DOE News
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    The DOE Science News Source is a Newswise initiative to promote research news from the Office of Science of the DOE to the public and news media.
    • 2018-12-12 15:05:38
    • Article ID: 705074

    Drawn into a Whirlpool: A New Way to Stop Dangerous Fast Electrons in a Fusion Device

    A new phenomena forms vortices that trap particles, impeding electron avalanches that harm fusion reactors.

    The Science

    As the density, temperature, and currents in the hot ionized gas, known as plasma, inside experimental fusion devices reach the point where hydrogen ions fuse to form helium and huge amounts of energy are released, the electric currents become increasingly difficult to control. If control is lost, the plasma disrupts. A dangerous avalanche of fast electrons is continuously accelerated by a self-generated electric field. These electrons can escape and melt “hot spots” in the wall. In addition to avoidance strategies, the scientists that operate future fusion reactors need mitigation strategies to reduce the damage. A new approach exploits a fan instability first observed in electromagnetic waves in the Earth’s atmosphere.

    The Impact

    Because of this fan instability, the fast electron beam moves chaotically as it passes through the background plasma, just as water flowing through a flexible hose causes it to move as a snake does. This process excites a “whistler wave” in which the frequency drops from high to low, just like a slide whistle. Scientists have found whistler waves in both Earth’s radiation belt (thanks to NASA’s Van Allen Probes) and in the DIII-D National Fusion Facility. In a big step forward for using whistler waves in mitigation strategies, scientists have accurately simulated their interaction with electron beams both theoretically and numerically using advanced computational models.

    Summary

    Just like when pushing a playground swing, energy is only transferred from the electron beam to the whistler wave when the “pushing” and “swinging” are at the same frequency (that is, in resonance). But in tokamaks (fusion devices that contain the plasma), the electron rotation frequency is much larger than that of the whistler wave. So how can there be a resonant energy transfer that diffuses electron energy?

    The continuous acceleration of the electrons means they get faster and faster until their speed approaches the speed of light. Then, Einstein’s theory of relativity kicks in. The mass of the electrons increases, time seems to slow down, and the resonance condition changes.

    To better understand this process, scientists at the Princeton Plasma Physics Laboratory have developed a numerical simulation code that fully utilizes modern multi-core processors. When the resonance condition is satisfied, the electrons are drawn away from their original trajectories and trapped inside whirlpool-like vortices formed by the whistler waves. The energy is diffused and the momentum scattered; this is exactly what is required for mitigation: impede the relativistic electrons before they hit the wall.

    Simulations of existing experiments show the importance of this fan instability in the suppression of avalanches and the enhancement of radiation (that is, cooling) from the runaway electrons. Scientists are now testing this idea as a mitigation strategy in ITER, where the whistler waves are either caused by self-excited fan instability or by the use of external antennas, to limit the damage caused by disruptions.

    Funding

    This work was supported by the Department of Energy, Office of Science, Fusion Energy Sciences.

    Publications

    C. Liu, E. Hirvijoki, G.Y. Fu, D.P. Brennan, A. Bhattacharjee, and C. Paz-Soldan, “Role of kinetic instability in runaway-electron avalanches and elevated critical electric fields.” Physical Review Letter 120, 265001 (2018). [DOI: 10.1103/PhysRevLett.120.265001]

    C. Liu, L. Shi, E. Hirvijoki, D.P. Brennan, A. Bhattacharjee, C. Paz-Soldan, and M.E. Austin, “The effects of kinetic instabilities on the electron cyclotron emission from runaway electrons.” Nuclear Fusion 58, 096030 (2018). [DOI: 10.1088/1741-4326/aacc9b]

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    Microbes Retain Toxicity Tolerance After They Escape Toxic Elements

    Microbes Retain Toxicity Tolerance After They Escape Toxic Elements

    Ground water microbes living outside a contaminated area contain mobile genetic elements that provide them resistance to heavy metals.

    Practice makes perfect

    Practice makes perfect

    Argonne researchers are beginning to employ Bayesian methods in developing optimal models of thermodynamic properties. Research available online for the September 2019 issue of the International Journal of Engineering Science focused on hafnium (Hf), a metal emerging as a key component in computer electronics.

    Science Snapshots: A toxin antidote in frogs, atomic motion in 4D, and better biofuels

    Science Snapshots: A toxin antidote in frogs, atomic motion in 4D, and better biofuels

    In new work by Berkeley Lab and our collaborators, scientists discover how a protein made by bullfrogs inhibits the deadly neurotoxin involved in red tide events, perform the first observation of how atoms arrange in four dimensions during phase transitions, and describe a new bacterial gene that could be engineered into biofuel-producing bacteria to significantly boost efficiency.

    Trees Consider the Climate When Choosing Their Partners

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    ees can establish several types of symbiotic relationships with fungi and bacteria. Researchers constructed a global map of the types of tree symbioses across the world. With the map, they determined that the type of fungal symbiosis found in trees depends on how quickly the organic matter in the soil decomposes. The team also found that bacteria that convert nitrogen gas from the atmosphere into plant-usable products form tree symbioses in arid environments.

    First Snapshots of Trapped CO2 Molecules Shed New Light on Carbon Capture

    First Snapshots of Trapped CO2 Molecules Shed New Light on Carbon Capture

    Scientists from the Department of Energy's SLAC National Accelerator Laboratory and Stanford University have taken the first images of carbon dioxide molecules within a molecular cage (break)(break)- part of a highly porous nanoparticle known as a MOF, or metal-organic framework, with great potential for separating and storing gases and liquids.

    New Geometric Model Improves Predictions of Fluid Flow in Rock

    New Geometric Model Improves Predictions of Fluid Flow in Rock

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    Feeding Sugars to Algae Makes Them Fat

    Feeding Sugars to Algae Makes Them Fat

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    Scientists show how one cause of weak enamel unfolds on the molecular level

    Scientists show how one cause of weak enamel unfolds on the molecular level

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    Explaining Light-Nuclei Production in Heavy-Ion Nuclear Collisions

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    Scientists hit pay dirt with new microbial research technique

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    Long ago, during the European Renaissance, Leonardo da Vinci wrote that we humans "know more about the movement of celestial bodies than about the soil underfoot." Five hundred years and innumerable technological and scientific advances later, his sentiment still holds true. But that could soon change. A new study in Nature Communications details how an improved method for studying microbes in the soil will help scientists understand both fine-grained details and large-scale cycles of the environment.


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    Department of Energy Announces $13 Million for Atmospheric Research

    The U.S. Department of Energy (DOE) announced $13 million in funding for 27 projects in atmospheric sciences in an effort to improve models for predicting weather and climate.

    John Crane acquires division of Advanced Diamond Technologies, a company built on Argonne technology

    John Crane acquires division of Advanced Diamond Technologies, a company built on Argonne technology

    John Crane, a global provider of engineered products and services headquartered in Chicago, recently completed the purchase of Advanced Diamond Technologies (ADT), Industrial Division. ADT was founded in 2003 through the licensing of technology from the U.S. Department of Energy's (DOE's) Argonne National Laboratory.

    Energy Department to Invest $32 Million in Computer Design of Materials

    The U.S. Department of Energy announced that it will invest $32 million over the next four years to accelerate the design of new materials through use of supercomputers.

    Demarteau to head ORNL Physics Division

    Demarteau to head ORNL Physics Division

    The Department of Energy's Oak Ridge National Laboratory has named Marcel Demarteau as Physics Division Director, effective June 17.

    PPPL and Oak Ridge manage new DOE program designed to speed development of fusion energy with private-public partnerships

    PPPL and Oak Ridge manage new DOE program designed to speed development of fusion energy with private-public partnerships

    Feature describes PPPL role in innovative DOE program to promote public-private partnerships to speed development of fusion energy.

    ORNL welcomes seven new research fellows to Innovation Crossroads

    ORNL welcomes seven new research fellows to Innovation Crossroads

    Oak Ridge National Laboratory welcomed seven technology innovators to join the third cohort of Innovation Crossroads, the Southeast's only entrepreneurial research and development program based at a U.S. Department of Energy national laboratory.

    New DOE program connects fusion companies with national labs, taps ORNL to lead

    New DOE program connects fusion companies with national labs, taps ORNL to lead

    The Department of Energy has established the Innovation Network for Fusion Energy program, or INFUSE, to encourage private-public research partnerships for overcoming challenges in fusion energy development.

    Department of Energy Announces $75 Million for High Energy Physics Research

    The U.S. Department of Energy (DOE) announced $75 million in funding for 66 university research awards on a range of topics in high energy physics to advance knowledge of how the universe works at its most fundamental level.

    Ames Laboratory names James Morris Chief Research Officer

    Ames Laboratory names James Morris Chief Research Officer

    Dr. James Morris has been named Chief Research Officer at the Department of Energy's (DOE) Ames Laboratory. His appointment follows an extensive search and will be effective June 17, 2019.

    Four scientists at PPPL awarded national and international honors

    Four scientists at PPPL awarded national and international honors

    Feature profiles four PPPL scientists who have received high honors.


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    Deep Learning Reveals Mysteries of Deep Space

    Deep Learning Reveals Mysteries of Deep Space

    How do you determine the measurable "things" that describe the nature of our universe? To answer that question, researchers used CosmoFlow, a deep learning technique, running on a National Energy Research Scientific Computing Center supercomputer. They analyzed large, complex data sets from 3-D simulations of the distribution of matter to answer that question. The team showed that CosmoFlow offers a new platform to gain a deeper understanding of the universe.

    At DOE's Manufacturing Demonstration Facility, science drives next-gen creations

    At DOE's Manufacturing Demonstration Facility, science drives next-gen creations

    American ingenuity is providing radical productivity improvements from advanced materials and robotic systems developed at the Department of Energy's Manufacturing Demonstration Facility at Oak Ridge National Laboratory.

    High-Fidelity Multiphysics Simulations to Improve Nuclear Reactor Safety and Economics

    High-Fidelity Multiphysics Simulations to Improve Nuclear Reactor Safety and Economics

    Engineers can model heat distribution in reactor designs with fewer or no approximations.

    Tiny Vortices Could One Day Haul Microscopic Cargo

    Tiny Vortices Could One Day Haul Microscopic Cargo

    The behavior of active magnetic liquids suggests new pathways to transport particles across surfaces and build materials that self-heal.

    How Does Mother Nature Tackle the Tough Triple Bond Found in Nitrogen?

    How Does Mother Nature Tackle the Tough Triple Bond Found in Nitrogen?

    Researchers demystify how the nitrogenase enzyme breaks bonds to learn a better way to make ammonia.

    A Detailed View of the Ancestor of Photosynthesis

    A Detailed View of the Ancestor of Photosynthesis

    The symmetrical light-gathering, energy-producing complex offers insights into how modern photosystems evolved.

    Unique Interface and Unexpected Behavior Help Explain How Heavy Metals Act

    Unique Interface and Unexpected Behavior Help Explain How Heavy Metals Act

    Three types of water molecules form around a platinum-based ion, offering insights for waste processing and metal refining.

    Maximizing Ozone Signals

    Maximizing Ozone Signals

    New technique enables more efficient and precise estimates of trends in ozone and other atmospheric constituents within selected geographical regions and timeframes.

    How Much Water Does the World Use?

    How Much Water Does the World Use?

    Global data set shows monthly water use by irrigation, manufacturing, and other uses, helping researchers to analyze water use by region and season.

    Get to the Root: Tiny Poplar Roots Extract More Water than Their Larger Counterparts after Drought

    Get to the Root: Tiny Poplar Roots Extract More Water than Their Larger Counterparts after Drought

    Researchers link root water uptake to root traits and assess (poor) performance of common models.


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