Tagged: Fusion technology Toggle Comment Threads | Keyboard Shortcuts

  • richardmitnick 7:14 am on December 3, 2016 Permalink | Reply
    Tags: , Fusion technology, , ,   

    From PPPL: “PPPL and Max Planck physicists confirm the precision of magnetic fields in the most advanced stellarator in the world” 


    PPPL

    December 2, 2016
    John Greenwald

    Physicist Sam Lazerson of the U.S. Department of Energy’s (DOE) Princeton Plasma Physics Laboratory (PPPL) has teamed with German scientists to confirm that the Wendelstein 7-X (W7-X) fusion energy device called a stellarator in Greifswald, Germany, produces high-quality magnetic fields that are consistent with their complex design.

    PPPL Wendelstein 7-X, built in Greifswald, Germany
    Wendelstein 7-X, built in Greifswald, Germany

    The findings, published in the November 30 issue of Nature Communications, revealed an error field — or deviation from the designed configuration — of less than one part in 100,000. Such results could become a key step toward verifying the feasibility of stellarators as models for future fusion reactors.

    W7-X, for which PPPL is the leading U.S. collaborator, is the largest and most sophisticated stellarator in the world. Built by the Max Planck Institute for Plasma Physics in Greifswald, it was completed in 2015 as the vanguard of the stellarator design. Other collaborators on the U.S. team include DOE’s Oak Ridge and Los Alamos National Laboratories, along with Auburn University, the Massachusetts Institute of Technology, the University of Wisconsin-Madison and Xanthos Technologies.

    Twisty magnetic fields

    Stellarators confine the hot, charged gas, otherwise known as plasma, that fuels fusion reactions in twisty — or 3D — magnetic fields, compared with the symmetrical — or 2D –fields that the more widely used tokamaks create.

    PPPL NSTXII
    PPPL NSTX

    The twisty configuration enables stellarators to control the plasma with no need for the current that tokamaks must induce in the gas to complete the magnetic field. Stellarator plasmas thus run little risk of disrupting, as can happen in tokamaks, causing the internal current to abruptly halt and fusion reactions to shut down.

    PPPL has played key roles in the W7-X project. The Laboratory designed and delivered five barn door-sized trim coils that fine-tune the stellarator’s magnetic fields and made their measurement possible. “We’ve confirmed that the magnetic cage that we’ve built works as designed,” said Lazerson, who led roughly half the experiments that validated the configuration of the field. “This reflects U.S. contributions to W7-X,” he added, “and highlights PPPL’s ability to conduct international collaborations.” Support for this work comes from Euratom and the DOE Office of Science.

    To measure the magnetic field, the scientists launched an electron beam along the field lines. They next obtained a cross-section of the entire magnetic surface by using a fluorescent rod to intersect and sweep through the lines, thereby inducing fluorescent light in the shape of the surface.

    Remarkable fidelity

    Results showed a remarkable fidelity to the design of the highly complex magnetic field. “To our knowledge,” the authors write of the discrepancy of less than one part in 100,000, “this is an unprecedented accuracy, both in terms of the as-built engineering of a fusion device, as well as in the measurement of magnetic topology.”

    The W7-X is the most recent version of the stellarator concept, which Lyman Spitzer, a Princeton University astrophysicist and founder of PPPL, originated during the 1950s. Stellarators mostly gave way to tokamaks a decade later, since the doughnut-shaped facilities are simpler to design and build and generally confine plasma better. But recent advances in plasma theory and computational power have led to renewed interest in stellarators.

    Such advances caused the authors to wonder if devices like the W7-X can provide an answer to the question of whether stellarators are the right concept for fusion energy. Years of plasma physics research will be needed to find out, they conclude, and “that task has just started.”

    See the full article here .

    Please help promote STEM in your local schools.

    STEM Icon

    Stem Education Coalition

    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.energy.gov.

     
  • richardmitnick 10:42 am on November 30, 2016 Permalink | Reply
    Tags: , Fusion technology, , ,   

    From The Conversation: “Fusion energy: A time of transition and potential” 

    Conversation
    The Conversation

    November 29, 2016
    Stewart Prager
    Professor of Astrophysical Science, former director of the Princeton Plasma Physics Laboratory, Princeton University

    Michael C. Zarnstorff
    Deputy Director for Research, Princeton Plasma Physics Laboratory, Princeton University

    1
    fusion energy. murrayashmole

    For centuries, humans have dreamed of harnessing the power of the sun to energize our lives here on Earth. But we want to go beyond collecting solar energy, and one day generate our own from a mini-sun. If we’re able to solve an extremely complex set of scientific and engineering problems, fusion energy promises a green, safe, unlimited source of energy. From just one kilogram of deuterium extracted from water per day could come enough electricity to power hundreds of thousands of homes.

    Since the 1950s, scientific and engineering research has generated enormous progress toward forcing hydrogen atoms to fuse together in a self-sustaining reaction – as well as a small but demonstrable amount of fusion energy. Skeptics and proponents alike note the two most important remaining challenges: maintaining the reactions over long periods of time and devising a material structure to harness the fusion power for electricity.

    As fusion researchers at the Princeton Plasma Physics Lab, we know that realistically, the first commercial fusion power plant is still at least 25 years away.

    PPPLII

    But the potential for its outsize benefits to arrive in the second half of this century means we must keep working. Major demonstrations of fusion’s feasibility can be accomplished earlier – and must, so that fusion power can be incorporated into planning for our energy future.

    Unlike other forms of electrical generation, such as solar, natural gas and nuclear fission, fusion cannot be developed in miniature and then be simply scaled up. The experimental steps are large and take time to build. But the problem of abundant, clean energy will be a major calling for humankind for the next century and beyond. It would be foolhardy not to exploit fully this most promising of energy sources.

    Why fusion power?

    2
    Adding heat to two isotopes of water can result in fusion. American Security Project, CC BY-ND

    In fusion, two nuclei of the hydrogen atom (deuterium and tritium isotopes) fuse together. This is relatively difficult to do: Both nuclei are positively charged, and therefore repel each other. Only if they are moving extremely fast when they collide will they smash together, fuse and thereby release the energy we’re after.

    This happens naturally in the sun. Here on Earth, we use powerful magnets to contain an extremely hot gas of electrically charged deuterium and tritium nuclei and electrons. This hot, charged gas is called a plasma.

    The plasma is so hot – more than 100 million degrees Celsius – that the positively charged nuclei move fast enough to overcome their electrical repulsion and fuse. When the nuclei fuse, they form two energetic particles – an alpha particle (the nucleus of the helium atom) and a neutron.

    Heating the plasma to such a high temperature takes a large amount of energy – which must be put into the reactor before fusion can begin. But once it gets going, fusion has the potential to generate enough energy to maintain its own heat, allowing us to draw off excess heat to turn into usable electricity.

    Fuel for fusion power is abundant in nature. Deuterium is plentiful in water, and the reactor itself can make tritium from lithium. And it is available to all nations, mostly independent of local natural resources.

    Fusion power is clean. It emits no greenhouse gases, and produces only helium and a neutron.

    It is safe. There is no possibility for a runaway reaction, like a nuclear-fission “meltdown.” Rather, if there is any malfunction, the plasma cools, and the fusion reactions cease.

    All these attributes have motivated research for decades, and have become even more attractive over time. But the positives are matched by the significant scientific challenge of fusion.

    Progress to date

    The progress in fusion can be measured in two ways. The first is the tremendous advance in basic understanding of high-temperature plasmas. Scientists had to develop a new field of physics – plasma physics – to conceive of methods to confine the plasma in strong magnetic fields, and then evolve the abilities to heat, stabilize, control turbulence in and measure the properties of the superhot plasma.

    Related technology has also progressed enormously. We have pushed the frontiers in magnets, and electromagnetic wave sources and particle beams to contain and heat the plasma. We have also developed techniques so that materials can withstand the intense heat of the plasma in current experiments.

    It is easy to convey the practical metrics that track fusion’s march to commercialization. Chief among them is the fusion power that has been generated in the laboratory: Fusion power generation escalated from milliwatts for microseconds in the 1970s to 10 megawatts of fusion power (at the Princeton Plasma Physics Laboratory) and 16 megawatts for one second (at the Joint European Torus in England) in the 1990s.

    PPPL NSTX
    PPPL NSTX

    A new chapter in research

    4
    Under construction: the ITER research tokamak in France. ITER

    ITER Tokamak
    ITER Tokamak

    Now the international scientific community is working in unity to construct a massive fusion research facility in France. Called ITER (Latin for “the way”), this plant will generate about 500 megawatts of thermal fusion power for about eight minutes at a time. If this power were converted to electricity, it could power about 150,000 homes. As an experiment, it will allow us to test key science and engineering issues in preparation for fusion power plants that will function continuously.

    ITER employs the design known as the “tokamak,” originally a Russian acronym. It involves a doughnut-shaped plasma, confined in a very strong magnetic field, which is partly created by electrical current that flows in the plasma itself.

    Though it is designed as a research project, and not intended to be a net producer of electric energy, ITER will produce 10 times more fusion energy than the 50 megawatts needed to heat the plasma. This is a huge scientific step, creating the first “burning plasma,” in which most of the energy used to heat the plasma comes from the fusion reaction itself.

    ITER is supported by governments representing half the world’s population: China, the European Union, India, Japan, Russia, South Korea and the U.S. It is a strong international statement about the need for, and promise of, fusion energy.

    The road forward

    From here, the remaining path toward fusion power has two components. First, we must continue research on the tokamak. This means advancing physics and engineering so that we can sustain the plasma in a steady state for months at a time. We will need to develop materials that can withstand an amount of heat equal to one-fifth the heat flux on the surface of the sun for long periods. And we must develop materials that will blanket the reactor core to absorb the neutrons and breed tritium.

    The second component on the path to fusion is to develop ideas that enhance fusion’s attractiveness. Four such ideas are:

    5
    The W-7X stellarator configuration. Max-Planck Institute of Plasmaphysics, CC BY

    Wendelstgein 7-X stellarator
    Wendelstgein 7-X stellarator

    1) Using computers, optimize fusion reactor designs within the constraints of physics and engineering. Beyond what humans can calculate, these optimized designs produce twisted doughnut shapes that are highly stable and can operate automatically for months on end. They are called “stellarators” in the fusion business.

    2) Developing new high-temperature superconducting magnets that can be stronger and smaller than today’s best. That will allow us to build smaller, and likely cheaper, fusion reactors.

    3) Using liquid metal, rather than a solid, as the material surrounding the plasma. Liquid metals do not break, offering a possible solution to the immense challenge how a surrounding material might behave when it contacts the plasma.

    4) Building systems that contain doughnut-shaped plasmas with no hole in the center, forming a plasma shaped almost like a sphere. Some of these approaches could also function with a weaker magnetic field. These “compact tori” and “low-field” approaches also offer the possibility of reduced size and cost.

    Government-sponsored research programs around the world are at work on the elements of both components – and will result in findings that benefit all approaches to fusion energy (as well as our understanding of plasmas in the cosmos and industry). In the past 10 to 15 years, privately funded companies have also joined the effort, particularly in search of compact tori and low-field breakthroughs. Progress is coming and it will bring abundant, clean, safe energy with it.

    See the full article here .

    Please help promote STEM in your local schools.

    STEM Icon

    Stem Education Coalition

    The Conversation US launched as a pilot project in October 2014. It is an independent source of news and views from the academic and research community, delivered direct to the public.
    Our team of professional editors work with university and research institute experts to unlock their knowledge for use by the wider public.
    Access to independent, high quality, authenticated, explanatory journalism underpins a functioning democracy. Our aim is to promote better understanding of current affairs and complex issues. And hopefully allow for a better quality of public discourse and conversation.

     
  • richardmitnick 12:57 pm on November 25, 2016 Permalink | Reply
    Tags: China Experimental Advanced Superconducting Tokamak, Chinese Researchers Contain Energy of an 'Artificial Sun', Fusion technology,   

    From INVERSE: “Chinese Researchers Contain Energy of an ‘Artificial Sun’ “ 

    INVERSE

    INVERSE

    November 10, 2016
    Tonya Riley

    1

    In February, Chinese researchers met a milestone by creating a nuclear reactor plasma that reached a temperature of 50 million Kelvins (50 million degrees Celsius), which was three times the heat produced by the sun’s core. Now, they’re reporting that they’ve managed to actually contain the energy the reactor produces for an entire minute, bringing them closer to a fully functional “artificial sun” and future of sustainable thermonuclear energy.

    2

    The experiment was conducted using the Experimental Advanced Superconducting Tokamak
    , an experimental thermonuclear reactor at the Institute of Plasma Physics at the Chinese Academy of Sciences. The reactor, which was completed in 2006, replicates the energy of the sun through creating a plasma, a hot ionized gas where atoms fuse together to create large amounts of energy. This is different from nuclear energy created by fission, which a reaction causes atoms to divide rather than merge.

    In September, China General Nuclear Power Group (CGN) won a bid to take over 9 percent of ITER’s nuclear power research. Details of the agreement, including a budget and a supplement agreement for the design of a steam-condensing tank, were finalized in November.

    ITER, which comprises China, the European Union, India, Japan, Korea, Russia, and the United States as members, was launched as an international joint experiment in fusion in 1985. According to its website, the coalition aims to “prove the feasibility of fusion as a large-scale and carbon-free source of energy based on the same principle that powers the sun.” Ultimately, ITER wants to create a reactor that can produce 500 megawatts of fusion output for 400 seconds. While Chinese researchers did not reveal the exact length of the most recent test, they say it was longer than 102 seconds, the record set in February.

    4
    ITER tokamak

    The United States initially committed to building roughly 9 percent of the ITER project and, as of 2016, has spent $3.9 billion on it on research for tests that won’t occur until 2020 at the earliest. In 2015, researchers at MIT announced a design for a new nuclear fusion reactor that is able to produce a magnetic field strong enough to contain large amounts of plasma in a relatively tiny fusion reactor.

    Private companies have also become major players in the fusion energy game. California-based companies General Fusion and Tri Alpha Energy have attracted nearly half a billion each in venture funding. With China’s latest advancement, however, ITER could still be on track to reach its 2035 deadline.

    See the full article here .

    Please help promote STEM in your local schools.

    STEM Icon

    Stem Education Coalition

     
  • richardmitnick 2:31 pm on November 23, 2016 Permalink | Reply
    Tags: Fusion technology, , , ,   

    From Princeton: “An explanation for the mysterious onset of a universal process (Physics of Plasmas)” 

    Princeton University
    Princeton University


    PPPL

    November 23, 2016
    John Greenwald, Princeton Plasma Physics Laboratory Communications

    1
    Magnetic reconnection happens in solar flares on the surface in the sun, as well as in experimental fusion energy reactors here on Earth. Image credit: NASA.

    Scientists have proposed a groundbreaking solution to a mystery that has puzzled physicists for decades. At issue is how magnetic reconnection, a universal process that sets off solar flares, northern lights and cosmic gamma-ray bursts, occurs so much faster than theory says should be possible. The answer, proposed by researchers at the U.S. Department of Energy’s (DOE) Princeton Plasma Physics Laboratory (PPPL) and Princeton University, could aid forecasts of space storms, explain several high-energy astrophysical phenomena, and improve plasma confinement in doughnut-shaped magnetic devices called tokamaks designed to obtain energy from nuclear fusion.

    Magnetic reconnection takes place when the magnetic field lines embedded in a plasma — the hot, charged gas that makes up 99 percent of the visible universe — converge, break apart and explosively reconnect. This process takes place in thin sheets in which electric current is strongly concentrated.

    According to conventional theory, these sheets can be highly elongated and severely constrain the velocity of the magnetic field lines that join and split apart, making fast reconnection impossible. However, observation shows that rapid reconnection does exist, directly contradicting theoretical predictions.

    Detailed theory for rapid reconnection

    Now, physicists at PPPL and Princeton University have presented a detailed theory for the mechanism that leads to fast reconnection. Their paper, published in the journal Physics of Plasmas in October, focuses on a phenomenon called “plasmoid instability” to explain the onset of the rapid reconnection process. Support for this research comes from the National Science Foundation and the DOE Office of Science.

    Plasmoid instability, which breaks up plasma current sheets into small magnetic islands called plasmoids, has generated considerable interest in recent years as a possible mechanism for fast reconnection. However, correct identification of the properties of the instability has been elusive.

    The Physics of Plasmas paper addresses this crucial issue. It presents “a quantitative theory for the development of the plasmoid instability in plasma current sheets that can evolve in time” said Luca Comisso, lead author of the study. Co-authors are Manasvi Lingam and Yi-Ming Huang of PPPL and Princeton, and Amitava Bhattacharjee, head of the Theory Department at PPPL and Princeton professor of astrophysical sciences.

    Pierre de Fermat’s principle

    The paper describes how the plasmoid instability begins in a slow linear phase that goes through a period of quiescence before accelerating into an explosive phase that triggers a dramatic increase in the speed of magnetic reconnection. To determine the most important features of this instability, the researchers adapted a variant of the 17th century “principle of least time” originated by the mathematician Pierre de Fermat.

    Use of this principle enabled the researchers to derive equations for the duration of the linear phase, and for computing the growth rate and number of plasmoids created. Hence, this least-time approach led to a quantitative formula for the onset time of fast magnetic reconnection and the physics behind it.

    The paper also produced a surprise. The authors found that such relationships do not reflect traditional power laws, in which one quantity varies as a power of another. “It is common in all realms of science to seek the existence of power laws,” the researchers wrote. “In contrast, we find that the scaling relations of the plasmoid instability are not true power laws – a result that has never been derived or predicted before.”

    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. The Laboratory is managed by Princeton 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.energy.gov.

    See the full article here .

    Please help promote STEM in your local schools.

    STEM Icon

    Stem Education Coalition
    Princeton University Campus

    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 12:21 pm on October 14, 2016 Permalink | Reply
    Tags: Alcator C-Mod tokamak, Fusion technology,   

    From MIT: “New record for fusion” 

    MIT News

    MIT Widget
    MIT News

    October 14, 2016
    Plasma Science and Fusion Center

    Alcator C-Mod tokamak nuclear fusion reactor sets world record on final day of operation.

    On Friday, Sept. 30, at 9:25 p.m. EDT, scientists and engineers at MIT’s Plasma Science and Fusion Center made a leap forward in the pursuit of clean energy. The team set a new world record for plasma pressure in the Institute’s Alcator C-Mod tokamak nuclear fusion reactor. Plasma pressure is the key ingredient to producing energy from nuclear fusion, and MIT’s new result achieves over 2 atmospheres of pressure for the first time.

    1
    The interior of the fusion experiment Alcator C-Mod at MIT recently broke the plasma pressure record for a magnetic fusion device. The interior of the donut-shaped device confines plasma hotter than the interior of the sun, using high magnetic fields. Postdoc Ted Golfinopoulos, shown here, is performing maintenance between plasma campaigns. Photo: Bob Mumgaard/Plasma Science and Fusion Center

    Alcator leader and senior research scientist Earl Marmar will present the results at the International Atomic Energy Agency Fusion Energy Conference, in Kyoto, Japan, on Oct. 17.

    Nuclear fusion has the potential to produce nearly unlimited supplies of clean, safe, carbon-free energy. Fusion is the same process that powers the sun, and it can be realized in reactors that simulate the conditions of ultrahot miniature “stars” of plasma — superheated gas — that are contained within a magnetic field.


    Access mp4 video here .
    Video: MIT Plasma Science and Fusion Center
    Nuclear fusion has the potential to produce nearly unlimited supplies of clean, safe, carbon-free energy. This 360-degree tour provides look at MIT’s recently deactivated Alcator C-Mod tokamak nuclear fusion reactor, which set a world pressure record on its final day of operation.

    For over 50 years it has been known that to make fusion viable on the Earth’s surface, the plasma must be very hot (more than 50 million degrees), it must be stable under intense pressure, and it must be contained in a fixed volume. Successful fusion also requires that the product of three factors — a plasma’s particle density, its confinement time, and its temperature — reaches a certain value. Above this value (the so-called “triple product”), the energy released in a reactor exceeds the energy required to keep the reaction going.

    Pressure, which is the product of density and temperature, accounts for about two-thirds of the challenge. The amount of power produced increases with the square of the pressure — so doubling the pressure leads to a fourfold increase in energy production.

    During the 23 years Alcator C-Mod has been in operation at MIT, it has repeatedly advanced the record for plasma pressure in a magnetic confinement device. The previous record of 1.77 atmospheres was set in 2005 (also at Alcator C-Mod). While setting the new record of 2.05 atmospheres, a 15 percent improvement, the temperature inside Alcator C-Mod reached over 35 million degrees Celsius, or approximately twice as hot as the center of the sun. The plasma produced 300 trillion fusion reactions per second and had a central magnetic field strength of 5.7 tesla. It carried 1.4 million amps of electrical current and was heated with over 4 million watts of power. The reaction occurred in a volume of approximately 1 cubic meter (not much larger than a coat closet) and the plasma lasted for two full seconds.

    Other fusion experiments conducted in reactors similar to Alcator have reached these temperatures, but at pressures closer to 1 atmosphere; MIT’s results exceeded the next highest pressure achieved in non-Alcator devices by approximately 70 percent.

    While Alcator C-Mod’s contributions to the advancement of fusion energy have been significant, it is a science research facility. In 2012 the DOE decided to cease funding to Alcator due to budget pressures from the construction of ITER. Following that decision, the U.S. Congress restored funding to Alcator C-Mod for a three-year period, which ended on Sept. 30.

    “This is a remarkable achievement that highlights the highly successful Alcator C-Mod program at MIT,” says Dale Meade, former deputy director at the Princeton Plasma Physics Laboratory, who was not directly involved in the experiments. “The record plasma pressure validates the high-magnetic-field approach as an attractive path to practical fusion energy.”

    “This result confirms that the high pressures required for a burning plasma can be best achieved with high-magnetic-field tokamaks such as Alcator C-Mod,” says Riccardo Betti, the Robert L. McCrory Professor of Mechanical Engineering and Physics and Astronomy at the University of Rochester.

    Alcator C-Mod is the world’s only compact, high-magnetic-field fusion reactor with advanced shaping in a design called a tokamak (a transliteration of a Russian word for “toroidal chamber”), which confines the superheated plasma in a donut-shaped chamber. C-Mod’s high-intensity magnetic field — up to 8 tesla, or 160,000 times the Earth’s magnetic field — allows the device to create the dense, hot plasmas and keep them stable at more than 80 million degrees. Its magnetic field is more than double what is typically used in other designs, which quadruples its ability to contain the plasma pressure.

    C-Mod is third in the line of high-magnetic-field tokamaks, first advocated by MIT physics professor Bruno Coppi, to be built and operated at MIT. Ron Parker, a professor of electrical engineering and computer science, led its design phase. Professor Ian Hutchinson of the Department of Nuclear Science and Engineering led its construction and the first 10 years of operation through 2003.

    Unless a new device is announced and constructed, the pressure record just set in C-Mod will likely stand for the next 15 years. ITER, a tokamak currently under construction in France, will be approximately 800 times larger in volume than Alcator C-Mod, but it will operate at a lower magnetic field. ITER is expected to reach 2.6 atmospheres when in full operation by 2032, according to a recent Department of Energy report.

    Alcator C-Mod is also similar in size and cost to nontokamak magnetic fusion options being pursued by private fusion companies, though it can achieve pressures 50 times higher. “Compact, high-field tokamaks provide another exciting opportunity for accelerating fusion energy development, so that it’s available soon enough to make a difference to problems like climate change and the future of clean energy — goals I think we all share,” says Dennis Whyte, the Hitachi America Professor of Engineering, director of the Plasma Science and Fusion Center, and head of the Department of Nuclear Science and Engineering at MIT.

    These experiments were planned by the MIT team and collaborators from other laboratories in the U.S. — including the Princeton Plasma Physics Laboratory, the Oak Ridge National Laboratory, and General Atomics — and conducted on the Alcator C-Mod’s last day of operation. The Alcator C-Mod facility, which officially closed after 23 years of operation on Sept. 23, leaves a profound legacy of collaboration. The facility has contributed to more than 150 PhD theses and dozens of interinstitutional research projects.

    To understand how Alcator C-Mod’s design principles could be applied to power generation, MIT’s fusion group is working on adapting newly available high-field, high-temperature superconductors that will be capable of producing magnetic fields of even greater strength without consuming electricity or generating heat. These superconductors are a central ingredient of a conceptual pilot plant called the Affordable Robust Compact (ARC) reactor, which could generate up to 250 million watts of electricity.

    See the full article here .

    Please help promote STEM in your local schools.

    STEM Icon

    Stem Education Coalition

    MIT Seal

    The mission of MIT is to advance knowledge and educate students in science, technology, and other areas of scholarship that will best serve the nation and the world in the twenty-first century. We seek to develop in each member of the MIT community the ability and passion to work wisely, creatively, and effectively for the betterment of humankind.

    MIT Campus

     
  • richardmitnick 11:44 am on October 12, 2016 Permalink | Reply
    Tags: Data drive quests to control nuclear fusion, Fusion technology, ,   

    From PPPL via Princeton University: “Data drive quests to control nuclear fusion” 

    Princeton University
    Princeton University

    10.12.16
    John Sullivan

    1
    Egemen Kolemen (left), assis- tant professor of mechanical and aerospace engineering, speaks with Al von Halle, head of engineering and operations for NSTX-U, a major experiment in nuclear fusion being conducted at the Princeton Plasma Physics Laboratory.

    PPPLII

    PPPL NSTX
    PPPL/NSTX

    Running a fusion reactor is like holding part of the sun in a bottle its heart is a raging storm of particles trapped in a magnetic field.

    To translate this storm’s power into a practical energy source, scientists will have to harness and control the reactor by adjusting the twists and flows of its superheated particles.

    “Plasma can destabilize in milliseconds,” said Egemen Kolemen *08, an assistant professor in mechanical and aerospace engineering and the Andlinger Center for Energy and the Environment. “To control the reaction, we need to react in the same timescale.”

    Kolemen is one of several Princeton engineers working with colleagues at the Princeton Plasma Physics Laboratory (PPPL), a U.S. Department of Energy lab administered by Princeton University, to solve critical problems in making fusion energy a practical reality. In particular, Kolemen and Clarence Rowley ’95, a professor of mechanical and aerospace engineering, lead separate projects to control the behavior of a state of matter known as plasma.

    Instant decisions

    A fusion reactor starts by heating light atoms such as hydrogen gas far beyond the temperature of the sun. At such temperatures, electrons fly free of their atoms leaving a swirl of electrically charged particles called plasma. If engineers can arrange this plasma into just the proper configuration, the particles will slam into each other and fuse into new types of matter, releasing massive amounts of energy. Scientists have been able to do this for minutes at a time, but maintaining a stable reaction for a fusion power plant that needs months to years of operation is a different story. The plasma constantly seeks to fling itself apart. Even if operators prevent this, they still have to control the plasma’s constant twists and swirls to maximize the collisions among particles.

    To make things more complex, there is no easy way to take real-time measurements of plasma’s configuration – observations are possible, but they take time to analyze. That is where Kolemen’s work begins.

    “We gather pieces of diagnostic measurements and quantify the uncertainty,” he said. “We try to put all this information in physics models and figure out what the situation is in the reactor.”

    Kolemen is assembling algorithms that will evaluate measurements of the plasma and make rapid calculations that trigger minute shifts in the reactor. The goal is to create an automated system that reacts quickly enough to maintain stability within the plasma.

    “You need to understand all of the diagnostics, analyze them with the physics, predict if there is going to be a disruption, and take action,” he said.

    It might sound impossible, but Kolemen said the framework of the system is in place. He said engineers are now working to build up the system and increase its reliability.

    “Making something so it works once in a while is easy,” he said. “Going from a system that is functional for 90 percent of the time to the more than 99.99 percent reliability needed for a fusion power plant – that requires a bit more thinking.”

    2
    Clarence Rowley (left) and graduate student Imène Goumiri built on data from previous experiments in nuclear fusion to develop a method to reduce turbulence in the chaotic swarm of ultra-hot particles known as plasma, which is necessary for producing fusion power.

    Finding flow

    While Kolemen seeks tools to control plasmas as they change, Rowley is developing mathematical models that reveal why instabilities develop in the first place.

    To an untrained eye, the plasma seems to twist and roll randomly, but Rowley said that underlying patterns often hide in a multitude of details.

    “If you really want to understand what is going on, to get to the heart of the matter, you want to strip away those details,” Rowley said. “Often, it’s something simple.”

    Imène Goumiri, a graduate student in Rowley’s lab, recently worked with colleagues at Princeton and PPPL to develop a system using mathematical modeling and high-speed controls to reduce turbulence in plasmas created in the lab. Built on data from previous experiments, the program reacts quickly to changes in the plasma’s flow and reduces instabilities by rotating sections of the plasma at different speeds.

    Rowley’s team has revealed how small changes that occur at critical locations and are amplified by other factors. The amplification can eventually cause the small change to play a big role in the overall flow.

    “Trying to identify the features of the flow that are very sensitive to change is a big part of this business,” Rowley said. “Even though this is about fluid dynamics or plasma, it can apply to any domain, which is why it is useful to think about it in a mathematical framework. For instance, if you are trying to understand instabilities in a power grid that could lead to blackouts, you want to know if there are places in the grid that are really vulnerable if one generator went off, it could send ripples through the grid. These same techniques could give you a better understanding of that as well.”

    See the full article here .

    Please help promote STEM in your local schools.

    STEM Icon

    Stem Education Coalition
    Princeton University Campus

    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 4:38 pm on September 29, 2016 Permalink | Reply
    Tags: , Director Stewart Prager steps down after nSTX failure, Fusion technology, Physics Today insert,   

    From PPPL: “PPPL Director Stewart Prager Steps Down” 


    PPPL

    September 26, 2016
    Larry Bernard

    Prof. Stewart Prager, a world renowned plasma physicist and passionate voice for a future of clean, abundant and benign energy fueled by fusion, has stepped down today from directorship of the national laboratory he has headed for the last eight years.

    [But two sources who declined to be identified said DOE had forced Prager’s resignation; one source called the move an example of the agency’s “buck stops here” contractor management philosophy. A second source corroborates that account: “This was a firing as much as anything else.”]

    Prager denies that he was asked to resign. “I never spoke to the Office of Science,” he says, adding he had only discussed his resignation with officials at Princeton University, which operates PPPL for DOE. Prager, who is also a professor of astrophysics at Princeton, says he had been considering stepping down since January.

    The NSTX-U has been shut down since the end of July, when one of the machine’s 14 magnets, a poloidal field coil, shorted out after 10 weeks of running time, says Mike Zarnstorff, PPPL deputy director for research. Replacing it, and a second identical coil on the opposite side of the tokamak chamber, will take about a year, he says. The machine was nearly due for a scheduled six-month shutdown for maintenance, he notes.

    The NSTX-U, a $94 million upgrade of a reactor built in 1999, is the world’s most powerful spherical tokamak, with a design field strength of 1 T and heating power of 10–12 MW. It is a variant of the mainstream tokamak technology at laboratories such as the UK’s Joint European Torus and the ITER international fusion collaboration in France. Tokamaks use magnetic fields to bottle up plasmas of hydrogen isotopes, which heats the confined particles to tens of millions of degrees and causes them to fuse into helium.

    Zarnstorff says the root cause of the coil failure is still unknown, although he suspects it was a manufacturing problem. A source close to the lab says the copper wire used in the coil may have been too stiff to accommodate a particular bend in the winding.

    The tokamak was operating at half its maximum design field strength when the problem occurred, Zarnstorff says, and full field operation wasn’t planned until next year. The lab has identified four design simplifications to mitigate risks in the replacement coils. A second defect, a damaged copper cooling tube, was discovered when the machine was taken apart. “We know that copper was an unwise choice,” Zarnstorff says. “It should have been made of stainless steel.”

    During the shutdown, the lab will review the entire NSTX-U design to determine how to implement beneficial design changes and mitigate further risks. “We’ll have to wait and see and do the [analysis] work,” Zarnstorff says.
    David Kramer, Physics Today]

    “It has been a wonderful experience being lab director of the Princeton Plasma Physics Laboratory. But, at the seven-year mark last January I began to think about moving on to the next phase of my life,” Prager said. “The recent technical setback in the NSTX-U facility unexpectedly and suddenly defines a moment that seems to me appropriate for that transition.

    PPPL NSTXII
    NSTX

    It is best for new, continuing leadership to shepherd the rebuilding of the facility and the engineering changes that will be needed over the next year.”

    Prager, the sixth director in the 65-year history of PPPL, joined the Lab in the fall of 2008 after a long career at the University of Wisconsin. A pioneer in plasma physics, he is internationally known for experiments that contribute to the fundamental knowledge of fusion energy and the design of devices that will produce it.

    A professor in the department of astrophysical sciences at Princeton University, Prager will continue research activity at PPPL in fusion energy and plasma physics, beginning with a year’s sabbatical.

    Prof. Dave McComas, Princeton vice president for PPPL, joined Princeton University President Christopher L. Eisgruber in thanking Prager for his dedication to fusion and plasma science. “We are truly grateful to Stewart for his many outstanding contributions and dedicated leadership over the past eight years,” McComas said.

    McComas praised Prager for his leadership in several key initiatives. Among them: founding the Max Planck-Princeton Center for Plasma Physics; increasing joint faculty appointments between Princeton and the Lab; increasing ties between University departments and the Laboratory; developing a fusion communications strategy; broadening the Laboratory’s engagement in low-temperature plasma physics, plasma nanomaterials, laboratory astrophysics, computational fusion science and high energy density physics; and launching a campus plan to modernize the PPPL infrastructure.

    Prof. A.J. Stewart Smith, the former Princeton Vice President for PPPL, said:

    “For more than seven years it has been my great honor and pleasure to work with Stewart, and give whatever assistance I could. In 2008 Stewart towered above the other candidates when we were searching for Rob Goldston’s successor, so we were simply thrilled when he agreed to head the leadership team we proposed to DOE in the competition for the PPPL contract. Stewart’s intelligent but gentle leadership and tireless efforts on behalf of PPPL and the U.S. fusion community have greatly improved communication and cooperation among U.S. fusion institutions. He has also been and continues to be a constant driving force in building an exciting new U.S. research effort to establish stellarators as a strong alternative to tokamaks for practical fusion reactors. I wish him all the best, and great success as he resumes his distinguished scientific career after so many years of dedication to the laboratory. He will be a most difficult act to follow.”

    Dr. Terry Brog, who recently joined the laboratory as deputy director for operations and chief operating officer (COO) at PPPL, will be interim director of the Lab. Dr. Stacia Zelick, chief information officer and head of information technology, will be interim deputy director of operations and COO as the global search for Prager’s successor begins. Dr. Mike Zarnstorff, deputy director for research, will continue to serve in that role.

    PPPL is a DOE national laboratory operated by Princeton University, and the only national lab dedicated to fusion research and plasma science. NSTX-U is a spherical tokamak, or fusion device, producing plasmas many times hotter than the center of the sun to explore the development of fusion as a safe, clean, and abundant energy source to generate electricity for the world. The compact facility confines high pressure plasma in relatively low and cost-effective magnetic fields, and could serve as a model for the next major step in the U.S. fusion program.

    See the full article here .

    Please help promote STEM in your local schools.

    STEM Icon

    Stem Education Coalition

    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.energy.gov.

     
  • richardmitnick 10:09 pm on September 12, 2016 Permalink | Reply
    Tags: , Fusion technology, Hanna Schamis, ,   

    From PPPL: Women in STEM – “PPPL internship inspires grad student intern to pursue plasma physics” Hanna Schamis 


    PPPL

    September 9, 2016
    Jeanne Jackson DeVoe

    1
    Hanna Schamis, a Science Undergraduate Laboratory intern at PPPL, in front of the National Spherical Torus Experiment-Upgrade (NSTX-U)

    When Hanna Schamis packed her bags for graduate school this summer, she already had two summers of hands-on research under her belt as an intern at the U.S. Department of Energy’s (DOE) Princeton Plasma Physics Laboratory (PPPL) and had decided on a career in plasma physics.

    Schamis recently began graduate school at the University of Illinois at Urbana-Champaign (UIUC) after completing her second Science Undergraduate Laboratory Internship (SULI) at PPPL. She plans to study in the Department of Nuclear, Plasma, and Radiological Engineering, and continue the research she started at PPPL on the effect of plasmas on materials that could be used for the walls of fusion devices to protect them from the intense heat and high flux of particles that emanate from plasmas, which can reach temperatures of up to 100 million degrees – hotter than the sun.

    A change in career path

    Schamis’ first summer at PPPL changed her career path, and the current project is more in line with her research interests. “When I first arrived at SULI last year I wasn’t very aware of everything going on in plasma research,” Schamis said. “Through the lectures and seminars, I started getting really interested in plasma material interactions so I ended up choosing that path.”

    She may have chosen wisely, as finding a wall material that is long lasting and won’t affect the behavior of the ultra-hot plasma inside a reactor is one of the greatest challenges of fusion energy research. Such research, on the National Spherical Torus Experiment-Upgrade (NSTX-U) at PPPL and on other tokamaks, can help in understanding how once a burning plasma is achieved – such as that planned at the international fusion experiment under construction in France, ITER – a fusion reactor can be built with a durable wall.

    ITER Tokamak
    ITER Tokamak, France

    A physics major as an undergraduate at the University of Michigan-Ann Arbor, Schamis said she liked the hands-on nature of the SULI program. “I like that it’s applied research and it has applications in the real world,” she said.

    Schamis’ research this summer focused on an alloy of molybdenum (TZM), a substance that will be used to line the divertor, a part of the machine that collects heat and particles from the plasma. TZM could eventually be used to line the walls of the NSTX-U.

    PPPL NSTXII
    PPPL NSTX

    TZM is a strong, heat-resistant material. It would avoid the problem of the plasma eroding the carbon that makes up graphite walls like those presently in the NSTX-U. This would be a serious problem in a reactor that runs for long periods of time like ITER.

    Research on device attached to NSTX-U

    Schamis used a device called the Material Analysis and Particle Probe (MAPP), developed by the University of Illinois at Urbana-Champaign, to conduct her experiment and analyze the results.

    2
    Physicists at the U.S. Department of Energy’s (DOE) Princeton Plasma Physics Laboratory (PPPL) have successfully tested a new device that will lead to a better understanding of the interactions between ultrahot plasma contained within fusion facilities and the materials inside those facilities. The measurement tool, known as the Materials Analysis Particle Probe (MAPP), was built by a consortium that includes Princeton University and the University of Illinois at Urbana-Champaign (U. of I.).

    MAPP is attached to the bottom of NSTX-U in the divertor, and inserts samples of plasma into the machine during experiments. The samples can then be retracted into a vacuum chamber that is part of MAPP. This chamber is fitted with an apparatus for x-ray photoelectron spectroscopy (XPS). XPS is performed by shooting x-rays at the sample, and measuring the energies of the electrons emitted by the elements on the surface. This allowed Schamis to analyze the effect of the plasma on the chemical composition of the TZM over time.

    “This is the first time measurements of this kind have been performed on a large fusion device like NSTX-U. Since they were made while the samples were still in a chamber that was connected to NSTX-U, changes of the chemistry of the wall could be more readily correlated to changes in the plasma itself,” said PPPL physicist Robert Kaita, Schamis’ mentor on the project.

    See the full article here .

    Please help promote STEM in your local schools.

    STEM Icon

    Stem Education Coalition

    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.energy.gov.

     
  • richardmitnick 9:30 am on September 12, 2016 Permalink | Reply
    Tags: , Fusion technology, MAPP,   

    From PPPL: “PPPL researchers successfully test new device that analyzes the surfaces of tokamak components within a vacuum” 


    PPPL

    September 9, 2016
    Raphael Rosen

    1

    Physicists at the U.S. Department of Energy’s (DOE) Princeton Plasma Physics Laboratory (PPPL) have successfully tested a new device that will lead to a better understanding of the interactions between ultrahot plasma contained within fusion facilities and the materials inside those facilities. The measurement tool, known as the Materials Analysis Particle Probe (MAPP), was built by a consortium that includes Princeton University and the University of Illinois at Urbana-Champaign (U. of I.).

    The device lets scientists test the chemical make-up of the surface of materials exposed to plasma, while keeping the materials in a vacuum. The research was published in the July issue of Review of Scientific Instruments, and was funded by the DOE Office of Science (Fusion Energy Sciences) and the Francisco José de Caldas Fellowship Program.

    MAPP’s leading developer is Professor Jean Paul Allain, now at the U. of I., who began the project in 2011. Collaborators at PPPL include physicists Robert Kaita, Charles Skinner, and Bruce Koel.

    “Using MAPP, we are seeing for the first time the evolution of the materials when they interact with the plasma, and how the conditioning and other procedures modify the chemistry of the materials,” said lead author Felipe Bedoya, a graduate student in the Department of Nuclear, Plasma and Radiological Engineering at the U. of I. Bedoya spent a semester at PPPL investigating the relationship between the conditioning of plasma-facing components (PFCs) and the behavior of plasma in the National Spherical Torus Experiment-Upgrade (NSTX-U), the nation’s newest fusion device and the flagship fusion facility at PPPL.

    PPPL NSTXII
    NSTX at PPPL

    The interactions between the plasma and the inner walls of the tokamak are crucially important to the production of fusion energy because they profoundly affect the condition of the plasma. If hot hydrogen ions in the plasma touch the walls, the ions are absorbed and cool down. And if the cool hydrogen re-enters the plasma, it lowers the temperature of the plasma’s edge and fusion reactions within the plasma occur less often.

    In addition, the interior of a tokamak can be eroded by the bombardment of the plasma ions. The amount of plasma-wall interactions can also determine how long a tokamak’s plasma-facing components can last before being replaced. Understanding the behavior of materials when exposed to plasma is therefore critical for the design of future fusion machines.

    Before MAPP, scientists had to wait for the completion of a long series of fusion experiments before analyzing materials within a tokamak. That kept researchers from confidently correlating fusion experiments their effect on the materials. And because samples of the material had to be exposed to air when they were brought to a laboratory, scientists couldn’t be sure that the chemistry of the samples had not changed.

    MAPP enables material samples to be measured under vacuum conditions after each experiment. “People used to wait until the end of an experiment campaign to take out a tile, bring it to a lab, and examine it,” said Bedoya. “What we’re doing right now is bringing the lab to the machine.”

    MAPP has been in operation on the NSTX-U for the last 10 months. While using MAPP, researchers expose a set of material samples conditioned with boron to the NSTX-U plasma and retract the samples into a vacuum chamber without any exposure to air. They then use a technique called “X-ray photoelectron spectroscopy” to strike the samples with X-rays and study the electrons the process emits. The emissions provide information about the surface chemistry of the samples, revealing how the boron coating changes when exposed to the plasma.

    In the paper, the authors report that they successfully tested a method to analyze data produced by MAPP. They used a sophisticated computer program called CasaXPS to obtain the proper interpretation. Results appear to have matched both controlled laboratory experiments and computer simulations, suggesting that the technique’s analysis is correct.

    “Many people have seen a strong correlation between the conditioning of the plasma-facing components and the performance of the plasma,” Bedoya said. “So if you can diagnose how the conditioning changes, you can do it better and better each time and ultimately figure out the optimum conditioning.”

    Scientists believe that MAPP will become an integral part of plasma physics research. “MAPP is a step towards uncovering the mysteries of what’s happening at tokamak walls, shot by shot, as the wall changes the plasma’s conditions,” said Charles Skinner, PPPL physicist and co-author of the paper. “Using this device could help us see exactly what’s going on at the wall, and how that correlates or even explains what’s going on with the plasma.”

    See the full article here .

    Please help promote STEM in your local schools.

    STEM Icon

    Stem Education Coalition

    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.energy.gov.

     
  • richardmitnick 2:08 pm on August 25, 2016 Permalink | Reply
    Tags: , Fusion technology, ,   

    From PPPL: “How to keep the superhot plasma inside tokamaks from chirping” 


    PPPL

    August 19, 2016
    Raphael Rosen

    1
    Graduate student Vinícius Duarte. (Photo by Elle Starkman)

    Chirp, chirp, chirp.” The familiar sound of birds is also what researchers call a wave in plasma that breaks from a single note into rapidly changing notes. This behavior can cause heat in the form of high energy particles — or fast ions — to leak from the core of plasma inside tokamaks — doughnut-shaped facilities that house fusion reactions.

    PPPL NSTXII
    NSTX tokamak at PPPL

    Physicists want to prevent these waves from chirping because they may cause too many fast ions to escape, cooling the plasma. As the plasma cools, the atomic nuclei in the tokamak are less likely to come together and release energy and the fusion reactions will sputter to a halt.

    “Chirping modes can be very harmful because they can steal energy from the fast ions in an extended region of the plasma,” said Vinícius Duarte, a graduate student from the University of São Paulo. Duarte is at the U.S. Department of Energy’s (DOE) Princeton Plasma Physics Laboratory (PPPL) conducting research for his dissertation. Support for this work comes from the DOE Office of Science.

    Chirping modes often have frequencies far above what the human ear can hear. The name — “chirping” — stems from the change in the waves’ frequency over time. Typically, the modes start with a high frequency and drop down in frequency very rapidly. The chirping of modes has been studied for decades as physicists seek to understand and eliminate them.

    In a recent theoretical study, Duarte discovered some conditions within plasma that can make the chirping of modes more likely. A paper he is preparing on this topic explains the phenomenon and may help to optimize the design of fusion energy plants in the future. Collaborating on the research were physicists at PPPL, General Atomics, the University of California-Irvine, and the University of Texas at Austin. Physicist Nikolai Gorelenkov, Duarte’s PPPL advisor, introduced him to the software code that enabled this work, Prof. Herbert Berk of the University of Texas co-advised on the project and researchers from the DIII-D National Fusion Facility that General Atomics operates for the DOE provided the data for comparison with the theory.

    The researchers began by noting that the chirping of modes seems to occur in some tokamaks more often than in others. They are rare in the DIII-D tokamak, for example, but were common in the National Spherical Torus Experiment (NSTX), PPPL’s former flagship fusion device, which has recently been upgraded.

    By running simulations on PPPL computers, Duarte and the team found that plasma turbulence — or random fluctuation — was a factor that helped explain the chirping of modes. Chirping can occur when there is a strong concentration of fast ions bunched together, while other particles are widely spaced.

    The surprise is that substantial turbulence can break up concentrations of fast ions, and therefore help to extinguish the chirping of modes.

    The simulations matched the data from experiments. In NSTX, the turbulence has little effect on fast ions and chirping modes are common, whereas DIII-D has relatively high interaction between turbulence and fast ions and chirping modes are rare. In DIII-D, chirping starts only when the interaction between the turbulence and fast-ions markedly decreases.

    These findings could lead to fusion facilities that leak less heat than current machines and could improve the efficiency of ITER, the international tokamak under construction in France to demonstrate the feasibility of fusion power.

    ITER Tokamak
    ITER Tokamak, France

    “In ITER, where fast ions from fusion reactions are expected to sustain a burning plasma, the good confinement of these particles is a crucial issue,” said Duarte.

    See the full article here .

    Please help promote STEM in your local schools.

    STEM Icon

    Stem Education Coalition

    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.energy.gov.

     
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: