboratory
The development of Petawatt-class short pulse laser technology has made it possible to create some of the brightest sources of particles and photons on the planet, albeit at low average power. These high peak power lasers enable sub-nanosecond photon, proton, and neutron radiographic snapshots of dense solids and plasmas, as well as their associated electric and magnetic fields, with near-micron spatial resolution, with the additional ability to create high energy density plasmas via isochoric heating. In this seminar, we show how two specific laser developments are influencing how we think about relativistic laser plasma interactions. First, we discuss how the development of kilojoule class “long” short pulses (from 1 to 20 ps in duration) with large spots (~ 50 micron) made us rethink some of the fundamental electron acceleration mechanisms that underlie short pulse laser matter interactions, and how this is helping us improve these radiographic sources for HED experiments. Next, we will see how the development of new “short” ( from 100 fs to 1 ps) pulse lasers with high average powers as high as 300 kW are forcing us to examine the impact of laser wavelength on our current radiographic sources, while at the same time opening the door to completely new applications that are currently exclusively handled by high average power particle accelerators. These new applications include novel methods for measuring nuclear cross sections, nuclear waste transmutation, and short pulse-based ignition methods for Inertial Confinement Fusion.
April 21, 2022
Advancing HED Opacity Science on Z using Time-Resolved Spectroscopy
Guillaume Loisel
Sandia National Laboratories
Models for the Sun and stars remain uncertain today because opacity models are unable to reproduce previous iron opacity measurements at stellar interior conditions [Bailey et al. Nature (2015), Nagayama et al. PRL (2019)]. Time-resolved spectroscopy using a novel hCMOS Ultra-fast X-ray Imager (UXI) is transforming stellar interior opacity measurements at the Sandia Z facility in three important ways. 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-nanosecond backlighter and one hypothesis for the opacity model data discrepancy is that temporal integration influenced the results. A definitive evaluation for this hypothesis requires direct experimental measurement. 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, measurements of the iron sample temperature and density evolution inevitably lead to refined understanding for the experiment. Improved understanding enables improved experiment design. In fact, time-resolved measurements have already 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 also measured time-resolved Fe absorption spectra for the first time, a first step toward time-resolved opacity. We will discuss the remaining challenges and our strategy to obtain the first time-resolved opacity measurements on Z.
March 31, 2022
3D electron temperature measurements of Inertial Confinement Fusion Hotspot using x-ray emission tomography

Karry Wong
Lawrence Livermore National Laboratory
HEDS Center Post Doc Fellow
3D electron temperature measurements of inertial confinement fusion (ICF) hotspots can help us understand fusion plasmas. They enable us to study hotspot degradation, its energy balance mechanisms, and various of its thermophysical quantities such as pressure and density. In this seminar, I will present a generalization of the use of a class of computed tomography algorithms, Algebraic Reconstruction Techniques (ART), to reconstruct the 3D x-ray emission distributions emitted by the ICF hotspot. This is done in various x-ray energy channels from a very limited number of 2D hard x-ray (18 - 30 keV) penumbral image projections. This diagnostic technique enables the inference of spatially resolved hotspot electron temperatures on the NIF. I will present synthetic data studies that quantify effects of e.g. statistical noise, source geometry, number of lines-of-sight, as well as some experimental data results that exhibit different hotspot geometries.
March 10, 2022
Dynamic Compression of Minerals: Implications for Exoplanetary Interior

Thomas S. Duffy
Princeton University
Department of Geosciences and Institute of Materials
Dynamic compression studies of minerals have important applications to understanding planetary formation, shock metamorphism, and high-pressure phases of deep planetary interiors. Historically, measurements under in situ shock-loading conditions have been restricted to acquiring mostly continuum-level information and the lattice structure could not be determined. With the recent development of user facilities combining laser techniques for shock and ramp compression with x-ray diffraction capabilities, it is now possible to directly probe the atomic structure and observe phase transitions in real time under dynamic loading at ~10 nanosecond timescales. This talk will summarize selected results from recent studies at the Omega Laser and the National Ignition Facility (NIF). At Omega and NIF, X-ray diffraction experiments have been conducted over the range from 0.1-1 terapascals on oxides (GeO2, SnO2), silicates (Mg2SiO4), and carbides (SiC), providing new constraints on crystal structures, equations of state, phase transitions, and kinetics at extreme conditions. The results have applications to understanding the deep interior of the Earth and rocky exoplanets.
March 3, 2022
Inertial Fusion Energy (IFE): Plans and Progress for Reestablishing a National Program

Tammy Ma
Lawrence Livermore National Laboratory
Developing an economically attractive approach to fusion energy is a grand scientific and engineering challenge. Fusion has the potential to provide clean, limitless, reliable energy, that can not only help address the urgent issue of climate change, but can also provide energy sovereignty and security for the U.S. With the recent game-changing results on the NIF, and our decades of expertise in inertial fusion science and technology, the U.S. is well-poised to lead and capitalize on the potential of inertial fusion. However, there is currently no IFE program in the U.S., and it is not part of the long-term energy R&D portfolio. This talk will survey the history of IFE research and funding in the US, review current efforts and plans to re-establish a national program, and discuss the role that LLNL can play. We will also go over some of the science and technology requirements for the realization of IFE and highlight a number of promising technologies key to eventual IFE systems that are already making steady progress.
February 17, 2022
Light-source diffraction studies of phase transitions under shock loading and release

Sally June Tracy
Carnegie Institution for Science
New facilities that couple dynamic loading platforms with high-flux X-ray sources allow for in situ X-ray diffraction under shock compression. Such experiments can address long-standing questions concerning the stable crystallographic phases under rapid loading and release and reveal mechanistic details of shock-induced transformations. This talk will review recent XFEL and synchrotron diffraction studies of carbonates, silicates, and oxides under laser-based and gas-gun shock compression and discuss applications of these results to geophysics and materials science. These studies demonstrate that complex high-pressure phase transitions can be explored on nanosecond timescales, improving our understanding of the dynamic response of materials under extreme conditions.
February 3, 2022
Can two ultra-intense laser pulses accelerate protons better than one with the same total energy?

Christopher Orban
Ohio State University
Ultra-intense lasers are a promising source of energetic ions for various scientific, engineering and biomedical applications. An approach to enhancing both the numbers and energies of protons that has been relatively unexplored is to irradiate a thin target with two ultra-intense laser pulses simultaneously. Particle-In-Cell simulations suggest that this technique could potentially double the numbers and energies of protons (Ferri et al 2019, 2020). The spatial and temporal alignment needed to produce this enhancement is a considerable experimental challenge. In a recent paper from my group, we explore in simulations how robust this result may be to experimental conditions (Rahman et al 2021). We also worked to obtain insights into the physics of why this enhancement occurs. These results should be helpful in demonstrating the enhancement experimentally.
January 20, 2022

Niaz Abdolrahim
University of Rochester
At extraordinary high pressures, like those at the inner core of earth, materials can undergo extreme real-time structural changes. New phase nucleation/transformation processes take less than 10-9 and in some cases 10-12 seconds making it challenging to study by conventional pump-probe measurements due to temporal and spatial limitations. Understanding phase transition mechanisms of material and chemical systems is important for identifying new pathways of forming new matter with desired properties and behavior at extreme conditions. We propose to explore the multiscale nature of matter from atomic to the macro-scale, connecting experimental observations with atomistic simulations and deep learning computer vision techniques to answer key question of how atomic rearrangement through defect motion enables the bulk phase transformations in extreme solids.
In this talk, I present the results of a series of non-equilibrium molecular dynamics simulations to investigate the phase transformation processes of Aluminum under ramp compression loading conditions where it undergoes fcc-hcp-bcc phase transition. I will discuss the agreement in stress-density response between previously laser-driven ramp compression experiments and our simulations by cross-examining the experimental and synthetic x-ray diffraction (XRD) data. I will also discuss our methodology of AI-powered computer vision techniques to automatically learn image features and identify lattice-level mechanisms from large number of XRD data. The proposed framework will be significantly useful in capturing and analyzing new and unknown phenomena in materials under extreme conditions when no prior knowledge is available.
January 13, 2022
Femtosecond X-Ray Diffraction Studies of Shock-Induced Texture Evolution

Justin Wark
University of Oxford
Department of Physics
Clarendon Laboratory & Oxford Center for High Energy Density Science (OxCHEDS)
The coupling of high-power nanosecond optical lasers to FELs has seen a rapid growth in the study of solid-state matter compressed to high pressures via laser-plasma ablation. Femtosecond diffraction of the x-rays during the compression process can give information on the formation of both new phases and the deformation processes that occur. An understanding of the underlying physics is of fundamental interest, as it is the plastic work performed on the sample that largely dictates the final temperatures reached. Furthermore, accurate direct temperature measurements during the compression process are hard to achieve, especially if the target is kept relatively cool (compared with shock compression) via a ramped application of the pressure. Information on the plasticity mechanisms operating at the lattice level can, at least in certain cases, be obtained by monitoring lattice rotation by x-ray diffraction, and from such measurements we can infer which slip systems are active, and to what degree. In this seminar I will discuss several experiments that have taken place over the past few years where such texture evolution has been studied in copper and tantalum samples and show how the results of them are consistent with recent molecular dynamics simulations at the single crystal level, as well as finite element plasticity simulations operating at the mesoscale. I will conclude by commenting on the need to develop in situ temperature measurements, and on the assumptions often made that dynamic compression experiments are of direct relevance to planetary science.
December 6, 2022
Japan Speaker:
Dr. Yuji Fukuda
Kansai Photon Science Institute (KPSI)
National Institutes for Quantum Science and Technology (QST)
“Laser-driven quasi-monoenergetic proton acceleration utilizing micron-scale hydrogen cluster targets”
We introduce a new ion acceleration scheme using prominent characteristics of cluster targets for achieving multi-MeV quasi-monoenergetic proton bunch acceleration. In this scheme, the collisionless shock dynamics inside the micron-scale hydrogen cluster subsequently coupled with relativistically induced transparency (RIT) effect of high-intensity laser plays an important role. This multi-process can be synchronized in a self-consistent manner once conditions for the laser and cluster are satisfied, leading to the quasi-monoenergetic proton bunch acceleration. Here, the result of recent experiments, which demonstrate the quasi-monoenergetic proton bunch acceleration via interaction of micron-scale hydrogen cluster targets with PW-class laser pulses conducted using the J-KAREN-P laser facility at KPSI-QST, will be presented.
US Speaker:
Dr. Jon Belof
Lawrence Livermore National Laboratory
“Phase Kinetics, metastability and compressibility far from equilibriu”
One of the greatest challenges of modern science is the understanding of matter far from equilibrium. Modern techniques of applying rapid compression – via drivers that have relative timescales varying by many orders of magnitude – offer the unique possibility of manipulating kinetic pathways with the goal of generating specific configurations of matter. At LLNL we have been examining the theoretical underpinnings of transformational pathways far from equilibrium, with a focus on the nucleation and growth of potential metastable solid phases from liquid systems. Through advanced simulation techniques developed recently, we have found several interesting features of phase transitions as they occur under extreme conditions, with predictions showing that metastable phases are indeed generated along compression pathways, that they might be stabilized, and suggestions for how new x-ray sources and experimental conditions can be brought to bear on these important, fundamental questions. New scaling laws that predict the observable metastability as a function of compression rate offer possible joint theoretical and experimental investigations toward improving predictive capabilities for high energy density conditions.
November 8, 2022
Japan Speaker:
Professor Youichi Sakawa
Institute of Laser Engineering, Osaka University
“Generation of collision less shocks using high-energy lasers”
Collision less shock is a shock wave generated in a collision less plasma, in which Coulomb collisions are negligible. Wave–particle interactions and collective effects of electric and magnetic fields play essential roles in shock formation. Collision less shock is ubiquitous in space and astrophysical plasmas. In general, we can distinguish collision less shock into three categories: magnetized shock, electromagnetic turbulence sustaining shock (EM shock), and electrostatic shock (ES shock). Magnetized shock is ubiquitous in space and astrophysical plasmas. EM shock is predicted to be mediated by a self-generated turbulent electromagnetic field. The Weibel instability is a leading candidate for the generation mechanism of turbulent electromagnetic fields and shocks. ES shock is rare in the Universe. It may occur even with an external magnetic field under special conditions, such as in the auroral zones, but here we focus only on the cases without an external magnetic field. We present experimental achievements in these three types of collision less shock using high-energy lasers.
US Speaker:
Dr. Richard Kraus
Lawrence Livermore National Laboratory
“Measuring the Melting Curve of Iron at Super-Earth Core Conditions”
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.
September 20, 2022
Japan Speaker:
Professor Yasuhiro Kuramitsu
Graduate School of Engineering, Osaka University
“Particle acceleration in space and laboratory plasma”
Energetic charged particles or cosmic rays are ubiquitous in the Universe, and the origins of cosmic rays have been a long standing open problem more than a century. We have been tackled this using intense lasers in laboratories. In this talk our recent efforts on the experimental investigations of relativistic electron and ion acceleration will be presented. We discuss the nonthermal particle acceleration and the universality of the power law energy spectra of accelerated particles in space and astrophysical contexts and also in laboratories.
US Speaker:
Dr. Ronnie Shepherd
Lawrence Livermore National Laboratory
“Utilizing ultrashort pulse laser heated matter to study fundamental properties of high energy-density plasma”
The properties of high energy-density(HED) matter are central to understanding fields such as stellar evolution, astrophysics, and thermonuclear fusion. Historically, comparing analytic models of HED matter to experimental results have been hampered by spatial and temporal gradients. Ultrashort pulse lasers can heat matter on a time-scale short compared to hydrodynamic expansion times, resulting in a minimal spatial gradient, high temperature, high density plasma for short durations. Additionally, the development of high time resolution diagnostics allows the study of HED matter with minimal spatial and temporal gradients.
We present three experiments that demonstrate the unique capabilities of short pulse lasers to study fundamental properties of HED matter. The first experiment demonstrates a different approach to benchmarking absorption (or opacity) properties of HED matter by measuring emissivity. These experiments are being performed at the Orion laser (~700 fs, 100 J, 5320 nm) facility at the Atomic Weapons Establishment (AWE) in England. The second experiment (also performed at Orion) provides data to study ionization as plasma density increases (pressure ionization or ionization potential depression). The third, and most recent, experiment was performed at the ALEPH laser (45 fs, 8J, 400 nm) at Colorado State University. This experiment takes advantage of ion micro-fields and spectral line shapes to infer the electron-ion equilibration in HED matter. The philosophy of the measurements, data, and current state of analysis will be presented.
August 9, 2022
Japan Speaker:
Professor Shinsuke Fujioka
Institute of Laser Engineering at Osaka University
”Experimental Studies of Hydrodynamic Instabilities for Magnetized Fast Ignition”
Ablative RT instability growth was investigated to elucidate the fundamental physics of thermal conduction suppression in a magnetic field. Experiments found that unstable modulation growth is faster in an external magnetic field. This result is reproduced by a magnetohydrodynamic simulation based on a Babinskii model of electron thermal transport. An external magnetic field reduces the electron thermal conduction across the magnetic field lines because the Larmor radius of the thermal electrons in the field is much shorter than the temperature scale length. Thermal conduction suppression leads to spatially nonuniform pressure and reduced thermal ablative stabilization, increasing the growth of ablative RT instability. We also determine that the strength of the magnetic field can affect the ablative RT instability. The stronger the magnetic field, the higher the modes of RT growth affected. In other words, by reducing the thermal transport at the instability growth front, the magnetization allows higher modes of RT instability to grow.
US Speaker:
Michael MacDonald
Lawrence Livermore National Laboratory
“Developing x-ray fluorescence spectroscopy as a temperature diagnostic for high-energy-density physics experiments"
Electron temperature is a fundamental parameter in plasma physics, affecting many important plasma properties such as ionization, heat transport, and compressibility. Despite its importance, temperature data from experimental measurements in the high energy density (HED) and warm dense matter regime are sparse due to the limited number of diagnostic techniques available for temperatures in the 10s of eV temperature range. This temperature range is particularly difficult to measure in dense plasmas or in experimental geometries with large volumes (e.g. hydrodynamics experiments) due to the fact that the photon energies required for x-ray emission and absorption spectroscopy scale with temperature and x-ray scattering measurements require uniform plasma conditions. To address this need, we are developing x-ray fluorescence spectroscopy (XFS) as a temperature diagnostic for HED plasmas. XFS interrogates the plasma with an external energy source (typically x-rays or electrons) to fluoresce specific ions in a plasma to determine the ionization state distribution, and in turn the plasma temperature. We will present results demonstrating the use of XFS to determine the temperature of shocked foams and initial results from the Gbar platform at the National Ignition Facility.
July 12, 2022
Japan Speaker:
Dr. Mamiko Nishiuchi
Institute of Laser Engineering at Osaka University
“Highly charged energetic ion beam from high temperature high density plasma produced by temporally controlled short-pulse high intensity lasers”
Motivated by the development of next-generation heavy ion accelerators, we have been searching for the efficient ion acceleration scheme by using short-pulse high intensity laser systems. Different from the light ion acceleration, heavy ion acceleration is more difficult because of an additional parameter to be controlled, ionization. Higher the ionization state, higher the acceleration efficiency. However, it is challenging to highly ionize heavy metals, such as gold or silver, as inner shell electrons are bounded in deep potential wells, i.e., a silver atom has an ionization potential Ip > 5 keV for its L-shell and ∼30 keV for its K-shell. The total ionization potential density of solid silver is Pion ∼ 1.3 peta-Pascal (PPa). A petawatt-class laser focused to an intensity I = 10^21 W/cm^2 has an energy density of 33 PPa. If we use petawatt-class laser light as a tool, we can in principle produce highly ionized heavy metal plasmas. We, therefore, used temporally controlled high intensity laser pulse from J-KAREN laser-system at KPSI in Japan, experimentally demonstrated generation of highly charged silver ions (Z∗ = 45±2) with energies of >20MeV/nucleon (>2.2 GeV) from submicron silver targets driven by a laser with intensity 5 × 10^21W/cm^2. By investigating the detail hybrid simulation which reproduced the experiments well, the dominating ionization mechanism for producing highly charged energetic silver ions is clarified to be electron collisional ionization in the ~ 10 KeV high density silver plasma.
US Speaker:
Dr. Toshiki Tajima
Department of Physics and Astronomy
University of California, Irvine
“High-Density Laser Wakefield Acceleration”
Laser wakefield acceleration (LWFA) is capable of accelerating electrons over a compact distance. The recent development of the high density (HD) regime of LWFA allows the relatively low energy electron acceleration over a microscopic distance with higher efficiency [1]. This HD-LWFA introduces new operations and opportunities of radiotherapy by electrons. With one such operations we may take a radiotherapy using the endoscope (LWFA via a fiber laser at its tip, for example), in which a surgeon may look at tissues via endoscope and zap electrons in front of its target inside a patient body. Because of the HD-LWFA (using nanotubes as its critical density target) is so tiny (and also more efficient) than the regular gaseous LWFA, its structure may fit such a tiny confine (and all solid state) operation [2]. The concept of operating efficient laser acceleration near the critical density also applies to laser ion accelerator [3].
[1] E. Barraza, T. Tajima, D. Strickland, and D. Roa, accepted by Photonics (2022)
[2] D. Roa et al., Photonics 9, 403 (2022)
[3] A. Necas, et al., Photonics 9, 434 (2022)
June 14, 2022
Japan Speaker:
Professor Masahiro Hoshino
School of Science, The University of Tokyo
“Efficiency of Particle Acceleration in Magnetic Reconnection”
Magnetic reconnection is a ubiquitous process not only in non-relativistic plasmas such as solar flares and tokamak discharge disruptions, but also in relativistic plasmas such as pulsars and black hole magnetospheres, and it has become necessary to understand the physics of reconnection from non-relativistic to relativistic plasmas seamlessly. In this context, it is desired to realize relativistic reconnection in the laboratory, as a laser plasma experiment is expected to access a relativistic reconnection regime by producing strong magnetic fields. In this talk, we focus on the energy partition between thermal and nonthermal particles as an interdisciplinary research topic of reconnection. We investigated both non-relativistic and relativistic magnetic reconnections by using PIC simulation for a pair plasma and found that the production of the nonthermal particle becomes efficient with increasing the Alfven speed. While the thermal energy density dominates for the non-relativistic reconnection, the nonthermal energy density becomes over 95% of the total internal energy in the downstream exhaust for the relativistic reconnection.
US Speaker:
Dr. Scott Wilks
Lawrence Livermore National Laboratory
“The Long and the Short of it: How advances in short pulse laser technology influence our understanding of laser plasma interactions in HED Physics”
The development of Petawatt-class short pulse laser technology has made it possible to create some of the brightest sources of particles and photons on the planet, albeit at low average power. These high peak power lasers enable sub-nanosecond photon, proton, and neutron radiographic snapshots of dense solids and plasmas, as well as their associated electric and magnetic fields, with near-micron spatial resolution, with the additional ability to create high energy density plasmas via isochoric heating. In this seminar, we show how two specific laser developments are influencing how we think about relativistic laser plasma interactions. First, we discuss how the development of kilojoule class “long” short pulses (from 1 to 20 ps in duration) with large spots (~ 50 micron) made us rethink some of the fundamental electron acceleration mechanisms that underlie short pulse laser matter interactions, and how this is helping us improve these radiographic sources for HED experiments. Next, we will see how the development of new “short” (from 100 fs to 1 ps) pulse lasers with high average powers as high as 300 kW are forcing us to examine the impact of laser wavelength on our current radiographic sources, while at the same time opening the door to completely new applications that are currently exclusively handled by high average power particle accelerators. These new applications include novel methods for measuring nuclear cross sections, nuclear waste transmutation, and short pulse-based ignition methods for Inertial Confinement Fusion.
May 10, 2022
Japan Speaker:
Professor Takuo Okuchi
Institute for Integrated Radiation and Nuclear Science, Kyoto University
“Structure transformation of silicate minerals during hypervelocity collisions occurred in the solar system”
Meteorites from interplanetary space often involve dense structural polymorphs of silicate minerals as records of past hypervelocity collisions. These dense high-pressure minerals, including recently discovered species by ourselves, were all kept frozen for billions of years after experiencing the collisions. Therefore, they potentially provide us invaluable information on the history of the solar system evolution. We recently discovered the origin of one of such dense minerals by laboratory experiments, using a focused high-power laser pulse coupled with femtosecond diffractometry using an X-ray free electron laser pulse. Our results show that the structure transformation occurs through a ultrafast crystal-lattice-shearing process. We consider that such process were frequently triggered in the solar system to have frequently produced the dense minerals within a wide variety of planetary materials.
US Speaker:
Dr. Annie Kritcher
Lawrence Livermore National Laboratory
“Inertial confinement fusion experiments at the NIF reaching the burning plasma regime, 1.37 MJ, and the Lawson criterion for ignition”
The inertial fusion community have been working towards a burning-plasma and ignition for decades, since the idea of inertial confinement fusion (ICF) was first proposed by Nuckolls, et al., in 1972. In 2020-2021 a burning plasma was first reached and on August 8, 2021, the Lawson criterion for ignition was finally demonstrated in the laboratory on the National Ignition Facility (NIF) in Northern California. When the extra heating from alpha particles exceeds the heating required to initiate the fusion reactions the plasma is in a "burning plasma" state and when the alpha particle heating is greater than the initial work done on the plasma as well as the energy loss mechanisms, and for a long enough duration of time, the plasma "ignites". Experiment N210808 produced a fusion yield of 1.37 MJ from 1.9 MJ of laser energy and appears to have crossed the tipping-point of thermodynamic instability according to several ignition metrics. The “indirect” ICF approach at NIF described in this talk uses a hohlraum radiation cavity to heat and ablate the outside of a capsule that contains Deuterium-Tritium (DT) fusion fuel. This ablation causes the fuel to accelerate inward (implode) at high velocities doing work on a central lower density “hot spot” of DT fuel, increasing the temperature and density of the hot spot to the extreme conditions required for fusion. This presentation discusses the development of a platform that increased the hot-spot energy and hot-spot pressure, to achieve record ICF performance.
April 5, 2022
Japan Speaker:
Dr. James Kog
QST Research Scientist
“Possible precision measurements of Delbrück scattering with high flux polarized gamma-ray sources"
Quantum electrodynamics (QED), which describes the interaction of photons with electrons, has been tested experimentally and found to agree with experiments to high precision to lowest order. However, higher order measurements are required to test QED. Delbrück scattering is a higher order process, which involves the scattering of photons off the Coulomb fields of nuclei and is the only one which has been measured due to its large cross section. We have found recently that polarized gamma ray sources can achieve high precision measurements of Delbrück scattering. Currently, there are many petawatt-class laser facilities operating, being constructed, and planned around the world. Such laser systems can produce extremely high flux highly polarized gamma rays in laser-plasma, electron beam-laser interactions. Therefore, they have the possibility of measuring Delbrück scattering to high precision. We believe this will be of great interest to the plasma and fusion research community at large.
US Speaker:
Professor Burkhard Militze
Department of Earth and Planetary Science, University of California, Berkeley
“First-Principles Equation of State (FPEOS) Database for Warm Dense Matter Computations”
This talk will focus on computer simulations of matter at extreme conditions and compare with on-going experimental work. We will discuss our publicly available first-principles equation of state (FPEOS) database for matter at extreme conditions that we put together by combining results from path integral Monte Carlo and density functional molecular dynamics simulations [1]. We provide our equation of state (EOS) tables for the elements H, He, B, C, N, O, Ne, Na, Mg, Al, and Si as well as the compounds LiF, B4C, BN, CH4, CH2, C2H3, CH, C2H, MgO, and MgSiO3. For all these materials, pressure and internal energy are provided over a wide density-temperature range from 0.5 to 50 g/cc and from 105 to 109 K. Results from 5000 first-principles simulations were combined. In this talk, we focus on isobars, adiabats and shock Hugoniot curves of different silicates in the regime of L and K shell ionization. Starting from the EOS tables of the individual elements and compounds, we invoke the linear mixing approximation [2] to predict the shock properties of arbitrary binary and ternary mixture. We compare with experimental results for H2O, CO2, and CH.
March 22, 2022
Japan Speaker:
Professor Natsumi Iwata
Institute of Laser Engineering at Osaka University
Kilojoule class petawatt lasers enable relativistic light irradiation over picoseconds (ps) with large focal spots. Such lasers open up access to a new regime of high energy density plasma physics where non-equilibrium plasma forms quasi-stationary structures in the open system. In this regime, mesoscale phenomena between the kinetic and fluid scales are important. Electron acceleration becomes efficient by stochastic accelerations in the plasma blowing off at high pressure toward the laser in ps time scales. The achievable energy density also becomes higher due to a self-confinement of electrons by random field scattering and a fast diffusive heating from the hot preplasma.
US Speaker:
Dr. Arianna E. Gleason
SLAC / Stanford University
“Frontier of Dynamic Materials Research Using Ultrafast X-rays”
The study of matter under extreme conditions is a highly interdisciplinary subject with broad applications to materials science, plasma physics, geophysics and astrophysics. Understanding the processes which dictate physical properties in warm dense plasmas and condensed matter, requires studies at the relevant length-scales (e.g., interatomic spacing) and time-scales (e.g., phonon period). Experiments performed at XFEL light sources across the world, combined with dynamic compression, provide ever-improving spatial- and temporal-fidelity to push the frontier. This talk will cover a very broad range of conditions, and give examples of case-studies closely related to geophysics, Astro(bio)physics, planetary-, and fusion energy-sciences, as enabled by microstructure visualization and control from in situ, ultrafast X-ray diffraction and imaging. Two case studies will be discussed: 1) an examination of crystal plasticity and strength of shock-compressed hcp-iron to ~200 GPa, and 2) void collapse physics in ICF ablator materials.
February 15, 2022
Japan Speaker:
Professor Hitoki Yoneda
The Institute for Laser Science at the University of Electro-Communications in Tokyo
“Coherent control of hard x ray laser”
US Speaker:
Dr. Didier Saumon
Los Alamos National Laboratory
“Scratching below the surface of white dwarf stars: EOS measurements at unprecedented pressures"
January 11, 2022
Japan Speaker:
Professor Kiminori Kondo
Kansai Photon Science Institute (KPSI)
“Laser-driven ion acceleration and its medical application in Kansai Photon Science Institute (KPSI)”
US Speaker:
Professor Farhat Beg
University of California, San Diego
“Proton Fast Ignition; Past Present and Future”
December 16, 2021
Debra Callahan
Lawrence Livermore National Laboratory
One of the scientific milestones in fusion research on the path to ignition is creating a burning plasma. A burning plasma occurs when the energy deposited by the fusion-produced alpha particles is the dominant source of heating of the plasma – this is a necessary step to reach ignition. Over the last year, experiments on the NIF laser have reached this state using two indirect-drive designs; these two designs use larger capsules than had been used previously while maintaining the other important parameters of implosion velocity, low-mode symmetry, late-time ablation pressure, and high Z mix. To drive larger capsules with the same amount of laser energy, the larger capsules had to be driven in a similar size hohlraum, which makes maintaining a symmetric drive more difficult, and required the use of additional techniques to mitigate low-mode asymmetry.
One of these designs, Hybrid E, has also achieved ignition by the Lawson criterion. Under that definition of ignition, the fusion-produced alpha heating dominates the power balance in the hotspot – overcoming radiative and conduction losses. The experiment on Aug 8, produced 1.35 MJ, which is a capsule gain (yield/capsule absorbed energy) of about 6x. The target gain, yield/laser energy, was 0.7 – which did not meet the NAS definition of ignition = gain 1. This design is likely on the ignition cliff, which means it is in a sensitive part of parameter space – repeat experiments to date have all achieved capsule gain > 1 but with lower yields than the August experiment.
Since the start of experiments on NIF, progress has been made in steps. At each step, a combination of experimental data (including improved diagnostics), theory, and modeling is used to identify and understand the limiters in performance. New designs are then developed using this understanding – this generally results in an increase in performance until the next limiter becomes dominant. This cycle has produced several physics milestones on the way to ignition. First was fuel gain, where the neutron yield exceeds the energy in the deuterium-tritium (DT) fuel [1]. Next was “alpha heating,” in which the neutron yield is doubled due to the additional energy deposited in the DT fuel by alpha particle stopping [2,3]. Now, we have achieved the burning plasma state [4]. In this talk, we will review these new designs and experiments and show how the August experiment compares with several published ignition metrics.
[1] O. A. Hurricane, et al., Nature 506, 343 (2014)
[2] S. Le Pape, et al., Phys. Rev. Lett. 120, 245003 (2018)
[3] D. T. Casey, et al., Phys. Plasmas 25, 056308 (2018)
[4] A. B. Zylstra, O. A. Hurricane, et al. accepted for publication
*Work performed under the auspices of the U. S. Department of Energy by LLNL under contract DE-AC52-07NA27344
Direct measurements of temperature and phase transitions along the MgO shock Hugoniot
December 2, 2021

June Wicks
John Hopkins University
Laser-driven shock compression enables experimental study of material properties at unprecedented pressures and temperatures. Experiments that probe these extreme conditions are conducted at timescales approaching the limits of atomic mobility, convoluting kinetic effects into observations of phase transitions. In this talk, I will present a suite of studies of the MgO Hugoniot aimed at constraining the phase diagram, comparing effects of crystallographic orientation, timescale (decaying vs steady shocks), and x-ray vs pyrometry diagnostics. I will discuss the implications of this work for our understanding of phase transitions under dynamic compression and our ability to experimentally extricate thermodynamics from dynamics.
Generating burning plasmas with improved implosions in the Hybrid-E platform
November 18, 2021

Alex Zylstra
Lawrence Livermore National Laboratory
Improving the performance of implosions on NIF by increasing the energy coupled to the capsule has been a strategy pursued in the last several years. The main challenge in improving the energy coupling is in increasing the hohlraum efficiency while maintaining both control over the radiation drive symmetry and key implosion parameters, such as the implosion velocity and coast time. Improved hohlraum efficiency with symmetry control was recently demonstrated in the ‘Hybrid E’ platform [1], which introduces a small amount of wavelength detuning (Dl) to alter the amount of cross-beam energy transfer and increase drive on the hohlraum waist. Recent work has increased the velocity and increased the late-time ablation pressure as the capsule implodes, both of which lead to large increases in stagnation pressure and implosion performance, with the yield tripling from earlier results. These implosions have now entered the burning plasma regime [2-4], with Qa ~ 1.5. A detailed comparison of the increased stagnation pressure with these key design parameters, and expected scaling relations, will be discussed to guide the path forward towards even higher implosion performance.
[1] A.B. Zylstra et al., Phys. Rev. Lett. 126, 025001 (2021) [2] A.B. Zylstra, O.A. Hurricane, et al., submitted to Nature (2021) [3] J.S. Ross, J.E. Ralph, A.B. Zylstra, et al., submitted to Nature Physics (2021) [4] A.L. Kritcher, C.V. Young, H.F. Robey, et al., submitted to Nature Physics (2021).
This work was performed under the auspices of the U. S. Department of Energy by LLNL under contract DEAC52-07NA27344. LLNL-ABS-82291.
November 18, 2021

Omar Hurricane
Lawrence Livermore National Laboratory
Conventional belief in inertial confinement fusion (ICF) is that high laser power and low DT fuel adiabats are required for obtaining ignition. The textbooks in ICF make no mention of the concept of “coast-time,” yet implosion experiments on the NIF have repeatedly shown better success with higher adiabat designs driven to very short coast-times. Understanding why took time. Reduced coast-time (the time between peak ablation pressure and implosion bang-time) is important for maintaining shell compression and high stagnation pressure [1]. Theory [2] has recently revealed that coast-time has a subtle connection to the radius at which peak velocity (Rpv) is achieved. Reduced Rpv can compensate for high fuel adiabat and allow access to exceedingly high stagnation pressures. The ignition relevant metric EP2 (where E is hot-spot energy and P is hot-spot pressure) is exceedingly sensitive to Rpv, indicating that even relatively small decreases in Rpv can rapidly push an implosion towards igniting. This understanding was key to moving the Hybrid-E [3,4] implosion into the burning plasma regime [5], and now, to the scientific ignition threshold with a fusion yield of 1.35 MJ and capsule gain of >5 on August 8, 2021. In this talk, we tell the story of how we pieced together puzzling observations and theory of this obscure, but critical bit of ICF physics over a period of 8 years.
[1] O.A. Hurricane, et al., Phys. Plasmas, 24, 092706 (2017) [2] O.A. Hurricane, et al., Phys. Plasmas submitted, (2021) [3] A.L. Kritcher, et al., Phys. Plasmas, 28, 072706 (2021) [4] A.B. Zylstra, et al., PRL, 126, 025001 (2020) [5] A.B. Zylstra, O. A. Hurricane, et al. in preparation (2021).
This work was performed under the auspices of the U. S. Department of Energy by LLNL under contract DE-AC52-07NA27344. Sorting Category: 07.06.
Multiphase EOS development at LLNL and application to a wide-ranged semi-empirical multiphase EOS for iron
November 4, 2021

Christine Wu
Lawrence Livermore National Laboratory
An equation of state (EOS) plays a key role in encapsulating state-of-the-art scientific advances into a set of physical models that can then be utilized by hydrodynamics simulations to improve their predictive capability. In this talk, we first give a brief update on the status of multiphase EOS development at LLNL. We then illustrate this development methodology by describing the construction of a wide-ranged multiphase EOS for elemental iron (Fe), consisting of five phases: α (bcc), ε (hcp), γ (fcc), δ (high-T/low-P bcc), and liquid. The free-energy models for the phases are constrained by fitting to experimental data in both lower-pressure and high-pressure regimes, and to the predictions of ab initio electronic-structure calculations at higher pressures and temperatures. We show that our resulting multiphase Fe EOS is in excellent agreement with a diverse range of static and dynamic high-pressure experimental data, and in many cases provides substantially better agreement than other currently used multiphase Fe EOS models. It should thus enable more accurate predictions of complex high-P,T processes involving Fe and Fe alloys in a host of high-energy-density physics problems, including those of great interest to planetary science.
Enabling high repetition rate laser wakefield acceleration at high and low plasma densities
October 28, 2021

Howard M. Milchberg
Lawrence Livermore National Laboratory
Recently, we have achieved record all-optical laser wakefield acceleration results at opposite ends of the laser energy and plasma density ranges. Using < 3 mJ/ pulse at 1 kHz and near- critical density, 100-micron thick plasmas, we have produced low divergence, 15 MeV quasi-monoenergetic electron bunches. At three to four orders of magnitude lower plasma density, we have generated bunches up to 5 GeV by injecting and guiding 13 J pulses in meter-scale plasma waveguides. I will describe these experiments and what led up to them.
Stellar-Relevant Emission-Based Opacity Experiments at the Orion Laser Facility
October 21, 2021

Madison E. Martin
Lawrence Livermore National Laboratory
Short-pulse laser facilities, such as the Orion Laser Facility, can be used to directly heat targets to conditions consistent with the radiative zone of the sun, enabling the measurement of x-ray emission which can be used to infer opacity of materials at extreme conditions. Opacity is a critical parameter in the transport of radiation in high energy density (HED) systems such as inertial confinement fusion capsules and stars. The resolution of current disagreements between solar models and helioseismologically observations would benefit from experimental validation of theoretical opacity models. As a complement to existing platforms using long pulse lasers (ex. the National Ignition Facility) and pulsed power machines (ex. the Z Machine), short pulse lasers can be used to heat targets to even higher temperatures and densities. Time-integrated and time-resolved spectra of iron were measured at the Orion short-pulse laser. The K-shell spectra of sulfur, potassium, and chlorine were measured and used to diagnose the plasma conditions. We will discuss two main modeling approaches used to simulate spectra for comparison with measured spectral data: 1.) ray trace of 1-dimensional (1D) radiation-hydrodynamic models and 2.) stand-alone spectral calculations employing more sophisticated atomic physics. We show that while our 1D radiation-hydrodynamic methodology has been useful for predicting and matching many aspects of the experimental spectra, this simplified method does not create a consistent picture for all materials in the experiment. We therefore introduce future improvements to the methodology that may aid in understanding sensitivities of our emission-based opacity platform.
The High Energy Density Science Center: 2021 year in review
October 7, 2021

Frank Graziani
Lawrence Livermore National Laboratory
High Energy Density Science Center Director
The High Energy Density Science Center (HEDSC) was established in late 2015 through a joint agreement between the Physical and Life Sciences, Weapons and Complex Integration, and NIF and Photon Science directorates. The Center’s goal is to build a high energy density community through support of, and collaboration with, academic partners and to integrate those efforts with the programs at LLNL. The Center is built around four focus areas: (1) education, (2) outreach through workshops and seminars, (3) workforce pipeline to the programs, and (4) enabling research collaborations between LLNL and academic partners. In this talk, we will present the year FY21 in review and look at what lies ahead in FY22. FY21 saw continuation in education programs with a new version of a quarter long course on HED diagnostics offered in collaboration with UCSD and featuring new distance learning technology and guest lecturers. In addition, the HED center education program is working with WCI to help offer training for new designers. Another new HEDS Center Fellow was selected and our current HEDS Center Fellow, Andrew Longman, completed his first year. Besides educating the next generation of HED scientists, the HEDS Center continues training students through internships and thesis opportunities. Our outreach and collaboration activities continue through a vibrant seminar series, university partnerships, a sabbatical program, and visits to community colleges and undergraduate institutions. Inclusion and diversity are an important aspect of our mission and the Consortium for HEDS (FAMU, UC Merced, Morehouse and LLNL) and the Center help a number of students within HEDS. The Consortium’s goal is to provide research and education opportunities in HEDS for under-represented groups and thereby increase diversity in the field. Under the restrictions of the pandemic, the summer internship program continued, on-line. The sabbatical program has now started after a hiatus in FY21. In FY22 we hope to expand the sabbatical program and begin outreach visits to K-12 and community and undergraduate colleges. A call for a new HEDS Fellow postdoc position is out and more HED education programs are planned. In FY22 we will continue to foster international collaborations in HEDS, supporting another thesis student from FAMU, as one finishes, and continue the internship program.
Thermonuclear Fusion in an Equilibrium Z Pinch
September 23, 2021

Uri Shumlak
University of Washington
The equilibrium Z pinch is a unique approach to magnetic confinement fusion that requires no external magnetic field coils. Equilibrium conditions are reached through the use of sheared plasma flows, which enhance stability and provide a path to thermonuclear fusion. Simple geometry and strong scaling of fusion gain with pinch current form the cornerstones of this compact fusion device. The sheared-flow-stabilized Z pinch has been developed through integrated computational and experimental investigations at the University of Washington in collaboration with Lawrence Livermore National Laboratory. Experimental results demonstrate plasma stabilization, sustained thermonuclear fusion, and agreement with theoretical and computational predictions. Building on these advances, Zap Energy Inc. is developing a low-cost fusion reactor core based on the equilibrium Z pinch.
Low-velocity proton stopping power measurement in Warm Dense Matter
August 26, 2021
Sophia Malko
Princeton Plasma Physics Laboratory
Ion stopping in warm dense matter is a process of fundamental importance for the understanding of the properties of dense plasmas, the realization and the interpretation of experiments involving ion-beam heated warm dense matter samples, and for inertial confinement fusion research. The theoretical description of the ion stopping power in warm dense matter is difficult, notably due to electron coupling and degeneracy, and measurements are still largely missing. In particular, the low-velocity stopping range around the Bragg peak, that features the largest modelling uncertainties, remains virtually unexplored. We present proton energy loss measurements in warm dense plasma at lower projectile velocities than previous experiments, coming significantly closer to the Bragg-peak region. Our energy loss data, combined with a precise target characterization based on plasma emission measurements using two independent spectroscopy diagnostics, demonstrate a significant deviation of the stopping power from classical models in this regime. In particular, we show that our results are consistent with recent first-principles simulations based on time-dependent density functional theory.
Using quantum computers to simulate a toy problem of laser-plasma interactions
August 5, 2021

Yuan Shi
Lawrence Livermore National Laboratory
Quantum computing may lead to game-changing capabilities for science and technology. However, many practical problems are classical, and exactly how quantum systems can be used to solve classical problems remains an open question. Moreover, for plasma physics, many problems are nonlinear, whereas quantum computers are designed to carry out unitary evolution in Hilbert spaces, which are fundamentally linear. In this seminar, I will present the first results using real quantum hardware to simulate a toy problem that is relevant to laser-plasma interactions. A generally applicable algorithm is derived, which encode three-wave interactions on quantum hardware. The algorithm is implemented using two compilation approaches. First, each simulation step is compiled as a sequence of standard gates. Using this approach, ~10 simulation steps can be carried out before results are corrupted by decoherence. Second, each simulation step is compiled as a single customized gate, which is realized using optimal control. Using this approach, the simulation depth is extended to ~100. Our results highlight the advantage of using customized gates on noisy intermediate-scale quantum computers. The generalized nonlinear gates are potentially useful building blocks for solving a large class of problems in plasma/fluid dynamics, nonlinear optics, and lattice gauge theories on quantum computers.
Quantitative Studies of Supersonic Microparticle Impacts on Metals
July 29, 2021

Christopher Schuh
Department of Materials Science and Engineering, MIT
When a microparticle projectile strikes a metal, the resulting physical phenomena that occur are diverse and depend significantly upon the particle velocity. Plasticity sets on at very low velocities, and follows a scaling law whereby the plastically-damped energy rises with velocity. Analysis of this scaling law, through direct measurement of the damped energy itself, can provide quantitative measurements of the prevailing strength of the metal at rates up to and even beyond 108 s-1. At higher velocities, new phenomena set on which disrupt this scaling law. In many metals, hydrodynamic jetting flow occurs beyond a certain critical velocity, leading to a solid-state splash that dissipates extra energy. This jetting involves significant local deformation at the particle surface, and is associated with rupture and flaking of the native oxide layer and the formation of metallic bonds when both impactor and substrate are metals. In other cases, plastic dissipation can lead to enough adiabatic heat production to cause local melting, which is also associated with shifts in the observed energy-velocity scaling law. Finally, when combined with post-mortem analysis of impact sites, such studies can lead to new insights on microstructure evolution within the metal, including the development of nanotwins and nanostructures uniquely associated with high-rate, high-strain deformation.
Relativistically Transparent Magnetic Filaments: a short-pulse platform for megaTesla fields, direct electron acceleration, and efficient gamma radiation
July 22, 2021

Hans Rinderknecht
University of Rochester
Laboratory for Laser Energetics
In relativistically transparent interactions, lasers with intensity above 1020 W/cm2 drive relativistic current filaments in classically overdense plasmas, producing an azimuthal magnetic field that is comparable in strength to the laser field. This magnetic filament traps electrons, which are directly accelerated by the laser pulse to 100’s of MeV and efficiently radiate MeV-scale photons by synchrotron radiation. This seminar introduces this novel process, presents scaling laws that describe the radiated photon energy and radiation efficiency, and shows the results of initial experiments performed at the Texas Petawatt Laser (TPW). The analytical scaling laws are validated by 3-D particle-in-cell simulations in two regimes of focal radius. The efficiency of gamma radiation is predicted to exceed 10% for optimized designs with laser intensity above 6×1021 W/cm2. Experiments at TPW using moderate laser intensity (1021 W/cm2) demonstrate the predicted signatures of electron acceleration and x-ray radiation from a subset of microchannel targets filled with low-density CH foam. This ultrafast photon source may be optimized for a wide range of applications in HED, nuclear, and high-field physics.
Laser-driven magnetic filaments as a platform for high-field science
July 15, 2021

Alexey Arefiev
University of California, San Diego
High-power high-intensity multi-beam laser systems that are becoming operational around the world can now be used to create a platform for high-field science that is based on relativistically transparent magnetic filaments driven by irradiating lasers within a dense plasma. The strength of the quasistatic field can be comparable to that of the laser, reaching the megatesla level. This talk will review several phenomena that can be studied with experimentally achievable laser intensities at multi-PW laser facilities. These include emission of dense gamma-ray beams in the quantum regime and electron-positron pair creation from light alone. Astrophysical environments are known for exotic physics regimes that involve generation of extreme magnetic fields and creation of matter and antimatter from light alone. The discussed platform provides a potential path towards recreating relevant regimes in laboratory conditions.
Frontier of Dynamic Materials Using Ultrafast X-ray Radiography
July 1, 2021

Arianna E. Gleason-Holbrook
SLAC – National Accelerator Laboratory
Standford University
The study of matter under extreme conditions is a highly interdisciplinary subject with broad applications to materials science, plasma physics, geophysics and astrophysics. Understanding the processes which dictate physical properties in warm dense plasmas and condensed matter, requires studies at the relevant length-scales (e.g., interatomic spacing) and time-scales (e.g., phonon period). Experiments performed at XFEL light sources across the world, combined with dynamic compression, provide ever-improving spatial- and temporal-fidelity to push the frontier. This talk will cover a very broad range of conditions, and give examples of case-studies closely related to geophysics, Astro(bio)physics, planetary-, and fusion energy-sciences, as enabled by microstructure visualization and control from in situ, ultrafast X-ray imaging.
Experimental Observations of Laser-Driven Tin Ejecta Microjet Interactions
June 24, 2021

Alison Saunders
Lawrence Livermore National Laboratory
The study of high-velocity particle-laden flow interactions is of importance for the understanding of a wide range of natural phenomena, ranging from planetary formation to cloud interactions. However, given the difficulty of generating high-velocity flows of many particles, experimental observations of particle dynamics under such conditions are sparse. The interactions of ejecta microjets offer a novel experimental mechanism to study particle interactions, as ejecta microjets are micron-scale jets formed by strong shocks interacting with imprinted surfaces to generate particle plumes traveling at several kilometers per second. We recently performed experiments on the OMEGA and OMEGA EP lasers to take the first time-sequences of x-ray radiography images of two interacting tin ejecta microjets. We observe different jet morphologies and characteristics, such as densities and velocities, for different tin shock pressures of 11.7 and 116.0 GPa. But most strikingly, we observe different interaction behaviors as a function of pressure, ranging from jets passing through each other unattenuated to jets generating a corona of material around the point of interaction. We perform simulations of particle collisions to model the interactions and propose future experiments to understand the effects dominating the observed interaction dynamics.
LLNL-ABS-823558. This work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344 and supported by Laboratory Directed Research and Development (LDRD) Grant No. 18-ERD-060.
Relativistic plasma mirrors for high-power ultrashort pulses from UV to soft x-rays
June 3, 2021

Julia Mikhailova
Princeton University
Plasma optics have emerged as an attractive toolkit to manipulate high-intensity light. Relativistic plasma mirrors can generate high-order harmonics of petawatt lasers with theoretical energy-conversion efficiencies exceeding 60%. This seminar will provide an overview of our work revealing the fundamental processes behind the efficient frequency up-conversion by plasma mirrors. We will discuss our recent experiments in which we have generated high-order harmonics in the relativistic regime using the laser beams from our 20-terawatt, 25-femtosecond-pulsed system focused onto solid targets. We will further examine remaining challenges in experimental methods and opportunities relating to driving waveform optimization.
Wide Ranging Ionic Transport Coefficients for High-Energy-Density Applications
May 27, 2021

Luke Stanek
Department of Computational Mathematics, Science and Engineering
Michigan State University
Hydrodynamic models rely on closures via equations of state and transport coefficients. Due to the lack of experimental data for transport coefficients, we heavily rely on molecular dynamics simulations. The key input to these simulations is the force law, the choice of which can vary the computational cost by orders of magnitude.
In this talk, we discuss two complementary approaches: determining a computationally efficient, yet acceptable force law, and optimally using sparse transport coefficient data. We delineated the accuracy boundary of force laws by extracting force-matched pair-interaction potentials from Kohn-Sham molecular dynamics data. These pair-interaction potentials reduce the amount of computational resource needed by orders of magnitude allowing for large-scale simulations. Our results rule out the need for three-body potentials above specific element dependent temperatures. These conclusions highlight that accurate results can be obtained in different regimes using disparate methods. We discuss how machine learning provides an avenue to accurately predict transport coefficients with sparse data spanning these regimes. Moreover, we utilize transport coefficient data from computationally cheap models to predict computationally expensive transport coefficients. Portions of this work were supported by SNL. SNL is managed and operated by NTESS under DOE NNSA contract DE-NA0003525.
Direct Imaging of Extrasolar Planets
May 13, 2021

Bruce Macintosh
Kavli Institute for Particle Astrophysics and Cosmology
Department of Physics, Stanford University
More 4,000 extrasolar planets are now known, but almost all have been detected through indirect methods—measuring the parent star’s Doppler shift or brightness variations. Direct detection refers to spatially separating the planet’s light from that of the star. It is extremely challenging—Jupiter in our solar system is 10^-9 the luminosity of the sun—but allows observations of planets inaccessible to other methods, particularly the outer parts of target systems, and allows spectral a characterization of a planet’s atmospheric properties.
I will discuss the optical physics that makes direct detection challenging, and the techniques—adaptive optics, coronagraphy, and image processing –that can overcome these challenges. To date, direct detection has been successful for young Jupiter-like planets, and I will show highlights of those discoveries, including those from the LLNL-led Gemini Planet Imager.
First-Principles Equation of State (FPEOS) Database And Dilute Cores in Giant Planets
May 6, 2021

Burkard Militzer
Department of Earth and Planetary Science, University of California, Berkeley
This talk will discuss two equation of state applications. First, we will describe a first-principles equation of state (FPEOS) database for matter at extreme conditions that we put together by combining results from path integral Monte Carlo and density functional molecular dynamics simulations of eleven elements and ten compounds [1]. For all these materials, pressure and internal energy are provided over a wide density-temperature range from 0.5 to 50 g/cc and from 105 to 109 K. Results from 5000 first-principles simulations were combined. In this talk, we focus on isobars, adiabats and shock Hugoniot curves of different silicates in the regime of L and K shell ionization. Second, we will discuss how uncertainties in the equation of state of hydrogen-helium mixtures affect our understanding of giant planets. We will review the gravity measurements of the Juno spacecraft that has been in orbit about Jupiter since 2016. Interpreting these measurements has been a challenge because it is difficult to reconcile the unexpectedly small magnitudes of the moments J4 and J6 with conventional interior models that assume an ab initio equations of state as well as a compact core of ice and rock. We conclude by discussing models for Jupiter’s interior that include cores that have been substantially diluted with hydrogen and helium.
Simultaneous measurements of concentration and velocity fields at a shock-accelerated gas interface
April 29, 2021

Riccardo Bonazza
Department of Engineering Physics, University of Wisconsin-Madison
The Richtmyer-Meshkov instability (RMI) develops upon impulsive acceleration of the interface between fluids of different acoustic impedance. The RMI consists in the unbounded growth of any perturbations initially present on the interface, and it is a consequence of the baroclinical deposition of vorticity on the interface. Eventually, the interface develops into a turbulent layer leading to the mixing of the two fluids. Flows of this type occur in nature and in man-made settings, over very large ranges of length, time, and energy scales: from experiments for the attainment of inertial confinement fusion (ICF), to supersonic combustion systems, to supernovae explosions. Shock-induced mixing has very negative effects in the case of ICF while it holds great potential to improve the combustion processes in the case of hypersonic engines. Two of the fundamental parameters that govern these phenomena are the Atwood number (measuring the original density contrast) and the Mach number. The experiments described here take place in a vertical shock tube with large, square internal cross section. The initial condition consists of a shear layer between helium and argon. A downward-propagating planar shock wave of Mach number 1.6 or 2.2 accelerates the interface. Measurements of 2-D concentration and velocity fields in a vertical cross section of the flow are obtained using planar laser-induced fluorescence (PLIF) and particle image velocimetry (PIV), respectively. Field statistics and integral quantities are extracted from these data and turbulence and mixing parameters are evaluated. From them, the outer scale Reynolds number is estimated to reach between 10,000 and 20,000 at the late times, indicating that the flow has crossed the threshold of fully developed turbulence.
The MegaJoule Direct Drive Campaign: NIF Experiments on the Pathway to MJ Yield
April 22, 2021

Michael Rosenberg
Laboratory for Laser Energetics – University of Rochester
Laser direct drive is one of three main approaches to achieving inertial confinement fusion ignition and high yield in the laboratory. While cryogenic direct-drive implosions designed to optimize implosion performance are conducted on the 30-kJ OMEGA laser, MJ-scale experiments on the National Ignition Facility (NIF) are critical to understand scale-dependent aspects of direct-drive physics – principally related to laser-plasma interactions – at ignition-relevant conditions. Spherical-geometry experiments over a range of convergence ratios have shown control of laser energy coupling and implosion symmetry using contoured shells and beam pointing, and wavelength detuning has been used to partially mitigate cross-beam energy transfer. Stimulated Raman scattering has been identified as a primary source of hot electrons and mid-Z layers have been found to reduce hot electron preheat in implosions. Planar and spherical experiments have generated x-ray radiography data to diagnose laser imprint and imprint mitigation using high-Z coatings. Low-convergence implosions are being explored as neutron sources, and a staged set of enhancements to NIF are proposed to allow for increased convergence and yield.
April 15, 2021

David Turnbull
Laboratory for Laser Energetics – Rochester
Plasma heating by inverse bremsstrahlung absorption of electromagnetic radiation was predicted to result in non-Maxwellian electron distribution functions (EDFs) more than 40 years ago, self-consistently modifying the absorption itself1 . Fokker-Planck simulations suggested that the bulk electrons in such EDFs should be close to super-Gaussian, with an exponent 2<m<5 that is a function of the overlapped laser intensity2. In such plasmas, ion-acoustic wave (IAW) frequencies were also shown to increase monotonically with the super-Gaussian exponent, with implications for IAW instabilities including crossed-beam energy transfer (CBET)3 . It was also theorized, however, that the tails of the EDF might deviate from the bulk distribution. Despite the many implications for laser-plasma experiments, these predictions remained largely untested for decades. I will discuss recent experiments at the University of Rochester Laboratory for Laser Energetics that have validated many of these predictions, including the shape of the laser-heated EDFs4 and their impacts on CBET5 and absorption.
Stochastic sampling of dense matter
April 8, 2021

Chris Pickard
University of Cambridge
High pressure and materials research has been transformed by the ability to predict both the structures and properties of materials from first principles. In many cases these predictions have been later confirmed by experiment. In others they have provided fruitful new directions to explore.
This progress has been achieved through the combination of stochastic approaches with reliable and efficient first principles methods. Diverse ensembles of initial structures can be generated, and structurally optimized. The resulting low energy structures are candidates for stable, and metastable, phases and/or defects and interfaces that might be experimentally realized. Success, of course, depends on a sufficiently broad and thorough sampling of configuration space.
A purely random strategy, as employed by Ab Initio Random Structure Searching (AIRSS),[1,2] is entirely parallel, and a natural fit to the high throughput computation (HTC) paradigm. Challenging cases can be tackled by designing the initial random structures so that they focus the search in regions of configuration space that are anticipated to yield success.
The design of these random “sensible” structures will be explored, along with some new directions [3] which promise to help our understanding of, and accelerate random search, along with applications to high pressure and materials research – from dense hydrides approaching room temperature superconductivity, to surprising astrophysical reactions and complex interfacial materials.
Laser-driven coils, how well do they work?
April 1, 2021

Jonathan Peebles
Laboratory for Laser Energetics – University of Rochester
Over the last decade, magnetic fields generated from a laser-driven current passing through a coil have become increasingly popular. The laser driven coil (LDC) fills a unique role in HED and potentially ICF science by providing magnetic fields to laser facilities without the need for bulky, destructive pulsed power devices, which are often incompatible with lasers due to debris. B-dot probes, Faraday rotation, and transverse (perpendicular to the coil axis) proton radiography have been used in previous LDC experiments, where fields of 1 kilo-Tesla over a millimeter cubed volume are commonly cited. However, in the body of recent work studying these coils, kilo-Tesla level fields are not the only measurements that have been made. Fields from LDCs vary over several orders of magnitude with different designs and drivers; in some cases, the same experiment has magnetic field measurements that differ by close to an order of magnitude depending on which diagnostic is being used.
To clarify the results of previous work, and to gain an understanding of which diagnostics are more reliable in this regime, we performed LDC experiments on OMEGA-EP using all of the aforementioned diagnostics, and have introduced a new technique called axial proton probing. The diagnostic responses for the experiment were compared with those for a known magnetic field. Not only was a consistent result found between the four primary diagnostics, but the results provided information on the diagnostics themselves, and some additional insight that may help explain the findings of other previous experiments.
SPARC and the high-field path to fusion energy
March 25, 2021

Martin Greenwald
MIT – Plasma Science & Fusion Center
The SPARC tokamak is currently under design as a mid-sized, deuterium-tritium (DT) burning magnetic confinement experiment. By employing novel high-temperature superconducting magnets, it will operate at 12.2 T in a device of a size and configuration similar to many experiments that have been deployed in the world’s fusion research program. Operation at high field will however, allow SPARC to be the world’s first experiment to create and confine a plasma that produces net fusion power. The performance to satisfy that mission has been defined as a fusion gain, Q > 2 and PFusion > 50 MW which would be comfortably more than the 25 MW of RF input power. Achieving this goal, we believe, would be a sufficient demonstration to place fusion firmly into the world’s energy plans. Significant margin against uncertainties in performance assumptions has been built into the design such that well-established physics predicts that SPARC could produce more than 140 MW of fusion power with Q > 10. Successful operation of SPARC would inform and enable the construction of a fusion pilot plant – a device with a major radius of about 3 m, producing over 500 MW of fusion power.
Materials microstructures in high pressure experiments
March 11, 2021

Sébastien Merkel
Université de Lille – CNRS
Microstructures define the arrangement of elements within a material, including phase distributions, grain sizes or grain orientations, and play a key role in defining materials properties. In the geosciences, microstructures affect the propagation of seismic wave and can be used to infer dynamic processes deep inside the Earth based on seismic observations. In materials science, microstructures affect the material’s mechanical properties, such, as strength. Phase transformations and plastic deformation can affect microstructures in a material and both effects can be studied under extreme conditions. In this seminar, I will show how new experiments can be used to study microstructures and the underlying physical mechanisms, both in static and dynamic experiments.
In the first part of the presentation, I will look at phase transformations in minerals. I will present the technique of multigrain crystallography in the diamond anvil cell and how it can be used for follow the distribution of phases, number of grains, and grain orientations in materials undergoing phase transformation and deformation, with applications in the field of geophysics. In the second part of the presentation, I will show how new designs of laser-driven compression experiments coupled with X-ray free electron lasers that can be used to study stress and texture in polycrystals at extreme strain rates. I will show how the technique can be used along with results on the hcp phase of Fe.
Cognitive Simulation: combining simulation and experiment with artificial intelligence
March 4, 2021

Brian Spears
Lawrence Livermore National Laboratory
Large-scale scientific endeavors often focus on improving predictive capabilities by challenging theory-driven simulations with experimental data. Yet, both simulation and experiment have become overwhelmingly rich, with a complex of observables including scalars, vector-valued data, and various images. At Lawrence Livermore National Laboratory (LLNL), we are using modern artificial intelligence (AI) technologies to combine predictive simulation models with rich experimental data. We call this set of methods cognitive simulation. We will describe a strategic LLNL research effort aimed at using recent advances in deep learning, computational workflows, and computer architectures to develop improved predictive models.
We will present work from a wide range of applications, including using inertial confinement fusion research and experiments at the world’s largest laser, the National Ignition Facility (NIF), as a testbed. We will describe advances in machine learning architectures and methods necessary to handle strong nonlinearities and multimodal data in ICF science and other applications. We will also cover state-of-the-art tools that we developed to steer physics simulation, uncertainty quantification, and model training at enormous scale. We finally describe our ongoing efforts to combine these technologies to support a broad spectrum of Lab science applications. We will especially emphasize development of self-driving, high-repetition-rate lasers as a prototype for embedding AI technologies in next-gen experimental facilities.
Overview and progress of materials experiments using the NIF ramp compression platform
February 25, 2021

Suzanne Ali
Lawrence Livermore National Laboratory
It is important to a number of fields to be able to accurately simulate processes and material responses under extreme conditions. Using sophisticated hydrodynamic codes, we can model giant impacts, planetary formation, and inertial confinement fusion implosions. The degree to which these simulations reflect reality, however, is dependent on how well we understand the materials and physics involved. Dynamic compression experiments are one of our vital tools for improving our understanding of material properties under extreme conditions, and I will be presenting on the development and status of the Ramp Compression Campaign on the National Ignition Facility. Obtaining high-precision, accurate ramp-compression data on materials under extreme conditions requires a well-validated platform. To date, we have addressed key issues in the development of ramp compression on the NIF: we have demonstrated the ability to ramp-compress metals to high pressure, including copper to ~23 TPa, we have developed analysis tools and experimental design predictive capability, and we have performed cross-platform equation of state (EOS) experiments validating the NIF platform.
Plasma acceleration and high energy density science
February 18, 2021

Cameron Geddes
BELLA Center – Lawrence Berkeley National Laboratory
Ultrashort pulse lasers enable resonant excitation of plasma waves, efficiently driving structures that can accelerate particles at rates of in the range of a GeV per centimeter. Guiding of such lasers in plasma structures formed by laser heating, capillary discharges and most recently by combining these two techniques has extended the depth of interaction from millimeter to tens of centimeter scale, enabling energies up to 7.8 GeV to be achieved. Experiments to combine two such stages at multi-GeV energies are being prepared. At the GeV energy scale, compact electron beams are being used to develop novel compact photon sources including free electron lasers, and MeV photons from Thomson scattering. The same laser pulses are being used for acceleration of ions from solid targets using target sheath fields, and experiments are being planned to access more efficient ion acceleration regimes and new frontiers in high energy density science in the near future, supported by a new short focal length capability. While these experiments are proving the building blocks of a future plasma based high energy physics collider and photon sources, laser development holds the key to scaling to the repetition rate and precision required.
Exploring the most Extreme Conditions of Matter with ultra-bright X-rays
February 11, 2021

Siegfriend Glenzer
SLAC – National Accelerator Laboratory
Standford University
Normally, what surrounds us are gases, liquids, or solids. But elsewhere in the universe, 99% of the observable matter exists under extreme conditions that lead to exotic states of matter and the formation of plasmas and warm dense matter. Specifically, near the center of Jupiter, hydrogen becomes liquid or even solid - a process important to understand the evolution of our solar system. In the center of the sun, hydrogen is a plasma that burns itself up by nuclear fusion - a process humans want to harness for clean energy production on earth. In the mantle of Neptune, hydrogen and carbon cannot mix and are postulated to form giant diamonds – a process that can explain Neptune’s excess heat generation. On the other hand, very hot plasmas are postulated to eject particles that we can observe as cosmic rays and that are a million times more energetic than mankind’s largest machines. At SLAC, we are now studying these extreme states of matter in the laboratory. We apply enormous pressures to earthbound samples and use our X-ray laser, the Linac Coherent Light Source, to take split-second photographs of the states that result. This lecture will describe these experiments. The information we are gathering provides fundamental insights into the physical properties of matter in extreme conditions whose understanding is important for modeling astrophysical processes and for pursuing controlled fusion. To further advance this field, a new upgrade has been proposed to bring state-of-the art lasers to the LCLX X-ray beam and which has recently been reviewed and endorsed by the US user community.
Solving the Many-Electron Schrödinger Equation with Deep Neural Networks
February 4, 2021

Matthew Foulkes
Imperial College London
Given access to accurate solutions of the many-electron Schrödinger equation, much of chemistry could be derived from first principles. Exact wavefunctions of interesting chemical systems are out of reach because they are NP-hard to compute in general, but approximations can be found using polynomially-scaling algorithms. The key challenge for many of these algorithms is the choice of approximate or "trial" wavefunction, which must balance efficiency versus accuracy. Neural networks have shown impressive power as accurate practical function approximators and promise as a compact trial wavefunctions for spin systems, but problems in electronic structure require wavefunctions obeying Fermi-Dirac statistics. Here we introduce a new deep learning architecture, the Fermionic Neural Network, as a powerful trial wavefunction for many-electron systems. FermiNet is able to achieve accuracy beyond other variational quantum Monte Carlo trial wavefunctions for a variety of atoms and molecules. Using no data other than atomic positions and charges, we predict the dissociation curves of the nitrogen molecule and hydrogen chain, two challenging strongly-correlated systems, to significantly higher accuracy than the coupled cluster method, widely considered the most precise scalable method for quantum chemistry at equilibrium geometry. This demonstrates that neural-network wavefunctions can improve the simple and appealing variational quantum Monte Carlo method to the point where it outperforms much more complex ab-initio quantum chemistry methods, opening the possibility of accurate direct optimization of wavefunctions for previously intractable molecules and solids.
An alternate approach to the ignition regime for inertial confinement fusion

January 28, 2021
Steve MacLaren
Lawrence Livermore National Laboratory
In inertial confinement fusion, the threshold for ignition is a highly dynamic quantity as the sources and sinks of power in the hot spot can vary rapidly. In this talk, we consider the ignition condition as a race between heating and disassembly rates and combine this ansatz with a prior solution to the fusion hot-spot thermodynamics to develop a Lawson-like ignition criteria for pressure X confinement time (p-tau) versus temperature. Low-Z capsule designs reach the temperature for this threshold using as much of the shell as feasible as ablator but then are limited in confinement time due to low stagnated mass. An alternate approach, the pushered single shell (PSS) introduces a dense inner layer of Mo-Be alloy that is smoothly graded outward to pure Be, increasing the confinement time at stagnation and lowering the temperature requirement at the ignition threshold. We describe both the design of and initial experimental results from this type of capsule.
Investigating the Physics of Burning Thermonuclear Plasmas
January 14, 2021

Brian Appelbe
Imperial College London
A burning thermonuclear plasma is a unique plasma environment. It is characterized by extremely large temperatures, densities and fluxes of α particles and radiation that evolve over very short temporal and spatial scales. A key question in ICF is how the transport processes accompanying these conditions affect the achievable yield. Furthermore, the effects of a magnetic field in a burning plasma deserve attention due to current research into magnetically-assisted ICF and Magneto-Inertial Fusion schemes, and the possible presence of self-generated magnetic fields in ICF experiments.
This talk summarizes results from a theoretical and computational investigation of burning plasmas, with and without magnetic fields, with a particular focus on two novel results. Firstly, it is shown that the interaction of a flux of α particles with a thermal plasma can induce an electronic current in the plasma. This current leads to new transport processes in burning plasmas. Secondly, the presence of a magnetic field in a propagating thermonuclear burn wave can lead to the formation of transport barrier at the burn front, reducing the rate of burn propagation.
Future Perspective for High-Intensity Laser HED Science
January 7, 2021

Tammy Ma
Lawrence Livermore National Laboratory
The Advanced Photon Technologies (APT) high-intensity HED science program at LLNL seeks to provide new capability in, and drive forward frontier HED with short-pulse laser science and applications. We will discuss recent work to develop laser-driven sources for DOE applications, including multi-ps, very high energy short pulse laser experiments on the NIF-ARC laser; and describe work towards a closed-loop paradigm to accelerate scientific discovery, integrating high-repetition-rate laser experiments, machine learning, and physics-based cognitive simulations. Using these novel tools, areas of active research include high-intensity laser interactions with matter, laser-driven secondary sources, plasma optics, future light sources, and the development of high-throughput diagnostics, targetry, modeling, and machine learning. Finally, we will touch on efforts to develop a purposeful set of partnerships and engagements to better leverage both national and international HED efforts.
Magnetic Signatures of Radiation-Driven Double Ablation Fronts
December 7, 2020

Louise Willingale
University of Michigan
Laser-plasma interactions produce strong temperature and density gradients that generate megagauss strength magnetic fields through the Biermann-battery effect. We performed experiments using the OMEGA EP laser system and used proton radiography to measure the strength, spatial profile, and temporal dynamics of the self-generated magnetic fields. The target material was varied and the plastic (CH), aluminum, copper, or gold targets exhibited different magnetic field structures. Mid-Z targets had two distinct regions of magnetic field, one produced by gradients from electron thermal transport and the second from radiation-driven gradients. Extended magnetohydrodynamic simulations including radiation transport reproduced the key experimental features, including the magnetic field generation and double ablation front formation.
Exploring the universe through Discovery Science on the National Ignition Facility (NIF)
December 3, 2020

Bruce Remington
Lawrence Livermore National Laboratory
Highlights from the NIF Discovery Science program will be presented. Examples include nuclear reactions relevant to stellar nucleosynthesis [1]; equations of state at high pressures relevant to planetary interiors [2, 3, 4] and white dwarf envelopes [5]; Rayleigh-Taylor instabilities relevant to supernovae and supernova remnant evolution [6, 7, 8]; relativistically hot plasmas [9] and target normal sheath acceleration of protons on NIF ARC [10]; magnetic reconnection at high energy densities [11]; and high velocity interpenetrating plasmas that generate collisionless astrophysical shocks, magnetic fields, and accelerate particles relevant to cosmic ray generation [12, 13].
Latest results from surveying the high-energy sky
November 19, 2020

Marcus Brüggen
Universität Hamburg
The new generation of radio interferometers, such as MeerKAT, ASKAP and LOFAR, as well as the recently launched X-ray observatory eROSITA provide a new view of the high-energy Universe.
They deliver new insights into a large range of astronomical phenomena, such as active galactic nuclei, cosmic rays and magnetic fields, galaxy clusters, the Warm-Hot Intergalactic Medium and Dark Energy.
In my talk I will present new results from on-going radio surveys and the first data from the Russian-German space observatory eROSITA. I will focus on my work on galaxy clusters and the filaments that connect them, cosmic magnetic fields and particle acceleration in cosmological structures.
Calculating Melting Curves for Crystallizing Stars
November 5, 2020

Simon Blouin
Los Alamos National Laboratory
White dwarfs are burned-out stars condemned to a slow cooling that extends over billions of years. Thanks to this simple evolution, it is relatively easy to measure their ages, making them useful cosmic clocks to study the history of our Galaxy. Eventually, the dense C/O plasma that makes up their cores becomes so correlated that it freezes. This process releases latent heat as well as gravitational energy due to the sedimentation of the O-enriched solid. This new energy source temporarily slows the cooling of the white dwarf and it is important to precisely model it if those stars are to be used as accurate cosmic clocks. Both the melting temperature and the importance of O sedimentation depend on the exact shape of the C/O phase diagram. To obtain an accurate version of this phase diagram, we have developed a new technique to compute the melting curves of multi-component plasmas. It is based on the Gibbs-Duhem integration technique and semi-grand canonical Monte-Carlo simulations of the liquid and solid phases of the screened, partially relativistic, fully ionized mixture. This approach is 200 times less costly than the competing technique where two-phase molecular dynamics simulations are used, thus allowing a finer sampling of the phase diagram and a vastly superior mitigation of finite-size effects. Our results lead to an improved match between white dwarf cooling models and astronomical observations, and highlight the role played by minor species in white dwarf evolution. This now well-tested method also presents an interesting potential for non-astrophysical systems (e.g., alloys).
October 29, 2020

Bingqing Cheng
University of Cambridge
A central goal of computational physics and chemistry is to predict material properties using first principles methods based on the fundamental laws of quantum mechanics. However, the high computational costs of these methods typically prevent rigorous predictions of quantities at finite temperatures, such as chemical potential, heat capacity and thermal conductivity.
In this talk, I will first discuss how to enable such predictions by combining advanced statistical mechanics with data-driven machine learning interatomic potentials. As an example [1], for the omnipresent and technologically essential system of water, a first-principles thermodynamic description not only leads to excellent agreement with experiments, but also reveals the crucial role of nuclear quantum fluctuations in modulating the thermodynamic stabilities of different phases of water. As another example [2], we simulated the high pressure hydrogen system with converged system size and simulation length, and found, contrary to established beliefs, supercritical behaviour of liquid hydrogen above the melting line.
Besides the computation of thermodynamic properties, I will talk about transport properties:
Ref [3] proposed a method to compute the heat conductivities of liquid just from equilibrium molecular dynamics trajectories.
During the second part of the talk, I will rationalize why machine learning potentials work at all, and in particular, the locality argument.
I'll show that a machine-learning potential trained on liquid water alone can predict the properties of diverse ice phases, because all the local environments characterising the ice phases are found in liquid water [4].
Adapting x-ray microcalorimeter spectrometers to diagnose magnetically confined plasma
October 22, 2020

Megan Eckart
Lawrence Livermore National Laboratory
X-ray microcalorimeter spectrometers have been developed for astrophysics space missions, providing imaging arrays with few-eV spectral resolution, but they also offer advantages for use on magnetic fusion energy devices. We recently deployed one of our LLNL/NASA x-ray microcalorimeter spectrometers to the Madison Symmetric Torus (MST) facility at the Wisconsin Plasma Physics Laboratory (WiPPL) and recorded x-ray photons emitted by the helium-like Al impurity ions in a majority deuterium plasma. In this talk we’ll introduce microcalorimeter detectors and discuss the diagnostic capability for magnetic fusion energy experiments, highlighting our experimental work toward demonstrating this capability at MST.
Microcalorimeter spectrometers combine the best characteristics of the x-ray instrumentation currently available on fusion devices: high spectral resolution similar to an x-ray crystal spectrometer, and the broadband coverage (from 0.1 keV to above 12 keV) of an x-ray pulse height analysis system. Fusion experiments are increasingly employing high-Z plasma-facing components, and require measurement of the concentration of all impurity ion species in the plasma. This diagnostic has the capability to satisfy this need for multi-species impurity ion data, and will also contribute to measurements of impurity ion temperature and flow velocity, Zeff, and electron density.
This work is funded by the DOE Office of Science, FES Measurement Innovation program. It is a collaboration between LLNL, WiPPL, and NASA Goddard Space Flight Center.
Coupling of Laser Angular Momentum to Plasma for the Generation of Kilo-Tesla Magnetic Fields
October 15, 2020

Andrew Longman
University of Alberta
Post Doc Fellow, HEDS Center
The generation and application of strong (kilo-Tesla) magnetic fields for the study of magnetized ICF, fast ignition, laboratory astrophysics, and particle acceleration/guiding is an area of great and growing interest. In this presentation, we will explore the novel approach for generating kilo-Tesla scale magnetic fields via the inverse Faraday effect driven by lasers carrying angular momentum.
The inverse Faraday effect describes the coupling of laser angular momentum directly to plasma electrons and has the unique advantage of not requiring a solid or structured target, making it suitable for both high repetition rate experiments, and in configurations where solid coils are not permissible.
We will numerically explore the inverse Faraday effect in under-dense plasmas with both circularly polarized (CP) beams, and with structured beams carrying orbital angular momentum (OAM). The simulations are carried out using full 3D PIC calculations with Titan-like laser parameters. We demonstrate kilo-Tesla fields extending more than 100 microns in length, and with decay times on the order of picoseconds when driven by 100 femtosecond pulses. We will discuss the advantages and disadvantages of this approach, as well as discussing possible experimental configurations to demonstrate and measure the fields.
The High Energy Density Science Center: 2020 year in review
October 8, 2020

Frank Graziani
Lawrence Livermore National Laboratory
The High Energy Density Science Center (HEDSC) was established in late 2015 through a joint agreement between the Physical and Life Sciences, Weapons and Complex Integration, and NIF and Photon Science directorates. The Center’s goal is to build a high energy density community through support of, and collaboration with, academic partners and to integrate those efforts with the programs at LLNL. The Center is built around four focus areas: (1) education, (2) outreach through workshops and seminars, (3) workforce pipeline to the programs, and (4) enabling research collaborations between LLNL and academic partners. In this talk, we will present the year 2020 in review and look at what lies ahead in 2021. The year 2020 was a year of both growth and challenges. 2020 saw growth in education programs with a quarter long course on HED diagnostics offered in collaboration with UCSD in addition to the selection of a new HEDS Center postdoctoral fellow. Besides educating the next generation of HED scientists, the HEDS Center continues training students through internships and thesis opportunities. Our outreach and collaboration activities continue through a vibrant seminar series, university partnerships, a planned sabbatical program and visits to community colleges and undergraduate institutions. Inclusion and diversity is an important aspect of our mission and the Consortium for HEDS (FAMU, UC Merced, Morehouse and LLNL) received new funding from NNSA. The Consortium’s goal is to provide research and education opportunities in HEDS for under-represented groups and thereby increase diversity in the field. With the arrival of COVID and working off-site, the HEDS Center had to react to the change. The summer internship program continued, on-line. The sabbatical program and visits to community and undergraduate colleges was put on hold and instead, the Center decided to produce a series of HEDS educational videos for the public. In 2021 we hope to bring back the sabbatical program and outreach visits to K-12 and community and undergraduate colleges. A call for a new HEDS Fellow postdoc position is out and more HED education programs are planned. In 2021 we will continue to foster international collaboration in HEDS, bring on another thesis student from FAMU and continue the internship program.
MeV X-ray Radiography on High Intensity Lasers using Compound Parabolic Concentrators
September 10, 2020

Dean Rusby
Lawrence Livermore National Laboratory
High Intensity laser interactions produce a high current beam of electrons that can be used for many applications. One such applications is the production of a high energy and bright x-ray source via bremsstrahlung. These x-rays possess several qualities, such as pulse durations and high spatial resolutions, that make them ideal for radiography applications. The key to making the brightest x-ray source is converting as much energy as possible from the laser into high energy electrons, which often requires the highest intensity lasers. We have developed an alternative method using a novel target design, the compound parabolic concentrator (CPC) that can be used to confine, focus and couple more laser energy into the electrons. Experimental measurements have been performed that demonstrate the capabilities of CPCs targets and show that they can produce electrons and x-rays that far outperform planar targets. We also demonstrate the enhancement in x-ray radiography in the MeV regime.
August 27, 2020
Joyce Guzik
Los Alamos National Laboratory
In 2004, improved analyses of solar spectra resulted in a downward revision of the abundances of elements heavier than hydrogen and helium, in particular, the elements C, N, and O. Solar models evolved using these lower abundances showed discrepancies with inferences from solar oscillation observations (helioseismology). This problem has not been solved satisfactorily in the intervening 16 years. How serious/important is this problem?
This talk will give an overview of how standard solar models are calculated and of the constraints from helioseismology. The talk will also present results of some attempts to change input physics or assumptions in the standard solar model, including opacity modifications, to try to resolve the discrepancies. I would like to have a discussion with the participants after the talk about which directions appear most promising to resolve the problem.
The response of solids to irradiation by massive particles
August 20, 2020

Michael Demkowicz
Department of Materials Science and Engineering, Texas A&M University
Solids are subjected to bombardment by high-energy, massive particles (electrons, neutrons, ions) in a wide range of energy, weapons, and astrophysical scenarios. I will summarize the fundamental mechanisms by which solids—especially metals—respond to such irradiation, from the dissipation of the particle’s energy in the course of a collision cascade to the generation and subsequent evolution of damage in the material. I will then present a selection of recent research on radiation response—carried out primarily using molecular dynamics simulations—focusing on amorphous and nanocomposite metals. I will conclude with a discussion of prospects for developing novel, radiation-resistant materials based on insights gained from this research.
Speed-Limited Particle In Cell and Getting to the Answer Faster
August 6, 2020

John Cary
University of Colorado
Tech X
Speed-limited particle-in-cell (SLPIC) is an algorithm for achieving orders of magnitude speedup of simulations in cases where kinetic electron effects are important, yet the motion is slow compared with the electron thermal velocity. This is the case for nearly all low-frequency plasma dynamics, but it is especially so for low-temperature plasma discharges where (1) the ions are cold compared with the electrons and (2) the ions are comparatively even more massive, e.g., in Argon discharges. This method has several quirks, including the need to have both a charge and a current weight. This method has now been generalized to include collisions and secondary emission, thereby allowing it to be applied to determine the Paschen curve in irregular geometries. The theory of this new algorithm will be presented along with results. In addition, there will be a few remarks on other subjects, such as device computing and user-friendly code, that contribute to reducing time to solution.
July 30, 2020

Katie Lewis
Lawrence Livermore National Laboratory
Scientific simulations have driven computing at Lawrence Livermore National Laboratory (LLNL) for decades. During that time, we have seen significant changes in hardware, tools, and algorithms. Today, data science, including machine learning, is one of the fastest growing areas of computing, and LLNL is investing in hardware, applications, and algorithms in this space. While the use of simulations to focus and understand experiments is well accepted in our community, machine learning brings new challenges that need to be addressed. I will explore applications for machine learning in scientific simulations that are showing promising results and further investigation that is needed to better understand its usefulness.
July 9, 2020

Mike Campbell
Laboratory for Laser Energetics, University of Rochester
The Richtmyer-Meshkov instability (RMI) develops upon impulsive acceleration of the interface between fluids of different acoustic impedance. The RMI consists in the unbounded growth of any perturbations initially present on the interface, and it is a consequence of the baroclinical deposition of vorticity on the interface. Eventually, the interface develops into a turbulent layer leading to the mixing of the two fluids. Flows of this type occur in nature and in man-made settings, over very large ranges of length, time, and energy scales: from experiments for the attainment of inertial confinement fusion (ICF), to supersonic combustion systems, to supernovae explosions. Shock-induced mixing has very negative effects in the case of ICF while it holds great potential to improve the combustion processes in the case of hypersonic engines. Two of the fundamental parameters that govern these phenomena are the Atwood number (measuring the original density contrast) and the Mach number. The experiments described here take place in a vertical shock tube with large, square internal cross section. The initial condition consists of a shear layer between helium and argon. A downward-propagating planar shock wave of Mach number 1.6 or 2.2 accelerates the interface. Measurements of 2-D concentration and velocity fields in a vertical cross section of the flow are obtained using planar laser-induced fluorescence (PLIF) and particle image velocimetry (PIV), respectively. Field statistics and integral quantities are extracted from these data and turbulence and mixing parameters are evaluated. From them, the outer scale Reynolds number is estimated to reach between 10,000 and 20,000 at the late times, indicating that the flow has crossed the threshold of fully developed turbulence.
Nuclear Science Experiments for National Security and Fundamental Science on NIF
July 2, 2020

Dawn Shaughnessy
Lawrence Livermore National Laboratory
The National Ignition Facility (NIF) is the world’s largest laser and is a major contributor to the Stockpile Stewardship Program conducting state of the art science in high energy density physics including fusion research. Developing the mission, science, technology, and support for projects of the scale of NIF is a demanding and multifaceted enterprise. There are many lessons to be learned from the NIF experience that can be applied in the quest to secure any future large-scale facility. This presentation will include a historical perspective on inertial confinement fusion (ICF) at Lawrence Livermore National Laboratory and the Stockpile Stewardship Program that motivated the NIF and the scientific and political strategy that ultimately secured the Facility.
Graph theory ideas reveal long range conduction pathways
June 11, 2020

Maria Gomez
Department of Chemistry, Mount Holyoke College
Finding long range conduction pathways is challenging when the system includes both fast frequency modes needing short time step force integration and slow frequency modes requiring long time samples. Methods such as kinetic Monte Carlo (kMC) avoid the integration of steps and instead use probabilities to choose the next moves and advanced the clock based on the move chosen. Nevertheless, extracting fast conduction mechanisms between traps can be challenging. Centrality methods based on the number of steps to return to key sites or vertices in a graph have been used to identify the most central areas in a graph. However, physical systems with traps and highways have steps with distinctly different barriers making steps non-equivalent. This seminar reviews both traditional and new graph theory schemes for finding long range pathways with a special focus on a centrality measure that instead of using the number of steps to return to sites considers the time of first returns [1] and its applications to proton conduction in doped perovskites[2]. In these systems shown below a single image including all proton binding sites with the most central sites shown in darker shades of grey shows both trapped regions and fast conduction highways.
Jupiter Revealed
June 4, 2020

Marius Millot
Lawrence Livermore National Laboratory
We will stream the documentary movie Jupiter Revealed from the BBC's Horizon show. This film describes new discoveries about the planet Jupiter following the success of the NASA Juno probe mission and how these discoveries help us better understand how planet form and evolve. One of the segments was filmed at the National Ignition Facility in Livermore. This segment highlights a series of Discovery Science experiments conducted at NIF to explore the exotic properties of metallic Hydrogen.
Laser-Plasma Accelerators: Riding the Wave to the Next Generation X-Ray Light Sources
May 14, 2020

Félicie Albert
Lawrence Livermore National Laboratory
Particle accelerators have been revolutionizing discoveries in science, medicine, industry and national security for more than a century. An estimated 30,000 particle accelerators are active around the world. In these machines, electromagnetic fields accelerate charged particles, such as electrons, protons, ions or positrons to velocities nearing the speed of light. Although their scientific appeal will remain evident for many decades, one limitation of the current generation of particle accelerators is their tremendous size (typically a mile long) and cost, which often limits access to the broader scientific community. A plasma is a neutral medium composed of negatively charged free electrons and positively charged ions. Plasma can sustain electrical fields three orders of magnitude higher than that of conventional particle accelerators. Acceleration of electrons in laser-driven plasmas has been drawing considerable attention over the past decade. These laser wakefield accelerators promise to dramatically reduce the size of accelerators and revolutionize applications in medicine, industry and basic sciences.
Harnessing Fusion: Building a Star on Earth
May 7, 2020

Tammy Ma
Lawrence Livermore National Laboratory
The National Ignition Facility (NIF) at the Lawrence Livermore National Laboratory (LLNL) is the world’s largest and most energetic laser system. The NIF is built to create very extreme states of matter – similar to those found in the interiors of stars and planets. Here, scientists and engineers are working hard to demonstrate sustainable fusion burn – the same reaction that occurs in the sun – to one day harness as a source of limitless, clean energy.
Towards Enabling Predictive Scale-Bridging Simulations through Active Learning
April 16, 2020

Jeffrey Haack
Los Alamos National Laboratory
Designing effective methods for multiscale simulation is a longstanding challenge. Our goal is to advance the state of the art for Machine Learning (ML) beyond sequential training and inference and facilitate scale bridging through novel techniques. Active Learning (AL) is a special case of semi-supervised ML in which a learning algorithm is able to interactively use the fine-scale model to obtain the desired outputs at new data points, making it ideal for concurrent scale-bridging. Our AL procedure will dynamically assess uncertainties of the ML model, query new fine scale simulations as necessary, and use the new data to incrementally improve our ML models. This capability will be demonstrated on two applications: transport in nanoporous media (e.g., for hydraulic fracturing) and inertial confinement fusion (ICF), validating against experimental data. Although the physics is quite dissimilar, both applications represent problems that suffer from inaccurate macro-scale predictions due to subscale physics that are ignored.
Laboratory equation of state measurements of the carbon envelopes of white dwarf stars
March 26, 2020

Andrea Kritcher
Lawrence Livermore National Laboratory
White dwarfs (WD) represent the final state of evolution for the vast majority of stars 1–3 . Certain classes of white dwarfs pulsate4, 5 , leading to observable brightness variations whose analysis with theoretical stellar models uniquely probes their internal structure. Modeling of these pulsating WD stars provides stringent tests of white dwarf models and a detailed picture of the outcome of the late stages of stellar evolution 6. However, these high energy den- sity states are extremely difficult to access and diagnose in the labo- ratory and as a result theory is largely untested at these conditions. Here, we present equation of state (EOS) measurements of matter at pressures ranging from 100-450 million atmospheres, where the understanding of WD stars is sensitive to the EOS and where mod- els show significant differences. We measure the pressure-density relationship along the principal shock Hugoniot of hydrocarbon to within five percent. The observed maximum compressibility is consistent with theoretical models that include detailed electronic structure, are used in calculations of WD stars and inertial con- finement fusion (ICF) experiments7, 8 , and predict an increase in compressibility due to ionization of the inner core orbitals of car- bon. We also find that detailed treatment of the electronic structure and the electron degeneracy pressure are required to capture the measured shape of the pressure-density evolution for hydrocarbon before peak compression.
Modern tests of vacuum-polarization effects in strong laser fields
March 5, 2020

Antonino Di Piazza
Max Planck Institute for Nuclear Physics
Quantum electrodynamics (QED) is a well-established physical theory, and its predictions have been confirmed experimentally in various regimes and with extremely high accuracy. However, there are still areas of QED that deserve theoretical and experimental investigation-- especially when physical processes occur in the presence of intense background electromagnetic fields, i.e., of the order of the so-called “critical” field of QED [1]. In the presence of electromagnetic fields of such high strength, for example, even the vacuum becomes unstable and electron-positron pair production spontaneously occurs.
After a broad introduction on strong-field QED, the seminar will describe different regimes of this theory and introduce present and upcoming experimental efforts to test it under such extreme conditions. As a prominent theoretical example of open problems, the talk will focus on how the properties of the vacuum are altered by intense background electromagnetic fields [1,2]. Unlike classical electrodynamics, QED predicts that electromagnetic fields also interact in vacuum through virtual electron-positron pairs. This is the physical origin of a number of so-called vacuum-polarization effects, which will be reviewed. Finally, the talk will discuss recent experimental suggestions to observe these effects by means of intense laser beams [3].
Theoretical foundations of quantum hydrodynamics for dense plasmas
February 27, 2020
Zhandos Moldabekov
Al Farabi Kazakh National University
Institute of Experimental and Theoretical Physics
Methods for large-scale simulation of time-dependent features of quantum plasmas are crucial for fundamental and applied problems. The microscopic theory of quantum hydrodynamics (MQHD), which goes beyond the random phase approximation by employing ab initio data for dynamic local field corrections, will be presented [1,2]. Quantum hydrodynamic theory is presented as the orbital averaging of the MQHD equations. The range of applicability of QHD is analyzed. Going beyond the gradient expansion approximation, a fully non-local Bohm potential is derived [1,2].
The results for the dynamic structure factor of ions at dense plasma and warm dense matter (WDM) conditions will also be presented [3,4]. The applicability of the classical generalized hydrodynamics and of the QHD for the description of collective oscillations of ions will be discussed. Additionally, the results for the energy loss characteristics of electrons at WDM and dense plasma conditions, where the static local field correction from ab initio QMC simulations [5] was used, will be presented. Finally, the first results for the friction coefficient acting upon ions due to electrons will be reported, where friction represents a correction to the Born-Oppenheimer approximation within Langevin dynamics simulation of ions.
The Efficacy of Simple Models for Non-Ideal Plasmas
February 6, 2020

Liam Stanton
Department of Mathematics and Statistics, San Jose State University
Computational models are formulated in hierarchies of variable fidelity, often with no quantitative rule for defining the fidelity boundaries. This talk will explore the extent to which simple screening models for ionic interactions can capture both the equilibrium structure and transport processes of non-ideal plasmas, such as dense plasmas found in inertial confinement fusion (ICF) experiments and ultra-cold neutral plasmas (UNPs). We have developed a simplified effective potential approach within a Boltzmann-type framework that yields accurate and computationally efficient fits for all of the relevant cross-sections and collision integrals needed to construct transport coefficients. Our results, which span the UNP-to-ICF regimes, have been validated with molecular dynamics (MD) simulations for self-diffusion, inter-diffusion, viscosity, thermal conductivity, and stopping power with promising comparisons to UNP experiments as well. MD simulations have also been used to examine the underlying assumptions of this effective Boltzmann approach through a categorization of behaviors of the velocity autocorrelation function. In addition, we have constructed a dataset from a wide range of atomistic computational models to reveal the accuracy boundary between these higher-fidelity models and simpler screening models based on finite-temperature orbital-free density functional theory. The symbolic decision boundary is discovered by optimizing a support vector machine on the data through iterative feature engineering. This machine-learning approach reveals a symbolic rule that is independent of the computational method and directly reveals the central role of atomic physics in determining accuracy.
Generalized Lawson Criteria for Inertial Confinement Fusion
January 23, 2020
Robert Tipton
Computation Physicist, Lawrence Livermore National Laboratory
In 1955 John Lawson proposed a criterion of ignition in the context of magnetic fusion. Over the decades, Lawson’s original criterion has been generalized in several different ways for the case of Inertial Confinement Fusion (ICF). This talk will describe the different generalizations and demonstrate their effectiveness with numerical simulations. The simulations indicate our best shots on NIF have a generalized Lawson criterion which is about 80% of the expected ignition value.
Spin crossover in iron in lower mantle minerals
January 16, 2020

Renata Wentzcovitch
Department of Applied Physics and Applied Mathematics and
Department of Earth and Environmental Science, Lamont Doherty Earth Observatory, Columbia University
Pressure and temperature induced spin-state change in iron in lower mantle minerals is an unusual phenomenon with previously unknown consequences. High pressure and high temperature experiments have offered a wealth of new information about this class of materials problems, which includes the insulator to metal transition in Mott systems. I will discuss key experimental data, contrast them with our ab initio results and thermodynamic models, show the implications for fundamental phenomena taking place at the atomic scale and their macroscopic manifestations, and discuss potential geophysical consequences of this phenomenon.
Simulating electronic structure under ultrafast compression with DFT and TDDFT
January 9, 2020

David Strubbe
Department of Physics, University of California, Merced
Many electronic-structure studies of warm dense matter have focused on the end-point of compression, in total thermal equilibrium, or perhaps a partial equilibrium with different electronic and lattice temperatures. In compression experiments at laser facilities such as NIF, the shock speed can reach 10 km/s, which is equivalent to 10 Å/fs. This means that a direct calculation of the compression process itself is actually feasible with first-principles methods because the compression operates on the natural length and time scales of these methods, such as time-dependent density-functional theory (TDDFT). The seminar will discuss progress toward TDDFT simulations of ultrafast compression processes, assessing numerical and conceptual issues of electronic dynamics with a rapidly varying unit cell. It will also present results on changes in band structure and optical absorption spectra of diamond structure silicon under extreme pressure but low temperature, in which transitions take place from semiconductor to semimetal to metal on short timescales before the structure can change to the other phases of silicon favored at high pressure. Finally, the seminar will cover our work on non-additive kinetic energy functionals, which can provide a route to improved DFT-based average-atom or neutral pseudo-atom models for high energy density science. This work is being carried out as part of the Consortium for High Energy Density Science.
Thermonuclear reactions probed at stellar core conditions with laser-based inertial confinement fusion
November 14, 2019
Daniel Casey
Lawrence Livermore National Laboratory
Laser-based inertial confinement fusion (ICF) implosions provide a path to study reactions in thermonuclear plasmas. However, ICF experiments have significant challenges not found in accelerator experiments. This talk explored how these issues can be overcome and ICF implosions can be used to make nuclear measurements in some specific circumstances. In particular, the method of yield ratios is used to infer astrophysical S-factors for two reactions using a third as a reference. The resulting data show excellent agreement with evaluations and prior accelerator data for these two reactions, bolstering confidence in this method. This technique is now being explored as a candidate for a future plasma-electron-screening experiment to attempt to observe enhancements to reaction rates in the presence of plasma electrons.
Astro-glaciology and habitability of planetary abysses: Experimental exploration of the richness of aqueous systems thermodynamics at high pressures
November 7, 2019
Baptiste Journaux
University of Washington
The presenter discussed his work related to studying the habitability of planetary interiors. The research team operated diamond anvil cell X-Ray diffraction experiments coupled with new advanced thermodynamic representation that allow scientists to accurately reproduce experimental data. This modular framework, based on local basis functions parameterization of a thermodynamic potential, allows accurate prediction of phase stability and realistic equilibrium thermodynamics in stable and metastable regime, and can be used in the representation of UHP experimental results.
Determination of the ion temperature in high-energy-density plasmas using the Stark Effect and Zeeman Effect induced by intense laser light
November 4, 2019
Yitzhak Maron
Weizmann Institute of Science, Israel
The presenter discussed an experimental method to determine the ion temperature based on the effect of ion coupling on the Stark line shapes. It was implemented on a Z-pinch stagnation, confirming that the ion thermal energy is small compared to the imploding-plasma kinetic energy, where most of the latter is converted to hydromotion. The seminar also included a discussion of the Zeeman Effect induced by intense laser light, with the presenter describing an analysis of spectral line shapes of hydrogen-like species subjected to fields of electromagnetic waves showing that the magnetic component of an electromagnetic wave may significantly influence the spectra. In particular, the Zeeman Effect induced by powerful visible or infrared lasers can be experimentally observed.
Material property measurements and theory into stellar regimes
October 31, 2019
Damian Swift
Lawrence Livermore National Laboratory
In real-world situations such as in stars, the behavior of matter at extreme conditions can be very sensitive to variations between widely used equation of state (EOS) models The presenter discussed work done by his team to develop experimental platforms accessing the EOS and atomic physics of matter in stellar regimes. Shock states up to ~80 TPa can be deduced from spherically converging shocks at LLNL’s National Ignition Facility, and the team recently improved the analysis to reduce uncertainties and infer off-Hugoniot data.
Perspectives on research in computational plasma physics with applications to experiments
October 17, 2019
Bruce Cohen
Lawrence Livermore National Laboratory
The presenter discussed his perspective on the development and application of computational plasma physics to plasmas in nature and in the laboratory. The examples described illustrated both fundamental plasma phenomena and the behavior of laboratory plasmas. Some of the specific examples included simulations of micro-instabilities in magnetic mirror, tokamak, and spheromak plasmas; laser-plasma interactions; and Knudsen-layer phenomena as it affects fusion performance. The examples also illustrated the development of models and algorithms that are well suited to simulating the phenomena of interest.
The many faces of matter inside neutron stars
October 10, 2019
Fridolin Weber
San Diego State University and
University of California, San Diego
In this talk, the presenter provided an overview of our current understanding of the composition of neutron stars. Models for the equation of state of dense neutron star matter were also presented, which are constrained by the latest nuclear and astrophysical data. Particular emphasis was put on quark de-confinement in the core regions of neutron stars. Finally, the phase diagram of hot and dense proto-neutron star matter was discussed, and possible instabilities in such matter were pointed out.
The High Energy Density Science Center: A year in review
October 3, 2019
Frank Graziani
Lawrence Livermore National Laboratory
In this talk, the director of LLNL’s HED Science Center presented the 2019 year in review and looked at what lies ahead in 2020. In 2019, the Center saw growth in its education programs, selected a deputy director, established a new HEDS Center postdoctoral fellowship, participated in LLNL’s Ambassador program, established closer ties with Japan’s HED efforts, delivered a vibrant seminar series, hosted summer student and thesis programs, and engaged in collaborations with many academic partners, including several minority serving institutions. The presenter also discussed plans for 2020, including a consortium of universities engaged in HED science education, selection of the HEDS Center postdoctoral fellow, hosting sabbatical programs, and various outreach programs.
Continuum dynamics and reactions in light nuclei
September 19, 2019
Sofia Quaglioni
Lawrence Livermore National Laboratory
An overarching goal of nuclear physics is to arrive at the comprehensive understanding—in terms of the laws of quantum mechanics and the underlying theory of the strong force (quantum chromodynamics)—of atomic nuclei and their interactions, and to use this understanding to accurately predict nuclear properties that play a fundamental role in explaining the inner workings of the Universe or are critical to national security. The presenter discussed first-principles calculations of nuclear structural and reaction properties to predict thermonuclear reaction rates of interest for fusion energy technology and stellar nucleosynthesis.
Overview of laser-produced relativistic electron-positron pairs
September 12, 2019
Hui Chen
Lawrence Livermore National Laboratory
Intense lasers are now the brightest source of relativistic electron-positron pair jets in the laboratory—up to 1012 of highly relativistic pairs are routinely produced in experiments at LLNL and other high power, short pulse lasers with energies from 100-2000 J. This talk reviewed experimental results to date. In addition, the presenter discussed the near-future in this research area, exploiting laser-produced pair jets for fundamental plasma physics studies, for diagnosing high-energy-density physics, and for laboratory experiments mimicking the physics processes in various astrophysical observations including Gamma Ray Bursts.
The exotic properties and structure of superionic water ice at Uranus and Neptune interior conditions
August 29, 2019
Federica Coppari
Lawrence Livermore National Laboratory
Since Bridgman’s discovery of five ice phases in 1912, studies on the extraordinary polymorphism of H2O have documented 17 crystalline and several amorphous structures, as well as metastability and kinetic effects. Particularly intriguing is the prediction that water becomes superionic—with liquid-like hydrogens diffusing through the solid lattice of oxygen—when subjected to extreme pressures exceeding 100 GPa and temperatures above 2,000 K. Optical measurements along the Hugoniot curve of ice VII showed evidence of superionic conduction but did not confirm the microscopic structure of superionic ice. The presenter discussed recent experiments at the OMEGA Laser that used shockwaves to simultaneously compress and heat liquid water samples to 100–400 GPa and 2,000–3,000 K. In-situ x-ray diffraction shows that under these conditions, water solidifies within a few nanoseconds into nanometer-sized ice grains that exhibit unambiguous evidence for the crystalline oxygen lattice of superionic water ice. These data allow us to document a temperature- and pressure-induced phase transformation from a body-centered-cubic ice phase to a novel face-centered-cubic, superionic ice phase.
Recombination in line broadening
August 15, 2019
Thomas Gomez
Sandia National Laboratories
Broadening of atomic lines is caused by a time-dependent perturbation on the atom due to the plasma ions and electrons surrounding it. The relative importance of each broadening mechanism depends on transitions and conditions. The broadening due to slow-moving ions is well understood compared with the broadening from electrons due to more complex time-dependent quantum-mechanical interaction with the radiating atom. In fact, there is a long-standing discrepancy between modeled and measured line width for these Li-like ions; this is known as the isolated-line problem. The presenter discussed common approximations and limitations in electron-broadening calculations, as well as the impact of our recent investigations on the isolated-line problem.
Nuclear astrophysics experiments at heavy-ion storage rings
August 1, 2019
Yuri Litvinov
GSI Helmholtzzentrum für Schwerionenforschung, Germany
Storage of freshly produced radioactive particles in a storage ring enables efficient use of the same rare ion multiple times. Employing heavy-ion storage rings for precision physics experiments with highly-charged ions (HCI) is a rapidly developing field of research. At the heavy-ion storage ring ESR at GSI, construction of dedicated heavy-ion storage rings have enhanced experimental capabilities by enabling stored and cooled secondary HCIs in the previously inaccessible low-energy range. The presenter highlighted research programs at heavy-ion storage rings, including physics experiments at the intersection of atomic, nuclear and possibly plasma physics.
Deep learning for non-local thermodynamic equilibrium in hydrocodes
July 25, 2019
Gilles Kluth
French Alternative Energies and Atomic Energy Commission, France
Commissariat à l'énergie atomique et aux énergies alternatives (CEA)
The presenter discussed the team’s work developing new techniques to accelerate radiation hydrodynamics simulations. The ultimate goal is to develop a fast representation of detailed atomic physics packages to give absorption coefficients, emissivities, and ionization states. The fast representation—in this case a deep neural network—can be called in place of a traditional physics package. The neural network is dramatically faster and uses substantially less memory. The team examined the NLTE physics of mid-Z materials for ICF simulations as a test application. They used Cretin for in-line collisional-radiative computations in the rad-hydrocode HYDRA, and they trained a deep neural network on a set of Cretin data under a broad set of plasma conditions. Finally, they replaced the in-line atomic physics computation in HYDRA with the well-trained neural network accelerator.
July 18, 2019
Thomas Schenkel
Lawrence Berkeley National Laboratory
The presenter discussed recent experiments at the BELLA petawatt laser that expanded its focus on electron acceleration to also include ion acceleration and laser-matter interactions with solid targets. The 1-Hz repetition rate of BELLA allows parametric explorations with thousands of shots. One example is nuclear reactions in plasmas and moderately hot targets, where unreasonably high values of apparent electron screening potentials have been observed in studies of light ion fusion that now can be investigated with higher precision. Pulsed ion beams provide access to the time domain of ion–solid interactions, and they have been used to drive materials very far from equilibrium. The talk reported on studies of color center qubit formation and damage accumulation in semiconductor devices with intense, pulsed ion beams.
Experimental observation of ion acoustic waves in warm dense methane
June 27, 2019
Thomas White
University of Nevada, Reno
The study of warm dense matter (WDM) has important applications, such as understanding controlled thermonuclear fusion and in material processing. Laboratory experiments are now able to create WDM states with a range of techniques, allowing critical tests of theory and modelling. Still, the experimental possibilities to diagnose dense matter are rather limited. Recent advances in free-electron laser technology have produced X-rays with a high enough flux in a small enough bandwidth to allow the properties of WDM to be probed on a shot-by-shot basis. The presenter provided an overview of X-ray scattering experiments, along with preliminary results of an experiment principally designed to measure the ion-ion dynamic structure factor and sound speed in warm dense methane. Some of these results were also compared to results from quantum and classical atomistic simulations.
Ion friction in strongly coupled plasmas
June 13, 2019
Scott Bergeson
Brigham Young University
The presenter discussed his research aimed at understanding ion-ion interactions in a multi-species, strongly coupled environment. Ion mass provides spatial confinement in high-density, laser-driven implosions of solid ices. Careful modeling of the target, as well as the laser profile and precision cryogenic targetry, are required to create targets of the right size, shape, structure, and density to optimize fusion yield. These efforts attempt to balance the competing demands of temperature, density, and size requirements for achieving self-sustained nuclear burn. Inertial confinement occurs as a competition between the ion response to the field generated by the other charges in the plasma (expansion) and the friction forces generated as distributions of ions move past each other (confinement). The presenter’s research team designed experiments to examine aspects of this confinement using a high-energy-density-plasma simulator.
Frontiers of high-pressure research at the European Synchrotron Radiation Facility
June 6, 2019
Sakura Pascarelli
European Synchrotron Radiation Facility (ESRF)
The presenter provided an overview of static and dynamic compression activities and recent scientific results obtained at the ESRF. She also discussed future projects and the unique science opportunities offered by ESRF’s Extremely Brilliant Source (EBS), which will be operational in 2020. The EBS will offer significantly higher flux density and higher coherence, leading to important perspectives for extreme matter studies. She described three EBS-related projects: (1) a high-flux, nano-X-ray, diffraction beamline for science at extreme conditions; (2) pushing the limits of nuclear resonant scattering in energy and spatial resolution; and (3) a high brilliance EXAFS beamline optimized for time resolved and extreme conditions applications.
Implications of Bell’s Theorem: What physicists get wrong
May 23, 2019
Kenneth Wharton
San Jose State University
Despite the fact that Bell’s Theorem tells us something profound about our universe, too many physicists dismiss it as a reconfirmation of something we already knew. Many others have a misapprehension of the main result, incorrectly believing that it rules out hidden variables or does not apply to probabilistic models. And even experts in quantum foundations are sometimes unaware of subtleties concerning the role of an “arrow of time” in Bell’s analysis, and an associated time-symmetric option for modeling entanglement phenomena in spacetime. This talk attempted to clarify these and other issues, surveying Bell’s Theorem and its fascinating implications.
Ab initio thermodynamic and dynamics results for the warm dense electron gas
May 16, 2019
Michael Bonitz
Kiel University, Germany
The presenter discussed his team’s work regarding warm dense matter (WDM), including obtaining ab initio thermodynamic results for the electron component in WDM based on novel quantum Monte Carlo (QMC) simulations. Based on these results, the first ab initio parametrization of the exchange-correlation free energy F_xc has been presented, which is a key input for DFT simulations of WDM.
May 9, 2019
Félicie Albert
Lawrence Livermore National Laboratory
The presenter discussed particle acceleration in laser-driven plasmas as an alternative to generating x-rays via high brightness x-ray sources, such as synchrotrons and x-ray free electron lasers (XFELs). When short, intense laser pulses are focused into a gas, it produces electron plasma waves in which electrons can be trapped and accelerated, a process known as laser-wakefield acceleration (LWFA). Betatron x-ray radiation, driven by electrons from LWFA, has unique properties that are analogous to synchrotron radiation, with a 1000-fold shorter pulse. This source is produced when relativistic electrons oscillate during the LWFA process. This approach to generating x-rays via laser-plasma acceleration offers the potential to overcome some of the drawbacks of using synchrotrons and XFELs, including their size and cost.
Understanding strongly correlated matter with experiments and simulations
May 2, 2019
Gianluca Gregori
University of Oxford, United Kingdom
Combining experiments at Free Electron Laser Facilities with state-of-art numerical simulations provide ways to further our understanding of warm dense matter. Perhaps the most successful and ubiquitous of these approaches has been the validation of density functional theory (DFT) against experimental data. However, despite the progress made by DFT and related schemes, there remain many problems that are intractable for existing methods, particularly if the full particle dynamics is needed. The presenter discussed how alternative approaches, based on the Bohmian trajectories formalism, can be used to treat the full particle dynamics with a considerable increase in computational speed, and they compare favorably against current experimental data. He also discussed the relevance of Bohm quantum mechanics in the wider context of correlated quantum systems.
DIII-D and ITER: Latest experimental plans and diagnostic development
April 25, 2019
Rejean Boivin
General Atomics
The presenter discussed the DIII-D program’s latest experimental campaign, which will include new tools in support of the development of Advanced Tokamak research and the study of boundary solutions for fusion reactors. Many of these new tools aim at developing efficient mechanisms for current drive. In parallel, new diagnostics have been added and upgraded, allowing further testing of models and theories. In addition, progress has been made on the design, fabrication and assembly of the ITER device, remaining on track for the first plasma operation scheduled for 2025-2026. Diagnostic developments have reached levels where techniques can be applied or transferred to ICF devices. The presentation included a description of imaging polarimetry, divertor viewing systems, and gamma ray imaging.
Isentropes extracted from proton-heated warm dense matter using streaked X-ray radiography
April 18, 2019
Matthew Hill
Atomic Weapons Establishment, United Kingdom
Obtaining off-Hugoniot data to improve equation of state models in the warm dense matter regime remains a high priority for HED science, but generating and diagnosing matter in this state to sufficient resolution has proved challenging. A series of laser-driven proton heating experiments conducted at the AWE Orion laser facility have achieved uniform isochoric heating to 5-10 eV in solid density boron carbide, plastics and diamond, with streaked X-ray radiography providing few-picosecond-resolution time-resolved density profiles of the subsequent isentropic expansion. Combined with ion spectra and streaked optical pyrometry, it is possible to construct model-independent isentropes from these data using a method published by M. Foord et al. and compare them to commonly used LEOS, SESAME and NuQEOS predictions. We find that at solid density all three models agree with the data to within experimental uncertainty, but at lower densities the data suggest they under-predict the pressure by as much as an order of magnitude.
New approaches to temperature-dependent density functional approximations
April 11, 2019
Aurora Pribram-Jones
University of California, Merced
Thermal density functional theory is common in simulations of high-temperature, high-density materials, despite the scarcity of explicitly temperature-dependent electron interaction free energy approximations and disagreement over the impact of these missing thermal effects on calculated properties. Insights from both ensemble density functional theory and the electronic strong-interaction limit can be applied to thermal ensembles, creating new approximation schemes and serving to connect these branches of formal theory with thermal density functional theory and its applications. Numerical demonstrations using the finite-temperature asymmetric Hubbard dimer and the uniform electron gas will be used to examine the advantages and disadvantages of the two approaches.
Fluid silicates at extreme conditions and the magma ocean
March 21, 2019
Lars Stixrude
University of California, Los Angeles
The Earth may have begun in a completely molten state, a global magma ocean, with silicate liquid extending from a dense silicate atmosphere to the boundary with the iron-rich core at a pressure of 140 GPa. Deep melt may exist in the Earth today, and the magma ocean may have left signatures of its presence. However, these signals are still uninterpretable because of a lack of basic knowledge of the behavior of fluid silicates at extreme conditions. To help answer fundamental questions, we have performed first principles quantum mechanical simulations in the range of pressure, temperature, composition relevant to the early Earth that have not yet been explored by experiment or theory. Simulations of liquid, vapor, and supercritical forms lend new insight into the crystallization history of the magma ocean, evaporation at its surface, and the possibility of a silicate dynamo early in Earth’s history.
Simulations of dense hydrogen with quantum Monte Carlo
March 14, 2019
David Ceperley
University of Illinois, Urbana-Champaign
Hydrogen accounts for much of the visible mass in the universe. Even though hydrogen is the first element in the periodic table, calculating its properties is not simple since both the electronic and protonic correlations are quantum and correlated. It has long been an open question how hydrogen makes a transition from a molecular insulating state to an atomic metallic state. We use a quantum Monte Carlo method (Coupled Electron Ion Monte Carlo) where we start with the true interaction between the electrons and protons and treat both fully quantum mechanically. With this method we have studied molecular dissociation in liquid hydrogen and have observed clear evidence of a liquid-liquid phase transition. During the past few years, several experiments have reported observations of the transition we predicted.
Overview of the Scarlet Laser Facility and the OSU high energy density physics group
March 7, 2019
Douglass Schumacher
Ohio State University
The Scarlet Laser Facility, built with support from the U.S. Department of Energy, is a 300 TW system delivering pulses up to 10 J in energy with durations as short as 30 fs. It is used to study the intense laser matter interaction from the damage threshold up to the creation of highly relativistic plasmas. The presenter described his recent work on structured targets that enhance the laser-plasma interaction, the mechanisms of laser-based ion acceleration, and plasma mirror physics. In addition, he discussed a new technology based on liquid crystals that rapidly forms films as thin as 20 nm for targets and plasma mirrors for high repetition rate, petawatt class lasers. In addition to showing particle-in-cell simulation (PIC) results in support of this work, he described a new approach to PIC modeling that incorporates atomic pair-potentials into the PIC cycle. His research team is using this code to study laser damage and hope to extend it to a more general study of warm dense matter.
How artificial intelligence can advance inertial confinement fusion
February 28, 2019
Luc Peterson
Lawrence Livermore National Laboratory
Advancements in artificial intelligence technology are impacting scientific research in fields as diverse as drug discovery and fluid turbulence. Research in inertial confinement fusion (ICF) could also benefit from these technological advances. However, the challenges of ICF place some burdens on the immediate applicability of artificial intelligence. During this talk, the presenter discussed some of those challenges, such as data scarcity and the interdependence on computational modeling. In addition, the discussion explored how we are working to overcome these challenges to accelerate progress towards ignition.
February 7, 2019
Suxing Hu
University of Rochester
First-principles methods for quantum many-body systems, such as path-integral Monte Carlo (PIMC) and density functional theory (DFT) can provide a self-consistent way to predict material properties with the possibility of systematic improvement of their calculation accuracy. In particular, thermal DFT has revolutionized simulation and understanding of high-energy-density (HED) physics and chemistry over the past two decades. DFT-based quantum molecular-dynamics (QMD) has helped generate accurate predictions of static, transport, and optical properties of materials under HED conditions. In recent years, time-dependent DFT started to play a crucial role in studying dynamic and transport physics in HED plasmas. In this talk, the presenter discussed (1) the HED physics we have learned from PIMC and DFT-based QMD calculations; (2) how these first-principles results impact on our understanding of inertial-confinement fusion implosions and HED experiments in general; and (3) what challenges we are facing to further improve physics predictions of DFT for HED plasmas.
Opacity of shock-heated boron plasmas
January 31, 2019
Walter Johnson
Notre Dame University
Standard measures of opacity, the imaginary-part of the atomic scattering factor, f2, and the mass attenuation coefficient are evaluated in shock-heated boron, boron carbide, and boron nitride plasmas. The Hugoniot equation, relating the temperature behind a shock wave to the compression ratio across the shock front, is used in connection with the plasma equation of state to determine the pressure, effective plasma charge Z, and the K-shell occupation in terms of the compression ratio. Solutions of the Hugoniot equation reveal that the K-shell occupation in low-Z ions decreases rapidly from 2 to 0 as the temperature increases from 20eV to 500eV; a temperature range in which the shock compression ratio is near 4. The average-atom model is used to determine K-shell and continuum wave functions and the photoionization cross section for x-rays in the energy range from 1 to 10 keV, where the opacity is dominated by the atomic photoionization process. For an uncompressed boron plasma at 10 eV, where the K-shell is filled, the average-atom cross section, the atomic scattering factor and the mass attenuation coefficient are all shown to agree closely with previous (cold matter) tabulations. For shock-compressed plasmas, the opacity is found to be well approximated by scaling the cold-matter values by the relative K-shell occupation; however, there is a small correction to this rule caused by the energy dependence of the photoionization cross section. Attenuation coefficients, for a 9 keV x-ray are illustrated as functions of temperature along the Hugoniot for B, B4C, and BN plasmas.
Kinetic physics of magnetized plasmas and its impact on pulsed-power HED experiments
January 24, 2019
Genia Vogman
Lawrence Livermore National Laboratory
Pulsed-power experiments run mega-amps of current through a load to produce and study high-energy-density matter. Experimental results show that the formation of low-density plasmas in the power feeds gives rise to parasitic currents, which affect load dynamics and prevent scaling of load parameters. To understand the inimical transport properties of these low-density, magnetized, collisionless plasmas and how they affect experimental outcomes, the environment within the power feeds is studied using high-order time-dependent continuum kinetic simulations, which offer enhanced solution accuracy and can robustly capture equilibria. The effects of drifts, anisotropies, finite Larmor motion, and sheared flow instabilities are examined. The computational study is facilitated in part through the development of machinery for constructing self-consistent kinetic equilibria and through the generalization of existing fluid theory analysis.
Charged-particle stopping power in dense plasmas
January 10, 2019
Alex Zylstra
Lawrence Livermore National Laboratory
As an energetic charged particle moves through plasma, it loses energy to the background electrons and ions; the rate of energy loss dE/dx is known as the stopping power. Sufficiently accurate stopping power models are required to model charged-particle transport in systems of interest, such as in ICF hot-spot ignition and burn propagation into the dense fuel where the DT as provide self-heating, or for secondary/tertiary neutron production in the ICF dense fuel. Calculating the stopping power in these regimes is a theoretical challenge, especially near the maximum in dE/dx (the ‘Bragg peak’) or in degenerate/strongly-coupled plasmas. In the past several years a few benchmark experiments have begun to provide direct measurements of dE/dx in ICF-relevant plasmas for the first time. This talk provided an overview of the results compared to several models.
Building a Multi-Phase Equation of State: A Concrete Example Illustrating Both Fun and Frustration
December 20, 2018
Lorin Benedict
Lawrence Livermore National Laboratory
Proper interpretations of high-energy density experiments require the knowledge of the energy of states (EOS) of the constituent materials. When very detailed information is desired from such an experiment, the EOS models must be correspondingly detailed. This seminar will walk through a particular example of current interest – the experimental determination of the multi-Mbar melt curve of iron – and discuss how we are attempting to build a limited-range multiphase Fe EOS to aid in the estimation of the temperature in ongoing shock-ramp experiments. This step-by-step walkthrough of the experimental construction will convey both the fun and the frustration of building an EOS model from disparate sources of experimental data and ab initio predictions.
Nucleation of Ice VII Under Exoplanetary Conditions
December 13, 2018
Jonathan Belof
Lawrence Livermore National Laboratory
This seminar discusses a recently developed physics-based solidification model for extreme conditions that can successfully resolve the experimental discrepancies regarding the solidification of water into the high-pressure ice VII phase. Experiments using dynamic diamond anvil cell, pulsed-power, and gas-gun platforms have presented contradictory results regarding nucleation of ice far from equilibrium. The model discussed was constructed with a focus on the role of symmetry, mass, and thermal transport at the liquid/ice interface and requires the inclusion of new aspects unique to the non-equilibrium state. The model also makes new predictions and suggests possible future experiments that have the potential to settle important questions governing the fundamental principles of nucleation far from equilibrium.
Systematic Measurements of Opacity Dependence on Temperature, Density, and Atomic Number at Stellar Interior Conditions
December 06, 2018
Taisuke Nagayama
Sandia National Laboratories
This seminar discusses a new analysis of opacity at differing temperatures and densities of chromium, iron, and nickel and the implications of the results on the discrepancy between model predictions of iron opacity versus the measurements of opacity at matter conditions similar to the boundary between solar radiation and convection zones. Calculated iron opacities have shown narrower spectral lines, weaker quasi-continuum at short wavelength, and deeper opacity windows than measurements. The collection of measured opacities in the study discussed provides constraints on hypotheses to explain the discrepancy.
Predictive Simulations of Dynamically Compressed Materials
November 08, 2018
Ivan Oleynik
University of South Florida
This seminar discusses the recent progress in predictive atomic-scale simulations of materials dynamically compressed by shock waves. Extending the time and length scales of shock wave molecular dynamics simulations and developing high-fidelity interatomic potentials specially designed for simulations of extreme conditions has revealed several new phenomena: single two-zone elastic-plastic shock wave, observation of orientation-dependent solid-liquid phase transition pathways towards orientation-independent final equilibrium states, and novel polymorphic phase transitions in shock-compressed diamond. Further discussion covers the challenges and opportunities in predictive simulations of dynamical compression of materials and the dynamic interplay between theory and experiment.
The High Energy Density Science Center: A Progress Report
October 25, 2018
Frank Graziani
Lawrence Livermore National Laboratory
The High Energy Density Science Center was established in late 2015 through a joint agreement between the Physical and Life Sciences, Weapons and Complex Integration, and NIF and Photon Science Directorates. The goal of the Center is to build a high energy density community by supporting and collaborating with academic partners and integrating those efforts into the programs at LLNL. The Center is built around four focus areas: education, workshops and seminars, workforce pipeline to the programs, and enabling research collaborations between LLNL and academic partners. This seminar presents the current activities of the Center, including on-going collaborations with UCSD and UC Berkeley; new interactions with Florida A&M University, Osaka University, and Michigan State University; the present and future of the education program; the sabbatical program; interactions with the programs; and outreach opportunities to universities.
Simulation of Non-Linear Electronic Response in Electron-Ion Interactions, from Electronic Stopping Power to Molecular Dynamics with Electron-Phonon Coupling
October 18, 2018
Alfredo A. Correa
Lawrence Livermore National Laboratory
This seminar presents simulation results regarding matter undergoing particle radiation, electron-ion thermalization, and non-linear electron conductivity. These effects remain fundamental in understanding the non-adiabatic ion-electron interaction in real materials. We employed real-time time-dependent density functional dynamics to obtain electronic stopping at low velocity for protons, alpha and heavier ions in metals and insulators, to describe phenomena that involve non-linear response and band-structure effects as well as variable ionization states. By studying the limit of low velocity limit from first principles, we propose a model that connects the stopping power and the electron-phonon regime under a single framework.
Experimental Constraints on the Composition of the Earth's Core
October 15, 2018
Yingwei Fei
Carnegie Institution for Science
This seminar discusses an integrated approach to experimentally constrain light elements in the Earth's core, such as carbon, oxygen, silicone, and sulfur, from element partitioning data, measurements of density, and measurements of sound velocity of core materials under extreme conditions by static and dynamic methods. Comparison of the seismically derived core density profile with the measured density of pure iron indicates some amounts of light elements in the core; their presence must reflect the conditions of the accretion process and silicate-metal equilibrium separation. The integrated approach presented yields a more complete understanding of the chemistry and physics of the Earth's core.
Overview of the Basic Plasma Science Facility
October 11, 2018
Troy Carter
University of California, Los Angeles
This seminar provides an overview of the research performed at the BaPSF and a discussion of recent experiments studying the modification of pressure-gradient-driven turbulence and transport by controlling cross-field flow and flow shear. This experiments were conducted in the BaPSF centerpiece, the Large Plasma Device, a 20-meter in length magnetized liner plasma device. This device has been used to study numerous fundamental processes, including collisionless shocks, dispersion and damping of kinetic and inertial Alfvén waves, flux ropes and magnetic reconnection, three-wave interactions and parametric instabilities of Alfvén waves, turbulence and transport, and interactions of energetic ions and electrons with plasma waves.
Inference of the Electron Temperature in Spherical Implosions from X-Ray Spectra
September 27, 2018
Grigory Kagan
Los Alamos National Laboratory
This seminar discusses the first study of X-ray emissions from a spherical implosion "hot-spot" with specific kinetic modifications to the electron distribution diagnostic. The current consensus is that successful diagnostic should operate with photon energies hw greater than 15 keV. Two main approaches are considered based on measuring line emission from a high-Z dopant such as krypton or the spectral continuum of 15 keV<hw<30keV from electrons scattering off the deuterium and tritium ions. However, both types of hard X-ray emissions are due to suprathermal free electrons, with a mean-free-path much larger than that of thermal electrons and a distribution that deviates from the Maxwellian, even if the bulk plasma is close to equilibrium. The study presented demonstrates new features in the emission spectrum brought about by these modifications and shows that inferring the electron temperature as if the emitting electrons are Maxwellian gives a lower value than the actual.
High Energy Lasers Race Towards Megawatt Levels
September 20, 2018
Martin Richardson
University of Central Florida
This seminar provides a review of technological progress in the field of high-energy lasers with a historical perspective and discussion on some of the challenges for transition to fully deployed defense systems. Discussion covers laser development at UCF, advanced fiber laser concepts for both Yb and Tm doped lasers operating at 1mm and 2mm respectively, limits to single-channel single-mode kW operation with with Yb fiber lasers and relevance to Tm fiber lasers, prospects for >100 kW range laser development, and new paths for laser defense applications using high-intensity ultrafast lasers in the filamentation regime.
September 13, 2018
Mari Gatu-Johnson
Massachusetts Institute of Technology
This seminar discusses the experimental design, results, and implications of recent HED experiments studying the T+T reaction and the mirror 3He+3He reaction. HED plasmas closely mimic astrophysical environments and are an excellent complement to accelerator experiments studying thermonuclear reaction rates and nuclear processes. The experiments discussed provide the first conclusive evidence of a variant TT-neutron spectrum in a center-of-mass energy spectrum between 16 and 50 keV as well as implications that the underlying physics changes with the center-of-mass energy. Future directions for exploring light-ion reactions are also discussed.
Planetary-Scale Redox Processes: Oxidation and Carbonation of Transition Metals at High Pressures and Temperatures
September 06, 2018
Abby Kavner
University of California Los Angeles
The tendency of elements to be incorporated into an iron-rich planetary core instead of oxidizing and mixing with the mantle and/or crust is determined in part by their relative abilities to oxidize or reduce at pressures and temperatures of planetary interiors. In addition to the oxidation/reduction reactions, in the presence of abundant carbon, carbonation/decarbonation reactions can also occur. This seminar presents research that begins to stake out an electrochemical series relevant for the high pressures and temperatures of planetary interiors, quantifying the tendency of major elements to either oxidize or carbonate during the planetary formation process instead of being incorporated into an iron-rich planetary core.
August 23, 2018
Bhuvana Srinivasan
Virginia Polytechnic Institute and State University
The Enigmatic Magnetic Fields of Uranus and Neptune
August 09, 2018
Sabine Stanley
Johns Hopkins University
This seminar provides an overview of planetary dynamos and a deep discussion on the numerical dynamo modeling of and possible explanations for the multi-polar surface radial magnetic fields of Uranus and Neptune. The effects of a superionic water phase and application of scaling laws that include convective shell thickness are discussed as results of 175 dynamo simulations using mMoSST. Further discussion includes implications for exoplanets and future simulations modeling superionic water layers and additional interior structures.
July 26, 2018
Carolyn Kuranz
University of Michigan
This seminar provides an overview of the experimental HED hydrodynamics program at the University of Michigan and recent experiments showing mode-coupling in Richtmyer-Meshkov experiments, suppression of Kelvin-Helmholtz growth due to compressible effects, the ablative stabilization of the Rayleigh-Taylor instability, and the use of x-ray radiography to create 2d images of instability growth to observer the evolution of these processes. Further discussion involves the consequences of hydrodynamic instabilities in HED systems and the ability to use high-energy lasers to drive these phenomena.
Applications of Laser Wakefield Accelerators
July 19, 2018
Alec Thomas
University of Michigan
This seminar provides a review of recent experiments in laser wakefield acceleration and energetic photon generation using the laser systems HERCULES and Lambda-cubed at the University of Michigan and the Gemini laser at the Rutherford Appleton Laboratory and discusses the future potential of the technology. Recent progress in laser wakefield acceleration has led to the emergence of new electron and X-ray sources that may have benefits for ultrafast science and imaging applications. Laser wakefield acceleration provides radiation pulses with ultrashort duration and intrinsic synchronisation with the laser source, allowing for pump-probe measurements with good temporal resolution. These pulses can be used to study ultrafast dynamical phenomena in plasma and dense material, such as transient magnetic fields, rapidly evolving plasma dynamics, and crystal lattice oscillations.
Developing Consistent Models for Matter in Extreme Conditions
June 28, 2018
Stephanie Hansen
Sandia National Laboratories
The extreme densities and temperatures accessible in modern experimental facilities alter the electronic and ionic structure of materials, leading to changes in state and transport properties that affect simulations and the interpretation of experimental data. This seminar describes ongoing efforts to generate a comprehensive set of consistent state and transport data from a single atomic model whose electrons and ions respond self-consistently to changes in local material conditions. This approach ensures that equations of state, transport properties (thermal and electrical conductivities, opacities, stopping powers), and diagnostic signatures (X-ray Thomson scattering, spectroscopic shifts and broadening) are mutually consistent. Such consistency can help to constrain simulations and may improve the reliability of data interpretation from complex experiments.
At-Parameter Experimental Astrophysics: The Wootton Center for Astrophysical Plasma Properties
June 21, 2018Don Winget
University of Texas at Austin
This seminar discusses the "at-parameter" experiments at the Wootton center that recreate the plasma conditions found in astronomical objects, thereby extending the reach of astronomy from the purely observational to the experimental. Current experiments investigate the weaknesses in stellar opacities, the unknown atomic physics of black hole accretion disks, and the uncertainties in line-broadening models for white dwarf stars. An in-depth discussion is presented on the latter with a discussion of the impact of these experimental capabilities on astronomical study.
June 14, 2018
Andrew Baczewski
Sandia National Laboratories
An increasingly popular application of electronic structure theory is the parameterization of material models used in laboratory astrophysics, inertial confinement fusion, and planetary science. However, transport properties that are also vital to these applications have received somewhat less attention as a target for development. This seminar discusses the important opportunities available to test theory and code against observables beyond thermochemistry, with particular focus on recent experimental results from Sandia laboratory that probe transport properties in the warm dense regime using the time-dependent density functional theory in describing X-ray Thomson Scattering experiments.
The Multispecies BGK Model: From Theory to Applications to Multiscale
May 17, 2018
Michael Murillo
Michigan State University
This seminar discusses the exploration of BGK models specifically for mixtures in four distinct areas. The MSU formulation of BGK as a multitemperature model with an emphasis on the H-theorem is discussed and compared to other, similar formulations. Numerical solutions for interface mixing in an ablator-ice interface based on a multiphysics version of BGK are presented. The presenter describes how the MSU BGK model can be extended to quantum systems, allowing exploration of electronic transport processes in dense plasmas, and how to obtain a near MD-level of accuracy in BGK via a heterogeneous multiscale approach that couples MD to BGK models.
Magnetars, Electromagnetic Pulses, and Fast Radio Bursts
May 3, 2018
Roger Blandford
Stanford University
This seminar discusses the ongoing research on the properties of electromagnetic pulses produced by flares from magnetars, with emphasis on the high-energy density features. Such electromagnetic disturbances have the potential to steepen and produce fast radio bursts. These raise interesting questions concerning the behavior of magnetic fields and plasma under enormous energy densities and involve quantum electrodynamics beyond the Schwinger field.
Dense Plasma Modeling with Average Atoms, KKR, and the Potential of Mean Force
April 19, 2018
Charlie Starrett
Los Alamos National Laboratory
In this three-part seminar, the presenter discusses recent implementations of an Inferno/Purgatorio-like average atom model using a hybrid Green's function/orbital-based approach, a new method for equation of state prediction of dense plasmas using the KKR-Green's Function method, and a new computationally inexpensive approach to calculating the electrical conductivity of dense plasmas using a Potential of Mean Force in a relaxation time approximation. Further discussion covers the advantages and comparisons of these models to existing methods.
Dark Matter Searches and Laser Physics
April 5, 2018
Marianna Safronova
University of Delaware
This seminar provides a detailed discussion of current and future efforts aimed at dark matter detection enabled by laser technologies. Particular focus is on "light-shining-through-walls" experiments using resonant laser power build-up in large-scale optical cavities and on experiments using optical clocks with ultrastable lasers to search for a broad class of ultralight dark matter.
Magnetic Fields in the Cosmos: How Laser-Driven Experiments Can Shed Light on Turbulent Dynamo
March 22, 2018
Petros Tzeferacos
University of Chicago
This seminar provides a detailed discussion of the simulations, design, results, and interpretations of a series of high-power laser experiments conducted at Omega and NIF to study the dynamo amplification of magnetic fields. The properties of the fluid and the magnetic field turbulence are characterized using a comprehensive suite of plasma and magnetic field diagnostics. Large-scale 3D simulations were conducted to design and interpret the experiments using the radiation-MHD code FLASH on Mira at Argonne National Laboratory. Further discussion covers the results of the experiments which indicate that magnetic Reynolds numbers above the expected dynamo threshold are achieved and seed magnetic fields and are amplified by turbulent dynamo.
Modelling Stellar Explosions and Nucleosynthesis
February 22, 2018
Carla Frohlich
North Carolina State University
This seminar provides detailed discussions on research and simulation results using the PUSH method to better predict nucleosynthesis during core-collapse supernovae and to explore the fate of hyper-massive stars during pair-instability supernovae that may result in a superluminous transient. The PUSH method is a computationally efficient method that allows explosions to be induced in otherwise non-exploding, spherically symmetric models. Results from the first pair-instability supernova simulations performed in 3d are also presented.
ACHIP: Laser Accelerators on a Chip International Program
February 8, 2018
Robert Byer
Stanford University
This seminar details the progress of the Moore Foundation funded ACHIP collaboration to demonstrate a laser-driven accelerator on a chip. To date the collaboration has demonstrated greater than 800 MeV/meter gradient in a fused silica grating structure and has demonstrated the first accelerators based on silicon. The collaboration continues to make progress toward a 100 MHz repetition-rate accelerator with attosecond electron bunches to enable applications in science and medicine.
Making Strongly Magnetized Jets and Gamma-Ray Bursts in the Laboratory
February 1, 2018
Edison Liang
Rice University
This seminar reviews two recent advances in the study of high-energy astrophysical phenomena using lasers. Discussion focuses on experiments using the OMEGA laser to form a ring pattern irradiating a flat target to launch well-collimated supersonic jets with MG imbedded helical magnetic fields and on experiments using the Texas Petawatt and Trident lasers to irradiate high-Z solid targets to create dense gamma -ray and electron-positron jets similar to those found in cosmic gamma-ray bursts. Further discussion covers the experiment results and their agreements with simulation predictions, future experiments on the microphysics of cosmic gamma-ray bursts, and the potential fundamental physics and technological applications of dense gamma-ray and positron sources.
Transport of Intense Proton Beams Driven by Intense Lasers
January 25, 2018
Chris McGuffey
University of California, San Diego
This seminar describes experimental methods for delivering intense proton beams to heat a secondary target and showcases simulations that investigate intensity-dependent transport phenomena in warm targets. In existing kilojoule, petawatt-class lasers, the proton beams have picoseconds duration and can be focused to <100 microns and also have sufficient energy to be the pump in innovative experiments such as isochoric heating to warm (>100 eV) dense matter states. Beams with double-digit MeV particle energy can be produced that have orders of magnitude more charge than conventional accelerator facilities.
Transport Properties of Dense Plasmas
January 11, 2018
Scott Baalrud
University of Iowa
This seminar discusses recent advances that have extended plasma kinetic theory to address ion transport in dense plasmas, where ions are moderate to strongly coupled and electrons are Fermi degenerate. First principles numerical techniques are the primary method used to calculate the transport properties of warm and hot dense matter, but they are often too computationally expensive to provide the data input required for hydrodynamic simulations of experiments that traverse a wide range of density, temperature, and material composition. Results are compared with state-of-the-art orbital-free density functional theory computations, revealing that the theory is accurate from high temperature through the warm dense matter regime, breaking down when the system exhibits liquid-like behaviors. Recent results addressing the influence of strong magnetic fields are also discussed.
Roberto Mancini
University of Nevada, Reno
December 14, 2017

Atomic physics of high-energy density and radiation-driven plasmas
Atomic physics impacts emission and absorption of radiation in plasmas as well as energy deposition and transport, playing a key role in both modeling and diagnosis of plasmas. Inertial confinement fusion x-ray spectroscopy relies on collisional-radiative atomic kinetics, detailed Stark-broadened spectral line shapes, spectroscopic quality radiation transport, and advanced data analysis techniques. The seminar will discuss the analysis of spatially averaged and resolved plasma conditions in implosion cores, the state of the unablated compressed shell, the migration of shell tracer into the core, and the application of multi-objective data analysis driven by a Pareto genetic algorithm. In laboratory photoionized plasma experimentsperformed at the Z Machine, a gas-cell filled with neon was irradiated with a burst of x-ray flux emitted by a wire-array z-pinch. We modeled the spectral distribution of the x-ray drive impinging on the gas-cell, Boltzmann electron kinetics to study photoelectron thermalization and the electron distribution function, and radiation-hydrodynamic simulations with inline collisional-radiative atomic kinetics. To compute electron temperatures consistent with observation, the details of the photon-energy distribution of the drive, x-ray attenuation through the cell’s window, and collisional-radiative atomic kinetics coupled to the x-ray flux need to be taken into account. Opportunities for research collaboration in theory and modeling as well as data interpretation and analysis will be emphasized.
Richard Dendy
Warwick University
November 16, 2017
Fusion-born alpha-particles as an intense collective radiation source: from JET and TFTR to ITER
The central physics objective of fusion research is to confine fusion-born ions long enough for their energy to keep the plasma hot. Measuring the properties of these ion populations was a standing challenge for deuterium-tritium plasmas in the Joint European Torus (JET) and the Tokamak Fusion Test Reactor (TFTR), and remains so for ITER. Fortunately, there is an initially unexpected, but widespread, tendency for spatially localized inversions in the velocity distribution of fusion-born ions to arise naturally in large Magnetic Confinement Fusion (MCF) plasmas. The associated free energy is released in the form of intense (orders of magnitude times black-body) spectrally structured radiation: ion cyclotron emission (ICE). Understanding the fast (a few ion gyroperiods) collective relaxation process whereby ICE is generated is essential for the exploitation of ICE as a diagnostic for fusion-born ion populations. Progress has been good, but intermittent: it includes pioneering analytical predictions by Soviet scientists in the 1970s; extended analytical studies in parallel with JET and TFTR D-T experiments in the 1990s; and direct numerical simulation using particle in cell/hybrid codes at present [1,2]. The dearth of D-T MCF plasma experiments for ICE studies since 1998 has been relieved by abstruse energetic ion populations in contemporary Korean and Japanese experiments: fusion-born protons in Korea Superconducting Tokamak Advanced Research (KSTAR) deuterium plasmas [2] and sub-Alfvénic neutral beam ions in the Large Helical Device (LHD). These relax by generating ICE in interesting yet explicable ways in the presence of superb modern diagnostics. Operating ICE “in reverse” [3] could channel alpha-particle energy to the core of the plasma.
Ronald Redmer
University of Rostock
November 9, 2017

Warm dense matter – probing planetary interiors
The behavior of warm dense matter (pressures up to the TPa region and temperatures up to several eV) is of paramount importance for understanding the interiors, evolution, and magnetic fields of solar and extrasolar planets. While the light elements H and He are the main components of gas giants such as Jupiter, mixtures of C-N-O-H are relevant for Neptune-like planets, and minerals of the MgO-FeO-SiO2 complex are the building blocks of rocky planets (Earth and super-Earths). However, the high-pressure phase diagram of these elements and mixtures is not well known, particularly the slope of the melting curve. Furthermore, insulator-to-metal transitions and phase separation may occur in warm dense matter. These high-pressure phenomena have a strong impact on interior, evolution, and dynamo models for planets, and constitute a major challenge to high-pressure, plasma, and computational physics.
Molecular dynamics simulations based on finite-temperature density functional theory are used to predict the equation of state, the high-pressure phase diagram, and the transport properties of warm dense matter for a wide range of densities and temperatures typical for the interior of planets. These data are benchmarked against diamond-anvil-cell and shock-wave experiments and then applied to construct interior and evolution models for solar and extrasolar planets.
Frank Graziani
Director, High Energy Density Science Center
November 2, 2017

The High Energy Density Science Center: A Vision for the Future
The High Energy Density Science Center (HEDSC) was established in late 2015 through a joint agreement between the Physical and Life Sciences, Weapons and Complex Integration, and NIF and Photon Science Directorates. The Center’s goal is to build a high energy density community through support of, and collaboration with, academic partners and integrating those efforts with the programs at Lawrence Livermore National Laboratory (LLNL). The Center is built around four focus areas: (1) education, (2) workshops and seminars, (3) workforce pipeline to the programs, and (4) enabling research collaborations between LLNL and academic partners. In this talk, we will present the current activities of the Center, including the interactions with the University of California, San Diego through the University of California Office of the President award and recent results from the strategic planning process.
Goetz Lehmann
Institute for Theoretical Physics, Heinrich Heine University
September 28, 2017

Plasma-based Amplification and Manipulation of High-power Laser Pulses
In the last decade, the increasing availability of terawatt- and petawatt-class lasers with pulse durations on the order of 10 to 100 femtoseconds has intensified interest in the relativistic interaction between laser radiation and matter. Today laser intensities up to 1022 W/cm2 can be achieved. Most high-intensity lasers today rely on amplification schemes that can barely be scaled to higher power levels due to material damage thresholds. An alternative approach that allows circumventing these issues is the use of plasma as an amplification medium. In the presentation, Prof. Lehmann discusses Brillouin-type plasma-based laser amplifiers and show that the ion plasma waves, driven by the two laser pulses, eventually form photonic crystals.
Dirk Gericke
Center for Fusion, Space, and Astrophysics, University of Warwick
September 21, 2017

The Relaxation Cascade in Driving High-Energy Density Matter
High-energy-density matter (HEDM) in the laboratory is usually created in states far from equilibrium as the large energy input needed for ionization and heating drives particles into specific states and distributes the energy unevenly between the species. The pathways to equilibrium, or at least the relaxation times, are therefore very important for interpreting most experiments. This talk will review the different stages of the equilibration process that span the time scales from femtoseconds, for establishing an equilibrium distribution for the electrons, to nanoseconds, for material rearrangements. Special focus is given to the effects of strong interactions inherent to HEDM. Finally, the nonequilibrium physics discussed is applied to a number of recent experiments.
Franklin Dollar
Department of Physics and Astronomy, UC Irvine
September 14, 2017

Ultrafast Laser-driven Probes for Investigating High Energy Density Physics
Intense laser-plasma interactions are a robust source of radiation pertinent for investigating matter in extreme conditions, as evidenced by the Matter in Extreme Conditions beamline at the SLAC National Accelerator Laboratory and the Advanced Radiographic Capability beamline at NIF. Experiments showcasing the use of short-pulse lasers to create bright soft x-rays with circular helicity, white-light spectrum radiation suitable for near-edge x-ray absorption fine structure radiography, and radiography using high-energy electrons will be presented. Dynamic measurements of nano-plasmas will also be presented.
Emily Carter
School of Engineering and Applied Science, Princeton University
August 31, 2017

Atomic-Scale Assessment of First-Wall Materials for Fusion Reactors: Insights and Challenges for Materials Simulations
Quantum mechanics–derived computer simulations can provide insights into the survivability of first-wall and divertor materials in prototype magnetic confinement fusion reactors. I present results of research aimed at assessing how hydrogen isotopes interact with solid tungsten and liquid lithium, candidates for plasma-facing components of fusion reactors. The research utilizes both standard Kohn-Sham density functional theory (KS-DFT) as well as orbital-free (OF) DFT. Over the last two decades, my research group has advanced the latter theory in terms of accuracy and efficiency. Our open-source code PROFESS exhibits quasilinear scaling with a small prefactor, rendering it orders of magnitude faster than KSDFT, thereby enabling significantly larger system-size (static and dynamic) simulations. The method also now works on leadership-class petascale computers (Titan at ORNL). However, OFDFT relies on kinetic energy density functionals, which at this point are still only as accurate as KSDFT for main group semiconductors and metals. Ongoing work aims to alleviate this problem, which ultimately should extend OFDFT to the rest of the periodic table.
Michael Zingale
Department of Physics and Astronomy, Stony Brook University
August 10, 2017

Modeling Stellar Explosions with the AMReX Astrophysics Suite
The seminar will describe ongoing simulations of Type Ia supernovae and x-ray bursts. Type Ia supernovae are the brightest thermonuclear explosions in the present-day universe, and are important for nucleosynthesis and measuring distances in cosmology. To date, however, there is no consensus on what the pre-explosion system looks like. The popular progenitor models, along with their strengths and weaknesses, will be discussed, along with the work being done to understand them. X-ray bursts provide a different set of challenges to the modeler, but ultimately, they can help us understand the nuclear equation of state. Stony Brook’s simulations use the publicly-available adaptive mesh refinement codes Castro and Maestro, built on the AMReX library. Maestro models subsonic stellar flows, while Castro focuses on highly-compressible flows. These codes share the same microphysics (reaction networks, equations of state) and parallelization strategy. In addition to the science results, the development of these codes for next generation architectures, including GPU-based supercomputers, will be discussed.
Warren Mori
Departments of Physics and Astronomy and Electrical Engineering, University of California at Los Angeles
July 27, 2017

Exaflop, Petawatt, and Terabar Physics
Exaflop (1018 flop) computers are on the horizon. These computers are complex and expensive instruments that require significant preparation in developing software and analysis methods to use effectively. They have the potential to dramatically advance the rate of scientific discovery. Two areas where petaflop computers are impacting plasma physics research are plasma-based acceleration and the nonlinear optics of plasmas, both of which are part what is called high-energy-density (HED) plasma physics. In plasma-based acceleration, electrons or positrons surf plasma wave wakes excited by petawatt lasers or particle beams at rates in excess of 50 GeV/m (three orders of magnitude higher than current accelerator technology). At the National Ignition Facility (NIF), the fuel is to be compressed to hundreds of gigabars of pressure, causing ignition. It is essential that the laser energy hit and be absorbed into x-rays where it is aimed for such compression to be achieved.
Pisin Chen
Leung Center for Cosmology and Particle Astrophysics, National Taiwan University
July 20, 2017

Tabletop Analog Black Holes to Investigate Information-Loss Paradox
The question of whether Hawking evaporation violates unitarity, and therefore results in the loss of information, remains unresolved since Hawking's seminal discovery in 1974. So far the investigations remain mostly theoretical, as it is almost impossible to resolve this paradox through direct astrophysical black-hole observations. The seminar will describe how relativistic plasma mirrors can be accelerated drastically and stopped abruptly by impinging ultra-intense x-ray pulses on solid plasma targets with a density gradient. This is analogous to the late-time evolution of black-hole Hawking evaporation. An experimental concept will be proposed, and a self-consistent set of physical parameters is presented. Critical issues such as black-hole unitarity may be addressed through the measurement of the entanglement between the Hawking radiation and partner modes.
Farhat Beg
Department of Mechanical and Aerospace Engineering, University of California at San Diego
June 29, 2017

Fast Ignition: The Good, the Bad, and the Ugly
The fast ignition (FI) concept for inertial confinement fusion (ICF) has the potential to provide a significant advance in the technical attractiveness of inertial fusion energy. In FI, compression of the fuel to high density and heating are achieved in separate processes. Similar to conventional ICF, a number of long-pulse lasers compress a shell to create a high-density fuel plasma. The requirements on the symmetry of the target are less stringent in FI compared to conventional ICF due to the external heating source. In addition, higher gain is expected with the FI scheme because more fuel mass can be burned with less compression energy. This scheme involves some of the most challenging and complex physics of laser-matter interactions and energetic particle transport in varying density plasmas. In recent experiments and modeling, critical issues pertinent to electron source, transport through plasma, and target design have been identified. Experimental and integrated modeling provided detailed characterization of these issues and enabled validated measurements of total coupling of the laser energy to the compressed core.
Siegfried Glenzer
SLAC National Accelerator Laboratory
May 25, 2017

Visualizing the Transformation of Matter in Extreme Conditions
At the SLAC National Accelerator Laboratory, we have developed powerful ultrafast pump-probe techniques to measure the structural transformations and the physical properties of matter in extreme conditions. We apply enormous pressures to our samples using high-power laser irradiation followed by x-ray laser pulses from the Linac Coherent Light Source to take split-second photographs of the states that result. This seminar describes our experiments that visualize compression, solid-solid phase transitions, and the formation of warm dense matter. These experiments deliver data of unprecedented accuracy that allow critical experimental tests of theory in the challenging near-Fermi degenerate regimes or in the non-ideal plasma state. Recently, we complemented our x-ray probing capability with high-energy electron diffraction techniques to investigate isochorically laser-heated matter. This data set holds surprises; our results do not support previous claims about bond hardening in warm dense matter and resolve previously undetermined melting regime boundaries.
Sarah Stewart
Department of Earth and Planetary Sciences, University of California at Davis
May 11, 2017

Following the multicomponent phase diagram to the origin of the Moon
The giant impact hypothesis remains the leading theory for lunar origin. However, current models struggle to explain the Moon’s composition and isotopic similarity with Earth. Here we present a new lunar origin model. High-energy, high-angular momentum giant impacts can create a post-impact structure that exceeds the corotation limit (CoRoL), which defines the hottest thermal state and angular momentum possible for a corotating body. In a typical post-CoRoL body, traditional definitions of mantle, atmosphere and disk are not appropriate, and the body forms a new type of planetary structure, named a synestia. Using simulations of cooling synestias combined with dynamic, thermodynamic, and geochemical calculations, we show that satellite formation from a synestia can produce the main features of our Moon. The key to lunar origin is understanding the high energy density state of the Earth after a giant impact.
Toshiki Tajima
Department of Physics and Astronomy, University of California at Irvine
April 27, 2017

X-ray Wakefield Accelerator on a Chip
It is well established that an intense optical laser pulse can drive coherent and stable wakefields that can accelerate electrons to high energies in plasmas. The recent inventions of thin film compression of lasers and its associated relativistic compression can lead to the generation of a single-cycled optical laser pulse and its relativistically compressed single-cycled x-ray laser pulse. This introduces the possibility of an x-ray laser-driven wakefield now in materials at the solid density. We suggested nanoholed material as a possible medium. The nanoholed channel allows well collimated wakefields and avoids unnecessary collisions for the accelerated beam. Further, a corrugated nanochannel could result in wakefield-driven gamma-ray sources. Because the accelerating media in nanomaterials are now in a solid (rather than in a gas), it is easy to design the structure, although rastering over many holes may be necessary. Such precision design should further allow us to pick up ions, such as by the phase velocity gradation; or the single-cycled property of the laser could make ion acceleration more coherent.
Burkhard Militzer
Departments of Earth and Planetary Science, University of California, Berkeley
April 20, 2017

Path Integral Monte Carlo Simulations of Warm Dense Matter
The properties of materials at extreme pressure and temperature conditions are important in astrophysics and fusion science. When models for Jupiter’s interior are constructed to match gravity data from the NASA mission Juno, an accurate knowledge of the equation of state of hydrogen–helium mixtures is essential. Modern dynamic high pressure experiments typically probe megabar and gigabar pressures. In order to provide a comprehensive theoretical description of materials at such extreme conditions, results from path integral Monte Carlo simulations will be presented. Equation of state results for first-row elements including carbon, CH plastic, oxygen, water, nitrogen, and neon were derived with restricted path calculations that relied on free-particle nodes. Shock Hugoniot curves were computed and compared with experimental results. The talk will describe how bound states can be incorporated efficiently into the nodal structure, which enables the simulation of heavier elements, including sodium and silicon.
Kieron Burke
Departments of Physics and Chemistry, UC Irvine
March 2, 2017

Improving Simulations of Warm Dense Matter by Developing Thermal Density Functional Theory
In the past decade or so, quantum molecular dynamics—simulations of classical ions coupled to density functional theory (DFT) calculations for electrons—have provided unprecedented quantitative agreement between simulation and measurement for warm dense matter and tremendous insight into equilibrium and near-equilibrium processes. Routine calculations use modern density functional approximations that neglect thermal many-body effects. The talk will summarize recent efforts to generalize much ground-state DFT methodology to calculations at finite temperatures.