Tagged: PPPL Toggle Comment Threads | Keyboard Shortcuts

  • richardmitnick 2:42 pm on November 11, 2020 Permalink | Reply
    Tags: "Advancing the arrival of fusion energy through improved understanding of fast plasma particles", , , , PPPL   

    From DOE’s PPPL: “Advancing the arrival of fusion energy through improved understanding of fast plasma particles” 


    From PPPL

    November 11, 2020
    John Greenwald

    1
    Physicist Laura Xin Zhang with figures from her paper. Credit: Elle Starkman/Office of Communications.

    Unlocking the zig-zagging dance of hot, charged plasma particles that fuel fusion reactions can help to harness on Earth the fusion energy that powers the sun and stars. At the U.S. Department of Energy’s (DOE) Princeton Plasma Physics Laboratory (PPPL), an experimentalist and two theorists have developed a new algorithm, or set of computer rules, for tracking volatile particles that could advance the arrival of safe, clean and virtually limitless source of energy.

    Close interaction

    “This is a success story about close interaction between theorists and experimentalists that shows what can be done,” said Hong Qin, a principal theoretical physicist at PPPL. He and Yichen Fu, a theoretical graduate student whom he advises, collaborated on the algorithm with Laura Xin Zhang, an experimental graduate student and lead author of a paper Physical Review E that reports the research in the journal Physical Review E. Qin and Fu coauthored the paper.

    Fusion powers the sun and stars by combining light elements in the form of plasma — the state of matter composed of free electrons and atomic nuclei, or ions, that makes up 99 percent of the visible universe — to release massive amounts of energy. Scientists around the world are seeking to produce controlled fusion on Earth as an ideal source for generating electricity.

    The new PPPL algorithm helps track fast charged particles in the plasma. The particles could, for example, stem from the injection of high-energy neutral beams that are broken down, or “ionized” in the plasma and collide with the main plasma particles. “We care about this because we want to understand how these fast particles influence the plasma,” Zhang said.

    Neutral beams play many roles when broken down into fast plasma particles. “We use them to do all sorts of things,” Zhang said. “They can heat and drive current in the plasma. Sometimes they create plasma instabilities and sometimes they reduce them. Our simulations are all part of understanding how these particles behave.”

    First a problem

    When Zhang first tried simulating the fast particles she ran into a problem. She used a classic algorithm that failed to conserve energy during what is called the pitch-angle scattering process of particles colliding. Such scattering is often observed in fusion plasma when electrons collide with ions that are roughly 2,000-times heavier in collisions akin to ping-pong balls bouncing off basketballs.

    For Zhang, the problem “was similar to trying to simulate the orbit of a planet,” she recalled. Just as the energy of an orbit does not change, “you want an algorithm that conserves the energy of the scattered plasma particles,” she said.

    Conserving that energy is critical, said Qin, whom Zhang consulted. “If an algorithm that simulates the process does not conserve the energy of the particles, the simulation cannot be trusted,” he said. He thus devised an alternative method, an explicitly solvable algorithm that conserves the energy of the particles, which Zhang went on to try.

    ” I’m an experimentalist at heart and my approach to problems is to try it,” she said. “So I ran a bunch of simulations and did all kinds of numerical experiments that showed the algorithm worked better than the classic algorithm that failed to conserve energy.” However, the alternative method could not be proven theoretically.

    Qin next handed the problem to graduate student Fu, who put together a clever mathematical proof of the correctness of the algorithm that could become a step to further solutions. “The algorithm we developed is for a simplified model,” Zhang said. “It drops several terms that will be important to include. But I am charging ahead and aiming to apply the algorithm we’ve developed to new plasma physics problems.”

    Support for this work comes from the DOE Office of Science.

    See the full article here .


    five-ways-keep-your-child-safe-school-shootings
    Please help promote STEM in your local schools.

    Stem Education Coalition


    PPPL campus

    Princeton Plasma Physics Laboratory is a U.S. Department of Energy national laboratory managed by Princeton University. PPPL, on Princeton University’s Forrestal Campus in Plainsboro, N.J., is devoted to creating new knowledge about the physics of plasmas — ultra-hot, charged gases — and to developing practical solutions for the creation of fusion energy. Results of PPPL research have ranged from a portable nuclear materials detector for anti-terrorist use to universally employed computer codes for analyzing and predicting the outcome of fusion experiments. The Laboratory is managed by the University for the U.S. Department of Energy’s Office of Science, which is the largest single supporter of basic research in the physical sciences in the United States, and is working to address some of the most pressing challenges of our time. For more information, please visit https://energy.gov/science.

    About Princeton: Overview
    Princeton University is a vibrant community of scholarship and learning that stands in the nation’s service and in the service of all nations. Chartered in 1746, Princeton is the fourth-oldest college in the United States. Princeton is an independent, coeducational, nondenominational institution that provides undergraduate and graduate instruction in the humanities, social sciences, natural sciences and engineering.

    As a world-renowned research university, Princeton seeks to achieve the highest levels of distinction in the discovery and transmission of knowledge and understanding. At the same time, Princeton is distinctive among research universities in its commitment to undergraduate teaching.

    Today, more than 1,100 faculty members instruct approximately 5,200 undergraduate students and 2,600 graduate students. The University’s generous financial aid program ensures that talented students from all economic backgrounds can afford a Princeton education.

    Princeton Shield

     
  • richardmitnick 2:28 pm on November 3, 2020 Permalink | Reply
    Tags: "Building a star in a smaller jar", , Improved confinement is made possible by the so-called enhanced pedestal (EP) H-mode., Plasma in fusion technology, PPPL,   

    From PPPL: “Building a star in a smaller jar” 


    From PPPL

    October 29, 2020
    Raphael Rosen

    1
    PPPL physicist Devon Battaglia with graphs illustrating fusion plasma in enhanced pedestal H-mode. Credit: Elle Starkman.

    PPPL NSTX-U Tokamak.

    Researchers at the U.S. Department of Energy’s (DOE) Princeton Plasma Physics Laboratory (PPPL) have gained a better understanding of a promising method for improving the confinement of superhot fusion plasma using magnetic fields. Improved plasma confinement could enable a fusion reactor called a spherical tokamak to be built smaller and less expensively, moving the world closer to reproducing on Earth the fusion energy that powers the sun and stars.

    The improved confinement is made possible by the so-called enhanced pedestal (EP) H-mode, a variety of the high performance, or H-mode, plasma state that has been observed for decades in tokamaks around the world. When a fusion plasma enters H-mode, it requires less heating to get to the superhot temperatures necessary for fusion reactions.

    The new understanding reveals some of the underlying mechanics of EP H-mode, a condition that researchers discovered more than a decade ago. Scientists led by physicists at PPPL have now found that the EP H-mode improves upon H-mode in spherical tokamaks by lowering the density of the plasma edge.

    The reduced density occurs in EP H-mode when small instabilities in the plasma edge eject relatively cold, low-energy particles. With fewer cold particles to bump into, the hotter particles in the plasma are less likely to leak out.

    “As the higher energy particles stay in the plasma in larger quantities, they increase the pressure in the plasma, feeding the instabilities that throw out colder particles and further lowering the edge density,” said PPPL physicist Devon Battaglia, lead author of a paper reporting the results in Physics of Plasmas. “Ultimately, the fortuitous interaction allows the plasma to stay hotter with the same heating and little change to the average plasma density.”

    Physicists want to understand the conditions under which EP H-mode occurs so they can recreate them in future fusion power plants. “If we could run the plasma with this characteristic in a steady-state fashion, it would provide an additional route to optimize the size and power gain of future fusion reactors,” said PPPL physicist Walter Guttenfelder, one of the researchers who contributed to the findings.

    Fusion reactors combine light elements in the form of plasma — the hot, charged state of matter composed of free electrons and atomic nuclei — to generate large amounts of energy. Scientists use fusion reactors to develop the process that drives the sun and stars for a virtually inexhaustible supply of power to generate electricity.

    Physicists Rajesh Maingi and David Gates discovered EP H-mode in 2009 while using PPPL’s National Spherical Torus Experiment (NSTX), the predecessor of the National Spherical Torus Experiment-Upgrade (NSTX-U). “Their discovery was exciting because the confined plasma reorganized and did a better job of holding on to its heat without a big change in the amount of plasma,” said Battaglia.

    “It’s like adding better insulation to your house,” he said. “The more the plasma holds on to its heat, the smaller you can make the device, since you don’t need additional layers of plasma to insulate the hot core.” Moreover, he added, “by taking a leap in our understanding of how EP H-mode comes about, we can have more confidence in being able to predict if it’s going to happen. The next step is to use the new capabilities of NSTX-U to demonstrate that we can take advantage of this process in our designs for fusion reactors.”

    Collaborators have included researchers from PPPL and the University of Wisconsin-Madison. The research was supported by the DOE’s Office of Science.

    NSTX-U is a DOE Office of Science user facility.

    See the full article here .


    five-ways-keep-your-child-safe-school-shootings
    Please help promote STEM in your local schools.

    Stem Education Coalition


    PPPL campus

    Princeton Plasma Physics Laboratory is a U.S. Department of Energy national laboratory managed by Princeton University. PPPL, on Princeton University’s Forrestal Campus in Plainsboro, N.J., is devoted to creating new knowledge about the physics of plasmas — ultra-hot, charged gases — and to developing practical solutions for the creation of fusion energy. Results of PPPL research have ranged from a portable nuclear materials detector for anti-terrorist use to universally employed computer codes for analyzing and predicting the outcome of fusion experiments. The Laboratory is managed by the University for the U.S. Department of Energy’s Office of Science, which is the largest single supporter of basic research in the physical sciences in the United States, and is working to address some of the most pressing challenges of our time. For more information, please visit https://energy.gov/science.

    About Princeton: Overview
    Princeton University is a vibrant community of scholarship and learning that stands in the nation’s service and in the service of all nations. Chartered in 1746, Princeton is the fourth-oldest college in the United States. Princeton is an independent, coeducational, nondenominational institution that provides undergraduate and graduate instruction in the humanities, social sciences, natural sciences and engineering.

    As a world-renowned research university, Princeton seeks to achieve the highest levels of distinction in the discovery and transmission of knowledge and understanding. At the same time, Princeton is distinctive among research universities in its commitment to undergraduate teaching.

    Today, more than 1,100 faculty members instruct approximately 5,200 undergraduate students and 2,600 graduate students. The University’s generous financial aid program ensures that talented students from all economic backgrounds can afford a Princeton education.

    Princeton Shield

     
  • richardmitnick 9:51 am on October 24, 2020 Permalink | Reply
    Tags: "Exploring the source of stars and planets in a laboratory", , , , PPPL   

    From PPPL: “Exploring the source of stars and planets in a laboratory” 


    From PPPL

    October 23, 2020
    John Greenwald

    1
    Physicist Himawan Winarto with figures from paper behind him.Credit: Elle Starkman/Office of Communications.

    A new method for verifying a widely held but unproven theoretical explanation of the formation of stars and planets has been proposed by researchers at the U.S. Department of Energy’s (DOE) Princeton Plasma Physics Laboratory (PPPL). The method grows from simulation of the Princeton Magnetorotational Instability (MRI) Experiment, a unique laboratory device that aims to demonstrate the MRI process that is believed to have filled the cosmos with celestial bodies.

    Cosmic dust

    The novel device, designed to duplicate the process that causes swirling clouds of cosmic dust and plasma to collapse into stars and planets, consists of two fluid-filled concentric cylinders that rotate at different speeds. The device seeks to replicate the instabilities that are thought to cause the swirling clouds to gradually shed what is called their angular momentum and collapse into the growing bodies that they orbit. Such momentum keeps the Earth and other planets firmly within their orbits.

    “In our simulations we can actually see the MRI develop in experiments,” said Himawan Winarto, a graduate student in the Princeton Program in Plasma Physics at PPPL and lead author of a paper in Physical Review E that reports the findings. “We also are proposing a new diagnostic system to measure MRI,” said Winarto, whose interest in the subject began as an intern in the University of Tokyo-Princeton University Partnership on Plasma Physics while an undergraduate at Princeton University.

    The suggested system would measure the strength of the radial, or circular, magnetic field that the rotating inner cylinder generates in experiments. Since the strength of the field correlates strongly with expected turbulent instabilities, the measurements could help pinpoint the source of the turbulence.

    “Our overall objective is to show the world that we’ve unambiguously seen the MRI effect in the lab,” said physicist Erik Gilson, one of Himawan’s mentors on the project and a coauthor of the paper. “What Himawan is proposing is a new way to look at our measurements to get at the essence of MRI.”

    Surprising results

    The simulations have shown some surprising results. While MRI is normally observable only at a sufficiently high rate of cylinder rotation, the new findings indicate that instabilities can likely be seen well before the upper limit of the experimental rotation rate is reached. “That means speeds much closer to the rates we are running now,” Winarto said, “and projects to the rotational speed that we should aim for to see MRI.”

    A key challenge to spotting the source of MRI is the existence of other effects that can act like MRI but are not in fact the process. Prominent among these deceptive effects are what are called Rayleigh instabilities that break up fluids into smaller packets, and Ekman circulation that alters the profile of fluid flow. The new simulations clearly indicate “that MRI, rather than Ekman circulation or Rayleigh instability, dominates the fluid behavior in the region where MRI is expected,” Winarto said.

    The findings thus shed new light on the growth of stars and planets that populate the universe. “Simulations are very useful to point you in the right direction to help interpret some of the diagnostic results of experiments,” Gilson said. “What we see from these results is that the signals for MRI look like they should be able to be seen more easily in experiments than we had previously thought.”

    Funding for this work comes from the U.S. Department of Energy Office of Science; NASA; and the Max- Planck-Princeton Center for Plasma Physics. Collaborators include PPPL physicists Fatima Ebrahimi and Yin Wang; Hantao Ji, a PPPL physicist and professor of astrophysical sciences at Princeton University; and Jeremy Goodman, professor of astrophysical sciences at Princeton University. Jean-Luc Guermond of Texas A&M University provided the SFEMaNS simulation code used extensively in the paper.

    See the full article here .


    five-ways-keep-your-child-safe-school-shootings
    Please help promote STEM in your local schools.

    Stem Education Coalition


    PPPL campus

    Princeton Plasma Physics Laboratory is a U.S. Department of Energy national laboratory managed by Princeton University. PPPL, on Princeton University’s Forrestal Campus in Plainsboro, N.J., is devoted to creating new knowledge about the physics of plasmas — ultra-hot, charged gases — and to developing practical solutions for the creation of fusion energy. Results of PPPL research have ranged from a portable nuclear materials detector for anti-terrorist use to universally employed computer codes for analyzing and predicting the outcome of fusion experiments. The Laboratory is managed by the University for the U.S. Department of Energy’s Office of Science, which is the largest single supporter of basic research in the physical sciences in the United States, and is working to address some of the most pressing challenges of our time. For more information, please visit https://energy.gov/science.

    Princeton University campus

     
  • richardmitnick 8:43 am on September 5, 2020 Permalink | Reply
    Tags: "Researchers find unexpected electrical current that could stabilize fusion reactions", , PPPL   

    From PPPL: “Researchers find unexpected electrical current that could stabilize fusion reactions” 


    From PPPL

    September 4, 2020
    Raphael Rosen

    1
    An artist’s rendering of electrical current flowing through a tokamak fusion facility. (Photo by Elle Starkman.)

    Electric current is everywhere, from powering homes to controlling the plasma that fuels fusion reactions to possibly giving rise to vast cosmic magnetic fields. Now, scientists at the U.S. Department of Energy’s (DOE) Princeton Plasma Physics Laboratory (PPPL) have found that electrical currents can form in ways not known before. The novel findings could give researchers greater ability to bring the fusion energy that drives the sun and stars to Earth.

    “It’s very important to understand which processes produce electrical currents in plasma and which phenomena could interfere with them,” said Ian Ochs, graduate student in Princeton University’s Program in Plasma Physics and lead author of a paper selected as a featured article in Physics of Plasmas. “They are the primary tool we use to control plasma in magnetic fusion research.”

    Fusion is the process that smashes together light elements in the form of plasma — the hot, charged state of matter composed of free electrons and atomic nuclei — generating massive amounts of energy. Scientists are seeking to replicate fusion for a virtually inexhaustible supply of power to generate electricity.

    The unexpected currents arise in the plasma within doughnut-shaped fusion facilities known as tokamaks.

    PPPL NSTX -U tokamak at Princeton Plasma Physics Lab, Princeton, NJ,USA.

    The currents develop when a particular type of electromagnetic wave, such as those that radios and microwave ovens emit, forms spontaneously. These waves push some of the already-moving electrons, “which ride the wave like surfers on a surfboard,” said Ochs.

    But the frequencies of these waves matter. When the frequency is high, the wave causes some electrons to move forward and others backward. The two motions cancel each other out and no current occurs.

    However, when the frequency is low, the waves pushes forward on the electrons and backward on the atomic nuclei, or ions, creating a net electrical current after all. Ochs found that researchers could surprisingly create these currents when the low-frequency wave was a particular type called an “ion acoustic wave” that resembles sound waves in air.

    The significance of this finding extends from the relatively small scale of the laboratory to the vast scale of the cosmos. “There are magnetic fields throughout the universe on different scales, including the size of galaxies, and we don’t really know how they got there,” Ochs said. “The mechanism we discovered could have helped seed cosmic magnetic fields, and any new mechanisms that can produce magnetic fields are interesting to the astrophysics community.”

    The results from the pencil-and-paper calculations consist of mathematical expressions that give scientists the ability to calculate how these currents, which occur without electrons directly interacting, develop and grow. “The formulation of these expressions was not straightforward,” Ochs said. “We had to condense the findings so they would be sufficiently clear and use simple expressions to capture the key physics.”

    The results deepen understanding of a basic physical phenomenon and were also unexpected. They appear to contradict the conventional notion that current drives require electron collisions, Ochs said.

    “The question of whether waves can drive any current in plasma is actually very deep and goes to the fundamental interactions of waves in plasma,” said Nathaniel Fisch, a coauthor of the paper, professor and associate chair of the Department of Astrophysical Sciences, and director of the Program in Plasma Physics. “What Ochs derived in masterful, didactic fashion, with mathematical rigor, was not only how these effects are sometimes balanced, but also how these effects sometimes conspire to allow the formation of net electrical currents.”

    These findings lay the groundwork for future research. “What especially excites me,” Fisch said, “is that the mathematical formalism that Ochs has built, together with the physical intuitions and insights that he has acquired, now put him in a position either to challenge or to put on a firm foundation even more curious behavior in the interactions of waves with resonant particles in plasma.”

    See the full article here .


    five-ways-keep-your-child-safe-school-shootings
    Please help promote STEM in your local schools.

    Stem Education Coalition


    PPPL campus

    Princeton Plasma Physics Laboratory is a U.S. Department of Energy national laboratory managed by Princeton University. PPPL, on Princeton University’s Forrestal Campus in Plainsboro, N.J., is devoted to creating new knowledge about the physics of plasmas — ultra-hot, charged gases — and to developing practical solutions for the creation of fusion energy. Results of PPPL research have ranged from a portable nuclear materials detector for anti-terrorist use to universally employed computer codes for analyzing and predicting the outcome of fusion experiments. The Laboratory is managed by the University for the U.S. Department of Energy’s Office of Science, which is the largest single supporter of basic research in the physical sciences in the United States, and is working to address some of the most pressing challenges of our time. For more information, please visit https://energy.gov/science.

    Princeton University campus

     
  • richardmitnick 2:41 pm on June 25, 2020 Permalink | Reply
    Tags: "Scientists develop new tool to design better fusion devices", , PPPL,   

    From PPPL: “Scientists develop new tool to design better fusion devices” 


    From PPPL

    June 24, 2020
    Raphael Rosen

    One way that scientists seek to bring to Earth the fusion process that powers the sun and stars is trapping hot, charged plasma gas within a twisting magnetic coil device shaped like a breakfast cruller. But the device, called a stellarator, must be precisely engineered to prevent heat from escaping the plasma core where it stokes the fusion reactions.

    Wendelstgein 7-X stellarator, built in Greifswald, Germany

    Now, researchers at the U.S. Department of Energy’s (DOE) Princeton Plasma Physics Laboratory (PPPL) have demonstrated that an advanced computer code could help design stellarators that confine the essential heat more effectively.

    The code, called XGC-S, opens new doors in stellarator research. “The main result of our research is that we can use the code to simulate both the early, or linear, and turbulent plasma behavior in stellarators,” said PPPL physicist Michael Cole, lead author of the paper reporting the results in Physics of Plasmas. “This means that we can start to determine which stellarator shape contains heat best and most efficiently maintains conditions for fusion.”

    Fusion combines light elements in the form of plasma — the hot, charged state of matter composed of free electrons and atomic nuclei — and generates massive amounts of energy in the sun and stars. Scientists aim to replicate fusion in devices on Earth for a virtually inexhaustible supply of safe and clean power to generate electricity.

    The PPPL scientists simulated the behavior of plasma inside fusion machines that look like a donut but with pinches and deformations that make the device more efficient, a kind of shape known as quasi-axisymmetric . The researchers used an updated version of XGC, a state-of-the-art code developed at PPPL for modeling turbulence in doughnut-shaped fusion facilities called tokamaks, which have a simpler geometry. The modifications by Cole and his colleagues allowed the new XGC-S code to also model plasmas in the geometrically more complicated stellarators.

    The simulations showed that a type of disturbance limited to a small area can become complex and expand to fill a larger space within the plasma. The results showed that XGC-S could simulate this type of stellarator plasma more accurately than what was previously possible.

    “I think this is the beginning of a really important development in the study of turbulence in stellarators,” said David Gates, head of the Department of Advanced Projects at PPPL. “It opens up a big window for getting new results.”

    The findings demonstrate the successful modification of the XGC code to simulate turbulence in stellarators. The code can calculate the turbulence in stellarators all the way from the plasma core to the edge, providing a more complete picture of the plasma’s behavior.

    “Turbulence is one of the primary mechanisms causing heat to leak out of fusion plasmas,” Cole said. “Because stellarators can be built in a greater variety of shapes than tokamaks, we might be able to find shapes that control turbulence better than tokamaks do. Searching for them by building lots of big experiments is too expensive, so we need big simulations to search for them virtually.”

    The researchers plan to modify XGC-S further to produce an even clearer view of how turbulence causes heat leakage. The more complete a picture, the closer scientists will be to simulating stellarator experiments in the virtual realm. “Once you have an accurate code and a powerful computer, changing the stellarator design you are simulating is easy,” Cole said.

    Researchers performed the simulations using resources at the National Energy Research Scientific Computing Center (NERSC), a DOE User Facility. Support for this research came from the DOE Office of Science (Fusion Energy Sciences).

    See the full article here .


    five-ways-keep-your-child-safe-school-shootings
    Please help promote STEM in your local schools.

    Stem Education Coalition


    PPPL campus

    Princeton Plasma Physics Laboratory is a U.S. Department of Energy national laboratory managed by Princeton University. PPPL, on Princeton University’s Forrestal Campus in Plainsboro, N.J., is devoted to creating new knowledge about the physics of plasmas — ultra-hot, charged gases — and to developing practical solutions for the creation of fusion energy. Results of PPPL research have ranged from a portable nuclear materials detector for anti-terrorist use to universally employed computer codes for analyzing and predicting the outcome of fusion experiments. The Laboratory is managed by the University for the U.S. Department of Energy’s Office of Science, which is the largest single supporter of basic research in the physical sciences in the United States, and is working to address some of the most pressing challenges of our time. For more information, please visit science.http://www.energy.gov.

    Princeton University campus

     
  • richardmitnick 10:33 am on May 27, 2020 Permalink | Reply
    Tags: "Return of the Blob: Scientists find surprising link to troublesome turbulence at the edge of fusion plasmas", Blobs can wreak havoc in plasma required for fusion reactions., , , PPPL   

    From PPPL: “Return of the Blob: Scientists find surprising link to troublesome turbulence at the edge of fusion plasmas” 


    From PPPL

    May 26, 2020
    John Greenwald

    1
    Image showing spiraling magnetic field fluctuations at the edge of the NSTX tokamak. (Photo courtesy of Physics of Plasmas. Composition by Elle Starkman/Office of Communications.)

    PPPL NSTX -U at Princeton Plasma Physics Lab, Princeton, NJ,USA

    Blobs can wreak havoc in plasma required for fusion reactions. This bubble-like turbulence swells up at the edge of fusion plasmas and drains heat from the edge, limiting the efficiency of fusion reactions in doughnut-shaped fusion facilities called “tokamaks.” Researchers at the U.S. Department of Energy’s (DOE) Princeton Plasma Physics Laboratory (PPPL) have now discovered a surprising correlation of the blobs with fluctuations of the magnetic field that confines the plasma fueling fusion reactions in the device core.

    New aspect of understanding

    Further investigation of this correlation and its role in the loss of heat from magnetic fusion reactors will help to produce on Earth the fusion energy that powers the sun and stars. “These results add a new aspect to our understanding of the plasma edge heat loss in a tokamak,” said physicist Stewart Zweben, lead author of a paper (link is external) in Physics of Plasmas that editors have selected as a featured article. “This work also contributes to our understanding of the physics of blobs, which can help to predict the performance of tokamak fusion reactors.”

    Fusion reactions combine light elements in the form of plasma — the hot, charged state of matter composed of free electrons and atomic nuclei that makes up 99 percent of the visible universe — to produce massive amounts of energy. Scientists are seeking to create and control fusion on Earth as a source of safe, clean and virtually limitless power to generate electricity.

    PPPL researchers discovered the surprising link last year when re-analyzing experiments made in 2010 on PPPL’s National Spherical Torus Experiment (NSTX) — the forerunner of today’s National Spherical Torus Experiment-Upgrade (NSTX-U). The blobs and fluctuations in the magnetic field, called “magnetohydrodynamic (MHD)” activity, develop in all tokamaks and have traditionally been seen as independent of each other.

    Surprise clue

    The first clue to the correlation was the striking regularity of the trajectory of large blobs, which travel at roughly the speed of a rifle bullet, in experiments analyzed in 2015 and 2016. Such blobs normally move randomly in what is called the “scrape-off layer” at the edge of tokamak plasma, but in some cases all large blobstraveled at nearly the same angle and speed. Moreover, the time between the appearance of each large blob at the edge of the plasma was nearly always the same, virtually coinciding with the frequency of dominant MHD activity in the plasma edge.

    Researchers then tracked the diagnostic signals of the blobs and the MHD activity in relation to each other to measure what is called the “cross-correlation coefficient,” which they used to evaluate a set of the 2010 NSTX experiments. Roughly 10 percent of those experiments were found to show a significant correlation between the two variables.

    The scientists then analyzed several possible causes of the correlation, but could find no single compelling explanation. To understand and control this phenomenon, Zweben said, further data analysis and modeling will have to be done — perhaps by readers of the Physics of Plasmas paper.

    Support for this work comes from the DOE Office of Science, with portions of the research performed under the auspices of Lawrence Livermore National Laboratory.

    See the full article here .


    five-ways-keep-your-child-safe-school-shootings
    Please help promote STEM in your local schools.

    Stem Education Coalition


    PPPL campus

    Princeton Plasma Physics Laboratory is a U.S. Department of Energy national laboratory managed by Princeton University. PPPL, on Princeton University’s Forrestal Campus in Plainsboro, N.J., is devoted to creating new knowledge about the physics of plasmas — ultra-hot, charged gases — and to developing practical solutions for the creation of fusion energy. Results of PPPL research have ranged from a portable nuclear materials detector for anti-terrorist use to universally employed computer codes for analyzing and predicting the outcome of fusion experiments. The Laboratory is managed by the University for the U.S. Department of Energy’s Office of Science, which is the largest single supporter of basic research in the physical sciences in the United States, and is working to address some of the most pressing challenges of our time. For more information, please visit science.http://www.energy.gov.

    Princeton University campus

     
  • richardmitnick 2:26 pm on April 16, 2020 Permalink | Reply
    Tags: "Applying mathematics to accelerate predictions for capturing fusion energy", PPPL   

    From PPPL: “Applying mathematics to accelerate predictions for capturing fusion energy” 


    From PPPL

    April 14, 2020
    John Greenwald

    1
    Physicist Ben Sturdevant with figures from paper. (Photo and composite by Elle Starkman/PPPL Office of Communications.)

    A key issue for scientists seeking to bring the fusion that powers the sun and stars to Earth is forecasting the performance of the volatile plasma that fuels fusion reactions. Making such predictions calls for considerable costly time on the world’s fastest supercomputers. Now researchers at the U.S. Department of Energy’s (DOE) Princeton Plasma Physics Laboratory (PPPL) have borrowed a technique from applied mathematics to accelerate the process.

    The technique combines the millisecond behavior of fusion plasmas into longer-term forecasts. By using it, “we were able to demonstrate that accurate predictions of quantities such as plasma temperature profiles and heat fluxes could be achieved at a much reduced computational cost,” said Ben Sturdevant, an applied mathematician at PPPL and lead author of a Physics of Plasmas paper that reported the results.

    Fusion combines light elements in the form of plasma — the hot, charged state of matter composed of free electrons and atomic nuclei — that generates massive amounts of energy. Scientists are working around the world to create and control fusion on Earth for a virtually inexhaustible supply of safe and clean power to generate electricity.

    Speeding simulations

    Sturdevant applied the mathematical technique to the high-performance XGCa plasma code developed by a team led by physicist C.S. Chang at PPPL. The application greatly speeded up simulations of the evolving temperature profile of ions orbiting around magnetic field lines modeled with gyrokinetics — a widely used model that provides a detailed microscopic description of the behavior of plasma in strong magnetic fields. Also accelerated was modeling the collisions between orbiting particles that cause heat to leak from the plasma and reduce its performance.

    The application was the first successful use of the technique, called “equation-free projective integration,” to model the evolution of the ion temperature as colliding particles escape from magnetic confinement. Equation free modeling aims to extract long-term macroscopic information from short-term microscopic simulations. The key was improving a critical aspect of the technique called a “lifting operator” to map the large-scale, or macroscopic, states of plasma behavior onto small-scale, or microscopic, ones.

    The modification brought the detailed profile of the ion temperature into sharp relief. “Rather than directly simulating the evolution over a long time-scale, this method uses a number of millisecond simulations to make predictions over a longer time-scale,” Sturdevant said. “The improved process reduced the computing time by a factor of four.”

    The results, based on tokamak simulations, are general and could be adapted for other magnetic fusion devices including stellarators and even for other scientific applications. “This is an important step in being able to confidently predict performance in fusion energy devices from first-principles-based physics,” Sturdevant said.

    Expanding the technique

    He next plans to consider the effect of expanding the technique to include the evolution of turbulence on the speed of the process. “Some of these initial results are promising and exciting,” Sturdevant said. “We’re very interested to see how it will work with the inclusion of turbulence.”

    Coauthors of the paper include Chang, PPPL physicist Robert Hager and physicist Scott Parker of the University of Colorado. Chang and Parker were advisors, Sturdevant said, while Hager provided help with the XGCa code and the computational analysis.

    Support for this work comes from the Exascale Computing Project, a collaborative effort of the DOE Office of Science and the National Nuclear Security Administration, and Scientific Discovery through Advanced Computing (SciDAC). Computer simulations were performed at the National Energy Research Scientific Computing Center (NERSC), a DOE Office of Science User Facility.

    2

    See the full article here .


    five-ways-keep-your-child-safe-school-shootings
    Please help promote STEM in your local schools.

    Stem Education Coalition


    PPPL campus

    Princeton Plasma Physics Laboratory is a U.S. Department of Energy national laboratory managed by Princeton University. PPPL, on Princeton University’s Forrestal Campus in Plainsboro, N.J., is devoted to creating new knowledge about the physics of plasmas — ultra-hot, charged gases — and to developing practical solutions for the creation of fusion energy. Results of PPPL research have ranged from a portable nuclear materials detector for anti-terrorist use to universally employed computer codes for analyzing and predicting the outcome of fusion experiments. The Laboratory is managed by the University for the U.S. Department of Energy’s Office of Science, which is the largest single supporter of basic research in the physical sciences in the United States, and is working to address some of the most pressing challenges of our time. For more information, please visit science.http://www.energy.gov.

    Princeton University campus

     
  • richardmitnick 1:06 pm on February 13, 2020 Permalink | Reply
    Tags: "Investigating the trigger for a sudden explosive process that occurs throughout the universe", Lundquist number, PPPL   

    From PPPL and Princeton University : “Investigating the trigger for a sudden explosive process that occurs throughout the universe” 

    Princeton University
    From Princeton University

    and

    From PPPL

    February 12, 2020
    John Greenwald

    1
    Physicist Yi-Min Huang. (Photo by Elle Starkman/Office of Communications)

    A long-standing puzzle in space science is what triggers fast magnetic reconnection, an explosive process that unfolds throughout the universe more rapidly than theory says it should.

    NASA Magnetic reconnection, Credit: M. Aschwanden et al. (LMSAL), TRACE, NASA

    Solving the puzzle could enable scientists to better understand and anticipate the process, which ignites solar flares and magnetic space storms that can disrupt cell phone service and black out power grids on Earth.

    Magnetic reconnection separates and violently reconnects the magnetic fields in plasma, the state of matter composed of free electrons and atomic nuclei that make up 99 percent of the visible universe. Researchers at the U.S. Department of Energy’s (DOE) Princeton Plasma Physics Laboratory (PPPL) and Princeton University have recently produced a formula for tracking the development of “plasmoid-instability-mediated disruptions,” which trigger the transition from slow to fast reconnection.

    The research traces the dependence of the instability on conditions ranging from the electrical conductivity of the plasma — measured by what is called the Lundquist number — to the natural noise of the system. “You give me the Lundquist number and system noise and I can fit it into the formula that will spit out the answer,” said physicist Yi-Min Huang, a Princeton University member of the PPPL Theory Department and lead author of a paper describing the process in Physics of Plasmas.

    Tracking the evolution of “plasmoids”

    The calculation tracks the evolution of plasmoids, bubbles that form in current-carrying sheets of plasma. When the bubbles are large enough, they trigger disruptions that cause fast reconnection. “We are interested in finding out when the plasmoids will disrupt the current sheet and the number of plasmoids when disruptions happen,” Huang said.

    The formula for relating the factors that lead to disruptions is based on a complex “phenomenological” model — one deduced from a combination of physical reasoning and mathematical derivation. “As a general rule,” Huang said, “a phenomenological model must be tested through numerical simulations” against first-principle, or standard, physics models.

    The versatile new formula tracks the dependence of disruptions on a broad range of high Lundquist numbers. Derived results can be compared with simulations of laboratory experiments and used to describe the development of plasmoid instabilities in natural systems.
    Previously, the dependence could only be obtained by solving the equations of the complex model, Huang said.

    Co-authors of the Physics of Plasmas paper were Luca Comisso of Columbia University and Amitava Bhattacharjee, head of PPPL’s Theory Department. Support for the research comes from the National Science Foundation, the DOE Office of Science and the National Aeronautics and Space Administration.

    See the full article here .


    five-ways-keep-your-child-safe-school-shootings
    Please help promote STEM in your local schools.

    Stem Education Coalition

    About Princeton: Overview

    Princeton University is a vibrant community of scholarship and learning that stands in the nation’s service and in the service of all nations. Chartered in 1746, Princeton is the fourth-oldest college in the United States. Princeton is an independent, coeducational, nondenominational institution that provides undergraduate and graduate instruction in the humanities, social sciences, natural sciences and engineering.

    As a world-renowned research university, Princeton seeks to achieve the highest levels of distinction in the discovery and transmission of knowledge and understanding. At the same time, Princeton is distinctive among research universities in its commitment to undergraduate teaching.

    Today, more than 1,100 faculty members instruct approximately 5,200 undergraduate students and 2,600 graduate students. The University’s generous financial aid program ensures that talented students from all economic backgrounds can afford a Princeton education.

    Princeton Shield


    PPPL campus

    Princeton Plasma Physics Laboratory is a U.S. Department of Energy national laboratory managed by Princeton University. PPPL, on Princeton University’s Forrestal Campus in Plainsboro, N.J., is devoted to creating new knowledge about the physics of plasmas — ultra-hot, charged gases — and to developing practical solutions for the creation of fusion energy. Results of PPPL research have ranged from a portable nuclear materials detector for anti-terrorist use to universally employed computer codes for analyzing and predicting the outcome of fusion experiments. The Laboratory is managed by the University for the U.S. Department of Energy’s Office of Science, which is the largest single supporter of basic research in the physical sciences in the United States, and is working to address some of the most pressing challenges of our time. For more information, please visit science.http://www.energy.gov.

    Princeton University campus

     
  • richardmitnick 3:37 pm on November 13, 2019 Permalink | Reply
    Tags: A goal of instilling entrepreneurship, , , Funding for research liaisons, , PPPL, PPPL wins DOE funding for entrepreneurship"   

    From PPPL: “PPPL wins DOE funding for entrepreneurship” 

    From PPPL

    November 13, 2019
    Jeanne Jackson DeVoe

    1
    Craig Arnold, a professor of Aerospace Engineering at Princeton University, and founder of TAG Optics Inc., discusses his experiences starting a business at the Jan. 23 Entrepreneurship Lunch and Learn in the MBG Auditorium. (Photo by Elle Starkman/PPPL Office of Communications)

    The U.S. Department of Energy’s (DOE) Princeton Plasma Physics Laboratory (PPPL) will expand an entrepreneurship “lunch and learn” program pioneered at PPPL last year and appoint mentors to help and encourage potential entrepreneurs in the Laboratory through two U.S. Department of Energy (DOE) projects totaling $70,000 awarded to PPPL’s Technology Transfer Office.

    PPPL will participate in three and receive funding for two of 12 projects through DOE’s Practices to Accelerate the Commercialization of Technologies (PACT) program developed by DOE’s Office of Technology Transition (OTT) to help promote the transition of inventions developed at the 17 national laboratories and plants to the marketplace.

    “I’m thrilled that PPPL received these awards,” said Laurie Bagley, head of Technology Transfer. “We are delighted to have the funding to provide support and training to our entrepreneurs, as well as to provide mentorship and training in collaboration with other laboratories.

    A goal of instilling entrepreneurship

    Steve Cowley, laboratory director, said he is glad to see funding for programs that encourage PPPL inventors. He noted that the DOE set a goal of instilling a culture of entrepreneurship as a “notable” requirement for all national laboratory directors in fiscal years 2019 and 2020. “One of PPPL’s major goals is to develop useful new technologies of all kinds,” Cowley said. “Laurie has done a wonderful job in developing programs to encourage entrepreneurship and these awards are a reflection of that. I hope everyone on our staff will take advantage of these programs and learn how to bring out their inner inventors.”

    PPPL received $40,000 from the DOE’s Office of Technology Transitions to continue and expand the Entrepreneurship Lunch and Learn program begun last year by Bagley, to offer information and support to current and future entrepreneurs at the Laboratory. The additional funds will allow PPPL to bring in a wider variety of experts on a range of topics affecting entrepreneurs, Bagley said. Topics could include how to identify ideal customers, developing marketing leads and plans, intellectual property’s role in a start-up, and entrepreneur success stories. The talks could also help improve the skill set of inventors presenting their technologies at events such as the Innovation Discovery Events, technology showcases or Energy I-Corps programs, Bagley said.

    This award is aimed at encouraging entrepreneurship throughout PPPL’s staff, not just physicists and engineers. “The goal is to get people here thinking more entrepreneurially, so if they are working on a technology that can be patented or have an idea to start a business, they’ll have a deeper understanding to make those decisions,” Bagley said.

    PPPL’s Office of Technology Transfer offered four such talks last year to audience members and ranged from advice from a Princeton University entrepreneur on the challenges of starting a business to services available to entrepreneurs through Princeton University and the DOE’s Office of Technology Transition’s Program.

    Funding for research liaisons

    The Laboratory will also participate in a $30,000 project through a new pilot initiative, the DOE Technology Transfer Research Liaison Program. The program was championed by Oak Ridge National Laboratory (ORNL) as a collaborative effort with 11 national laboratories, including PPPL. The idea is to strengthen the relationship between the lab’s tech transfer office and its researchers and engineers to identify inventors and encourage and advise them about how to develop technologies, some of which can eventually be brought to market. PPPL will select three liaisons, who will receive training along with liaisons at other laboratories. The liaisons will then serve as champions and mentors by offering help and encouragement on questions about invention disclosures, patents, and other technology transfer issues.

    In addition to the awards, PPPL was named as one of 11 partners in another new DOE program, Diversity and Inclusion in InVentorship and EntrepReneurship Strategies and Engagement (DIVERSE), which is aimed at encouraging a more diverse pool of inventors and entrepreneurs.

    See the full article here .


    five-ways-keep-your-child-safe-school-shootings
    Please help promote STEM in your local schools.

    Stem Education Coalition


    PPPL campus

    Princeton Plasma Physics Laboratory is a U.S. Department of Energy national laboratory managed by Princeton University. PPPL, on Princeton University’s Forrestal Campus in Plainsboro, N.J., is devoted to creating new knowledge about the physics of plasmas — ultra-hot, charged gases — and to developing practical solutions for the creation of fusion energy. Results of PPPL research have ranged from a portable nuclear materials detector for anti-terrorist use to universally employed computer codes for analyzing and predicting the outcome of fusion experiments. The Laboratory is managed by the University for the U.S. Department of Energy’s Office of Science, which is the largest single supporter of basic research in the physical sciences in the United States, and is working to address some of the most pressing challenges of our time. For more information, please visit science.http://www.energy.gov.

    Princeton University campus

     
  • richardmitnick 1:06 pm on September 20, 2019 Permalink | Reply
    Tags: "How to predict crucial plasma pressure in future fusion facilities", Accurate predictions of the pressure of the plasma, , , , PPPL   

    From PPPL- “Today’s forecast: How to predict crucial plasma pressure in future fusion facilities” 

    From PPPL

    September 20, 2019
    John Greenwald

    1
    Physicist Michael Churchill. (Photo by Elle Starkman/Office of Communications)

    A key requirement for future facilities that aim to capture and control on Earth the fusion energy that drives the sun and stars is accurate predictions of the pressure of the plasma — the hot, charged gas that fuels fusion reactions inside doughnut-shaped tokamaks that house the reactions. Central to these predictions is forecasting the pressure that the scrape-off layer, the thin strip of gas at the edge of the plasma, exerts on the divertor — the device that exhausts waste heat from fusion reactions.

    Researchers at the U.S. Department of Energy’s (DOE) Princeton Plasma Physics Laboratory (PPPL) have developed new insights into the physics governing the balance of pressure in the scrape-off layer. This balance must ensure that the pressure of the plasma throughout the tokamak is high enough to produce a largely self-heating fusion reaction. The balance must also limit the potentially damaging impact of heat and plasma particles that strike the divertor and other plasma-facing components of the tokamak.

    “Previous simple assumptions about the balance of pressure in the scrape-off layer are incomplete,” said PPPL physicist Michael Churchill, lead author of a Nuclear Fusion paper that describes the new findings. “The codes that simulate the scrape-off layer have often thrown away important aspects of the physics, and the field is starting to recognize this.”

    Fusion, the power that drives the sun and stars, is the fusing of light elements in the form of plasma — the hot, charged state of matter composed of free electrons and atomic nuclei — that generates massive amounts of energy. Scientists are seeking to replicate fusion on Earth for a virtually inexhaustible supply of power to generate electricity.

    Key factors

    Churchill and PPPL colleagues determined the key factors behind the pressure balance by running the state-of-the-art XGCa computer code on the Cori and Edison supercomputers at the National Energy Research Scientific Computing Center (NERSC), a DOE Office of Science User Facility.

    NERSC at LBNL

    NERSC Cray Cori II supercomputer, named after Gerty Cori, the first American woman to win a Nobel Prize in science

    NERSC Hopper Cray XE6 supercomputer, named after Grace Hopper, One of the first programmers of the Harvard Mark I computer

    NERSC Cray XC30 Edison supercomputer

    NERSC GPFS for Life Sciences


    The Genepool system is a cluster dedicated to the DOE Joint Genome Institute’s computing needs. Denovo is a smaller test system for Genepool that is primarily used by NERSC staff to test new system configurations and software.

    NERSC PDSF computer cluster in 2003.

    PDSF is a networked distributed computing cluster designed primarily to meet the detector simulation and data analysis requirements of physics, astrophysics and nuclear science collaborations.

    Future:

    Cray Shasta Perlmutter SC18 AMD Epyc Nvidia pre-exascale supeercomputer

    NERSC is a DOE Office of Science User Facility.

    The code treats plasma at a detailed kinetic — or particle motion— level rather than as a fluid.

    Among key features found was the impact of the bulk drift of ions, an impact that previous codes have largely ignored. Such drifts “can play an integral role” the authors wrote, and “are very important to take into account.”

    Also seen to be important in the momentum or pressure balance were the kinetic particle effects due to ions having different temperatures depending on their direction. Since the temperature of ions is hard to measure in the scrape-off layer, the paper says, “increased diagnostic efforts should be made to accurately measure the ion temperature and flows and thus enable a better understanding of the role of ions in the SOL.”

    The new findings could improve understanding of the scrape-off layer pressure at the divertor, Churchill said, and could lead to accurate forecasts for the international ITER experiment under construction in France and other next-generation tokamaks.

    ITER Tokamak in Saint-Paul-lès-Durance, which is in southern France

    Support for this work comes from the DOE Office of Science under the SciDAC Center for High Fidelity Boundary Plasma Simulation (HBPS). The research used resources of the National Energy Research Scientific Computing Center (NERSC). Coauthors of the paper were PPPL physicists C.S Chang, Seung-Ho Ku, Robert Hager, Rajesh Maingi, Daren Stotler and Hong Qin.

    See the full article here .


    five-ways-keep-your-child-safe-school-shootings
    Please help promote STEM in your local schools.

    Stem Education Coalition


    PPPL campus

    Princeton Plasma Physics Laboratory is a U.S. Department of Energy national laboratory managed by Princeton University. PPPL, on Princeton University’s Forrestal Campus in Plainsboro, N.J., is devoted to creating new knowledge about the physics of plasmas — ultra-hot, charged gases — and to developing practical solutions for the creation of fusion energy. Results of PPPL research have ranged from a portable nuclear materials detector for anti-terrorist use to universally employed computer codes for analyzing and predicting the outcome of fusion experiments. The Laboratory is managed by the University for the U.S. Department of Energy’s Office of Science, which is the largest single supporter of basic research in the physical sciences in the United States, and is working to address some of the most pressing challenges of our time. For more information, please visit science.http://www.energy.gov.

    Princeton University campus

     
c
Compose new post
j
Next post/Next comment
k
Previous post/Previous comment
r
Reply
e
Edit
o
Show/Hide comments
t
Go to top
l
Go to login
h
Show/Hide help
shift + esc
Cancel
%d bloggers like this: