Plasma Science Enabling Technology, Sustainability, Security, and Exploration (2021) / Chapter Skim
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4 Extreme States of Plasmas: High-Energy Density Systems
4 Extreme States of Plasmas: High-Energy Density Systems
Pages 161-207
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From page 161... ...
Stellar interiors, planetary interiors, and supernovae can all be classified as HED matter, where the material energy density is >1011 J/m3, (or, equivalently, at a pressure of >1 million atmospheres (1 Mbar)
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From page 162... ...
High energy density physics, HEDP, begins to appear in materials at about 1 Mbar pressure. The plasma regime now known as "warm dense matter" (WDM)
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From page 163... ...
Plasma physics in the HED regime is also important to the field of quan tum materials -- systems in which interactions between atoms are dominated by quantum effects. New experimental and computational capabilities developed at HED science facilities can tune conditions to produce new phases of materi als and preserve metastable states with enhanced properties, both near and far from equilibrium.
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From page 164... ...
In order to fulfill those stockpile stewardship goals, the Plasma 2010 report listed the following require ments and benefits: • Accurate understanding of material properties in a wide range of pressure and densities; • Well-diagnosed experiments for validating codes covering solid-to-WDM to-weapon-relevant conditions; 1 National Research Council, 2007, Plasma Science: Advancing Knowledge in the National Interest, The National Academies Press, Washington, DC, https://doi.org/10.17226/11960. 2 National Research Council, 2003, Frontiers in High Energy Density Physics: The X-Games of Con temporary Science, The National Academies Press, Washington, DC, https://doi.org/10.17226/10544.
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From page 165... ...
The WDM field was poised to begin relevant work on radiative properties in intense magnetic fields, particularly relevant to white dwarf conditions. HED PHYSICS -- DYNAMIC WITH BROAD IMPACT The applications of HED science span a tremendous range.
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From page 166... ...
These proton radiographs from an experiment on the Omega laser at the Laboratory for Laser Energetics show the creation of magnetic fields, in two counterpropagating plasma flows, due to the Weibel instability. Such magnetic fields are believed to be responsible for the creation of shocks in a plasma where the mean free paths of the particles are large (collisionless plasmas)
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From page 167... ...
These are critical issues to understanding the formation and evolution of these astrophysical objects, yet their properties cannot be directly observed. In this pressure regime, which combines classical solid state and plasma physics, first-principles material properties calculations are required.
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From page 168... ...
This class of plasma physics relevant nuclear reactions can be explored using modern HED experi mental capabilities. Light-ion fusion reactions are an important topic to both basic nuclear physics and astrophysics.
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From page 169... ...
Opacity experiments are challenging to perform because they require precise un derstanding of the laboratory drive and equation of state in addition to high precision spectroscopy and control over experimental conditions. As such, techniques developed and measurements made of opacities in HED physics are critical to a wide range of fields, including solar and stellar physics, astrophysics and stockpile stewardship.
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From page 170... ...
SOURCE: Courtesy of Hui Chen, Lawrence Livermore National Laboratory, Frederico Fiuza, SLAC National Accelerator Laboratory, and Bruce Remington, Lawrence Livermore National Laboratory. IGNITION, INERTIAL FUSION ENERGY, AND STOCKPILE STEWARDSHIP Inertial fusion energy (IFE)
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From page 171... ...
In this context, energy gain is fusion energy compared to the total facility energy.) These capabilities are well beyond the capa bilities of existing ICF drivers which have pulse repetition rates from 1 per hour to 1 per day.
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From page 172... ...
(a) Indirectly driven ICF target, with laser beams striking the inside of a gold cylinder (hohlraum)
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From page 173... ...
In order to fulfill its stewardship mission, NNSA listed strategic objectives of the Science Program. Specific objec tives relevant to HED science for stockpile stewardship include: • Enhanced capabilities will need to be developed to recreate more weapon like conditions in experimental facilities; • Focused experiments such as material characterization at HED conditions will be needed to support annual assessments; • HED conditions will be needed to understand the impacts on performance of aging and of new materials and processes; • Promote academic alliances to recruit and train new generations of scien tists; and • Evaluating the HED plasma environment requires innovative, sophisticated diagnostics.
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From page 174... ...
Science-based stockpile stewardship requires a uniquely trained and mentored workforce, which is best produced by actually researching HED physics, computationally and ex perimentally. It is difficult to imagine maintaining the technical expertise required for science-based stockpile stewardship in the absence of university programs in HED physics.
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From page 175... ...
Universities are not provided a sufficient level of resources and attention in several technical areas relevant to ICF and HED physics, making it difficult to provide for future workforce needs, particularly where there are citizenship requirements. One such area is pulsed power-driven HED science and technology.
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From page 176... ...
Myatt, D.H. Edgell, et al., 2012, Laser–plasma interactions in direct-drive ignition plasmas, Plasma Physics and Controlled Fusion 54:124016.
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From page 177... ...
approach to ICF also has the potential to provide the high fusion yield required both for stockpile stewardship and for IFE. In LDD approaches laser beams are focused onto the surface of the target, possibly seeding hydrodynamic instabilities.
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From page 178... ...
The programs offer opportunities for a broad range of users to perform experiments in HED science, including laboratory astrophysics, planetary science, high pressure materials science, unique regimes of plasma physics, nuclear science, and particle acceleration. These regimes are found in planets, stars, galaxies, supernova dynamics, astrophysical shocks, and accreting massive black holes.
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From page 179... ...
facility at LCLS have explored HED plasmas generated by long and short pulse lasers, using the femtosecond X-ray pulse from the LCLS. This has allowed, for example, inves tigations of warm dense matter structures and properties, nanometer-scale plasma features, dynamic phase transitions and lattice dislocations, and shock waves in materials.
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From page 180... ...
These new capabilities have significantly improved the ability of simulations to match a suite of experimental observations across a range of targets. Simulations of direct drive targets and magnetically driven targets have also increased in fidel ity and realism.
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From page 181... ...
The National Diagnostic Working Group could be expanded to officially encompass diagnostic specific to HED, technology transfer to and from midscale facilities, and data analysis and data mining techniques. Plasma Optics Since the Plasma 2010 report, plasma optics has emerged fully as a field of research.
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From page 182... ...
The paradox is that in creating larger, more uniform plasmas at higher energy density with more energetic drivers, the currently available X-ray sources (such as the SNL Beamlet backlighter and NIF's ARC petawatt laser) will be insufficient to diagnose density,
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From page 183... ...
To continue the United States lead in ICF will eventually require the next facility intended for high gain ICF to be designed and built. Given recent discoveries, whether pulsed power or laser driven, the current HED facilities and technologies are likely be inadequate to achieve high gain ICF.
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From page 184... ...
. However, for either type of device, the multiscale plasma physics required to understand and design the power coupling in a next generation machine remains a challenge to the HED physics community.
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From page 185... ...
The need for improved, more sophisticated data analysis and uncertainty quantification is being recognized by the community. In 2014, there were only two talks at the APS Division of Plasma Physics Annual Meeting that dealt with either uncertainty quantification or data mining for HEDP.
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From page 186... ...
In this field too, the United States is uniquely poised to make significant advances in laser technology, with impact well beyond ICF and HED physics. Laser Plasma Optics for ICF Ultimately, advances in LPIs will require laser pulse repetition rates or inten sities that exceed the damage limits of solid-state optical components.
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From page 187... ...
The fluence of the amplified beam was about 4 kJ/mm2, or about 300 times the damage threshold of Nd:glass in a laser amplifier. Computational HEDP and ICF The United States is a leader in the field of computational plasma physics, however the majority of that capability lies in computational tools that are not broadly available.
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From page 188... ...
With multiple bright, small, short pulse, high repetition rate X-ray sources, a fully three-dimensional evolution of the hot spot can be imaged. Another need for advanced X-ray imaging is the study of hydrodynamic instabili ties in HED plasmas.
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From page 189... ...
Matter-Electromagnetic Coupling While the plasma physics relevant to breakdown of a plasma in an intense elec tric field does not occur in the HED regime, the process is central to understanding, predicting, and designing the next generation of pulsed power machines. A higher priority must be placed on electromagnetic field-matter coupling throughout the HED community in order to better understand the low-density plasmas and plasma breakdown in pulsed power machines.
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From page 190... ...
FIGURE 4.11 Publications in HED and ICF. International collaborations are crucial to the current vibrant state of HED plasma science.
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From page 191... ...
About 60 percent of the publications during 2018-2019 were multinational collaborations. Although this is a from a fairly small sample size, it is clear that international collaborations are vital to producing high-impact work in HED physics.
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From page 192... ...
Many have direct relevance to fundamental astrophysical and material science questions. About 8 percent of the experimental time on NIF is devoted to Discovery Science projects.
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From page 193... ...
The difference between measured and calculated opacity, shown as a ratio in the bottom plot as a function of radiation wavelength, is as large as a factor of four at some energies. Replicating of this measurement (from the Z Fundamental Science Program on the Z machine)
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From page 194... ...
lasers for advanced laser plasma-based particle acceleration or study of collective plasma effects with extreme fields must be performed outside the United States. As noted in the Brightest Light report, the United States is falling behind both Europe and Asia in PW laser capabilities.
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From page 195... ...
Work on Z-machine is funded by NNSA for defense and related applications. These include producing intense UV and X-ray radiation for a variety of applications, intense magnetic fields and pressures for dynamic materials properties measurements, ICF research, stockpile stewardship, and the creation of extreme environments for astronomy experiments.
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From page 196... ...
In addition to these major, world class HED facilities there are many midscale facilities in the United States. One of the recommendations for HED science from the Plasma 2010 report was that midscale facilities needed to be maintained, ex panded, and utilized as effectively as possible.
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From page 197... ...
* Long pulse -- 2 beams, 5 kJ/beam, ns pulses University of Texas at Austin, Center Texas Petawatt Laser 140 J at 140 fs, 2 × 1022 W/cm2 for High Energy Density Science*
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From page 198... ...
The bright spots show nonuniformity in the azimuthal distribution of breakdown. COBRA one of a small group of university pulsed power machines used for basic research and training students in HED physics.
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From page 199... ...
NOTE: LTD = linear transformer drive, Marx = Marx Bank. There are three existing or planned NIF-class laser facilities outside the United States.
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From page 200... ...
As described in the 2018 Brightest Light report, most of the high-intensity lasers in the world have been (or are being) built outside the United States.
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From page 201... ...
Optimized for a hohlraum geometry, experiments at the facility are explor ing novel hohlraum geometries such as spherical hohlraums, and, shown here, a novel shape called "TACH." This design uses six small hohlraums open at one end to drive a central cavity. In this way, all the laser beams are incident at the optimum 50° angle, and the symmetry is inherently spherical, thus greatly reducing the effects of the cross-beam energy transfer laser instability and improving drive uniformity.
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From page 202... ...
RELATIONS TO AND PERSPECTIVES OF INDUSTRY In the Brightest Light report, possible industrial applications of ultrafast lasers were described, with a focus on medical applications. In order to understand, pre dict, and improve these possible applications, the HED physics of the interactions of the high-intensity lasers with their targets must be better understood.
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From page 203... ...
Quantitative understanding of the HED physics involved in the production of X-ray sources would improve the design and optimi zation of such biological and medical imaging systems.
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From page 204... ...
The High Energy Density Science Association (HEDSA) was founded in 2005 to enable academic and small business high energy density researchers to advocate for HED physics research.
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From page 205... ...
Inertial Confinement Fusion (ICF) National Diagnostics Working Group charter and workshops should be expanded to explicitly include high energy density diagnostics, interaction with midscale facilities, and data analysis and data mining techniques.
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From page 206... ...
physics at universities and midscale laser facilities should continue to expand, not only to benefit HED physics but also to maintain the critically needed HED workforce. Recommendation: Midscale pulsed-power facilities accessible to universities should be established, with leadership of these new facilities drawn from university researchers and the national laboratories.
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From page 207... ...
E x t r e m e S t a t es of Plasmas: High-Energy Density Systems 207 Recommendation: DOE-NNSA, DOE-FES, and NSF-MPS should continue and increase support for basic high energy density science programs at large facilities in collaboration with universities. Recommendation: The science program direction and the appropriate level of funding and facility support should be guided by DOE-NNSA, DOE-FES and NSF-MPS collaboratively commissioning a new high energy density physics (HEDP)
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