Fundamental Research in High Energy Density Science

High energy density (HED) science has critical applications for society from fusion energy to sustaining the nation’s nuclear deterrent, while also contributing to broader scientific questions such as understanding planets and their origins. Our new report identifies key challenges and science questions for the coming decade, and proposes ways to address them.

High energy density (HED) science is all about extremes. Imagine the temperature and pressure found in stars, at the centers of giant planets, and associated with nuclear reactions.

Materials under these conditions exhibit properties not observed in our everyday environment: nonmetals become metals, crystals take on surprisingly complex structures, and normal mass can be converted into energy.

HED science is a wide-ranging, rapidly evolving research frontier that focuses on matter where external forces, like pressure and temperature, begin to overwhelm the chemical forces of ordinary matter on Earth. Experts from astrophysics, condensed-matter and plasma physics, materials chemistry, high-pressure research, and planetary science join together to address topics ranging from security to sustainability.

HED science examines:

Hot Matter Matter at high enough temperatures to sustain nuclear fusion.

Warm Matter Matter typically at “classical” conditions. Warm Dense Matter is the subregime of this type where methods used in plasma or condensed matter physics may not be reliable in this regime.

Quantum Matter Matter exhibiting quantum behavior, often characterized by the atom or electron wavelengths exceeding the separation between atoms.

Cold Matter Matter that is not ionized by temperature. Typically solids or fluids. Often have quantum properties.

The regimes of high energy density science

Key Discoveries and Accomplishments

Spectacular breakthroughs in fundamental science and technology, experimental and theoretical capabilities, and potential impacts to society motivate today’s work in the field.

Key Science Questions for the Next Decade

The next decade of HED science will be instrumental to growing our understanding and in the development of new technologies and processes.

HED science can develop the technologies and processes required for controlling nuclear fusion in the laboratory, taking current experiments that are documenting the onset of nuclear ignition to the point of fully exploiting the output of nuclear reactions. More effective means of achieving fusion will offer a unique platform for characterizing new states of matter through experiment, simulation, and theory.

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Harnessing Star Power
Nuclear fusion powers our sun but the same extreme conditions necessary to simulate those forces on Earth will require scientific and technical advances, many of which fall within the domain of HED science.

Normally exotic materials and phenomena—such as superconductivity—may find use outside of the lab at room temperature. This would be revolutionary for technology and society. To achieve this, a concerted effort is required to integrate experiments and advance simulations, including artificial intelligence and machine learning for both quantum systems and multicomponent chemistry.

Enabling an electrified future

Enabling an electrified future
Materials exhibiting superconductivity—or perfect conduction of electric current—are possible at room temperature with higher pressure. Higher pressures can speed the onset of superconductivity. Thus, the high pressures involved in HED science are a testing ground, with several room temperature superconductors having been discovered using this method.

HED science can leverage astrophysical observations to address major questions about the evolution of the Universe, including: What is the nature of matter in the deep interiors of dead stars (“compact” astrophysical objects) throughout the Universe? Can the background of space and time (“vacuum continuum”) be broken using sufficiently intense photon densities that are now becoming available? Can we develop a quantum gravity laboratory and measure the properties of black holes (“Hawking radiation” and black-hole thermodynamics); can we emulate and understand cosmic accelerators? A key challenge for both theory and simulations is to quantitatively relate properties and processes at atomic, laboratory, planetary and astrophysical scales of distance and time.

Understanding the evolution of the universe

Understanding the evolution of the universe.
Relativistic extragalactic jets are unique phenomena, producing an array of radiation from supernova explosions and/or “black hole engines.” An example of one such jet is shown here.

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Essential Investments for Science

Due to the extreme nature of the HED science, developments in the field are dependent on cutting-edge scientific facilities.

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LEADING RECOMMENDATION
To strengthen its global leadership in high energy density (HED) science and address future national needs, the National Nuclear Security Administration (NNSA) should exploit and enhance the capabilities of its flagship HED facilities (e.g., the National Ignition Facility, Z Pulsed Power Facility, and Omega Laser Facility) by establishing plans over the next 5 years for

  1. extending, upgrading, or replacing those facilities;
  2. increasing the promotion of forefront technology development, including in high-intensity lasers;
  3. enhancing academic capabilities and mid-scale facilities; and
  4. broadening remote access to its major experimental and computing facilities.

VIEW RELATED RECOMMENDATIONS

Beyond a focus on facilities, much can be done to advance HED science with appropriate focus. Below is a list of topics and associated recommendations the committee believes will help advance the field and overcome current challenges. 

Benchmarking, in general, refers to establishing an independent standard that can be relied on to characterize the accuracy of any given model or experiment. HED science can greatly benefit from a dedicated effort to establish combined experimental and theoretical standards and benchmarks in both measurement and computation, along with robust verification and validation procedures.

  • Recommendation
    The NNSA should work with the academic and national laboratory user community, relevant government agencies, and industry to develop a high-performance computing (HPC) strategy for high energy density science over the next 2 years. This strategy should include benchmarking and the verification and validation of codes, code comparisons, the close integration of simulations using HPC with experiments, co-development of hardware and software for the research community, open-source documentation of codes and experimental results in a standardized open format (e.g., to enhance use and effectiveness of machine learning and artificial intelligence tools), and an industry-relevant implementation plan.

A major challenge has been that input energy to start nuclear fusion is required to be higher than the energy keeping apart the positively charged hydrogen ions that make up fusion fuel. To make things more difficult, hot plasmas undergoing fusion—or “burning plasmas”—are hard to confine, like steam in a kettle. Recent progress (noted earlier under “Key Discoveries and Accomplishments”) makes the next decade a crucial time for improved understanding, control, and use of burning plasmas made from Inertial Confinement Fusion (ICF).

  • Recommendation
    The inertial confinement fusion community should redouble efforts to focus on the underlying basic science to (1) achieve robust ignition and the maximum yield with optimal efficiency, (2) establish the best uses of laboratory burning plasmas, and (3) help identify the best path for future experimental and computational facilities. In particular, the sustainment of innovation and breakthrough research will require a careful balance between yield-producing and non-ignition experiments. Additionally, the NNSA should work with the relevant agencies (e.g., the Department of Energy’s Fusion Energy Sciences and Advanced Research Projects Agency–Energy and the National Science Foundation) and private industry to leverage research in inertial fusion energy and—where possible—partner in research areas of mutual interest.

There is an opportunity for the NNSA to develop partnerships with private industry in order to strengthen and broaden the HED science workforce. Doing so will also develop new technologies that are mutually beneficial for both fundamental-science and industrial applications. Without greater partnership, leadership, and strategic planning with industry, the NNSA is risking increased competition for the top-caliber workforce and decreased capability to meet the technology needs for the future.

  • Recommendation
    The NNSA should collaboratively develop industry-relevant technical roadmaps for critical capabilities in computation, diagnostics, and targets and provide more—and more frequent—funding opportunities for industry to provide these capabilities.

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Essential Investments for the Workforce

In order to ensure a robust HED science workforce, appropriate investment and support is needed from an early stage to ensure diversity and build a broad and engaged community.

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An overarching challenge that NNSA faces is retention and recruitment of the expert workforce that carries out HED science. The exploding influence of the private sector, developments in other nations, and challenges to the workplace climate put at risk the approach and laboratories in HED research that have served the nation well since World War II.

Therefore, it is of crucial importance to broaden the number of sources for HED science candidates, as well as the number of career pathways one might take into HED science. The committee makes this the focus of its second leading recommendation:

LEADING RECOMMENDATION
To enhance career pathways for high energy density science research at NNSA facilities, the NNSA should

  1. broaden its current programs for achieving excellence through diversity, equity, and inclusion while improving workplace climate and
  2. develop a strategic plan for balancing security and proliferation concerns with openness and accessibility, such as for collaborators internationally, and with academia and the private sector.

VIEW RELATED RECOMMENDATIONS

Below is a list of recommendations the committee believes will help address current issues faced by the HEDS workforce.

  • Recommendation
    The NNSA should take steps to enable institutions working on high energy density research to (1) assess the [workplace] climate; (2) get help from subject-matter experts to make explicit and quantifiable diversity, equity, inclusion, and accessibility (DEIA) goals; and (3) implement and ensure achievement of these DEIA goals.
  • Recommendation
    The NNSA should support more internships, postdoctoral opportunities, faculty visitorships, and early career programs in high energy density science, coordinating across the NNSA in a manner similar to that supported by the Department of Energy’s Office of Science.
  • Recommendation
    The NNSA should provide explicit support and recognition for national laboratory scientists to increase collaborations, mentorship, and outreach with the fundamental research community, in order to build public excitement and the future workforce. Examples include joint appointments or sabbatical opportunities and travel/lectureship programs that partner with minority-serving institutions and the public at large.
  • Recommendation
    The NNSA should periodically assess and, where possible, reduce barriers to university collaborations—for example, by formally recognizing the importance of, and therefore supporting and rewarding, laboratory staff engaged in effective collaborations.
  • Recommendation
    NNSA laboratories should enforce concrete policies for accountability around intolerable, unacceptable behaviors.
  • Recommendation
    In addition to training Ph.D. scientists, NNSA laboratories should invest in educational (apprenticeship) programs at institutions for training of technicians and technical staff at the bachelor’s or master’s level, doing so in line with the laboratories’ diversity, equity, inclusion, and accessibility goals.
  • Recommendation
    NNSA national laboratories should promote collaborations with academia by sharing data related to unclassified research (in consistent data format) and providing open/educational versions of their computational codes.

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International Collaboration and Workforce

HED science is a collaborative field in nature and maintaining strong national and international collaborations facilitates retaining and recruiting a global workforce.

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While the United States is a leader in traditional HED science with high energy lasers and pulsed power Z-pinches, changes are occurring that could alter that situation. Materials science under extreme pressure can now also be studied at smaller facilities, and the current and planned high-intensity lasers in Europe and Asia far exceed the power of those in the U.S. 

International collaborations strengthen collaborations within the HED science workforce, and thus enhance the utilization of HED science facilities. Increased usage of these facilities remotely (i.e., with remote access) would also enhance their utilization by both domestic and international users.

The nation will also need to find ways to attract domestic students and retain international students in relevant domains of science and technology, and to work out solutions allowing those students trained in the U.S. to remain in the country.

VIEW RELATED RECOMMENDATIONS

  • Recommendation
    To strengthen its global leadership in high energy density science and address future national needs, the NNSA should increase the promotion of forefront technology development, and in particular take the necessary steps to achieve ultra-high power laser capabilities on par with what is being developed around the world.
  • Recommendation
    To enhance career pathways for high energy density science research at NNSA facilities, the NNSA should promote international collaborations and increase remote access to those facilities.

Learn more about Essential International Collaboration and Workforce

Frequently Asked Questions

The National Defense Authorization Act for Fiscal Year 2020, Congress directed the National Nuclear Security Administration to sponsor this study, specifying an emphasis on basic science.

HED science is a wide-ranging, rapidly evolving research frontier seeking to understand and control material at extreme conditions. (For example, the domain of HED science is defined by pressures exceeding one million times atmospheric pressure.) Materials under these conditions exhibit properties not observed in our everyday environment: nonmetals become metals, crystals take on surprisingly complex structures, and normal mass can be converted into energy. Experts from several other fields—such as astrophysics, condensed-matter and plasma physics, materials chemistry, high-pressure research, and planetary science—join together to address topics ranging from security to sustainability.

Selection of appropriate committee members is essential for the success of a study. One of the strengths of the National Academies is the tradition of bringing together recognized experts across many disciplines and facilitating collaboration. Careful steps are taken to convene diverse committees that have an appropriate range of expertise and represent a balance of perspectives. Stakeholders will have the opportunity to nominate potential committee members at the beginning of the study, and all nominations are carefully considered. Provisional committee members are screened for possible conflicts of interest. All committee members serve as individual experts, not as representatives of organizations or interest groups.

The final report of the study will be directed at policy makers, industry, NGOs, the public, and the scientific community. These groups, including the U.S. Congress and the executive branch, will be briefed on the key messages of the report. The committee and Academies staff will also work to communicate the report’s findings to stakeholders and non-specialist audiences.

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PHOTO CREDITS:
Key Discoveries (Fusion): LLNL; Key Discoveries (Chemistry): S.X. Hu, V.V. Karasiev, V. Recoules, P.M. Nilson, N. Brouwer, and M. Torrent, 2020, “Interspecies Radiative Transition in Warm and Superdense Plasma Mixtures,” Nature Communications 11:1989; CC BY 4.0.; Key Discoveries (Un-Metallization): Reprinted by permission from Springer Nature: Y. Ma, M. Eremets, A. Oganov, et al., 2009, “Transparent Dense Sodium,” Nature 458:182-185; © 2009; Astrophysical Jet: NASA/CXC/SAO (x-ray image), NASA/STScI (visible light image), NSF/NRAO/AUI/VLA (radio waves image); Science Investments: LLNL