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  • richardmitnick 8:14 pm on February 15, 2019 Permalink | Reply
    Tags: "Looking Forward to Fusion", , , Fusion technology, MIT Spectrum, Patrick White,   

    From MIT Spectrum: “Looking Forward to Fusion” 

    MIT Widget

    From MIT Spectrum

    Winter 2019

    1
    Patrick White (photographed in the Plasma Science and Fusion Center) is focused on the policy questions that will arise from the new SPARC technology. Photo: Bryce Vickmark

    Technical policy scholar Patrick White joins the SPARC project to ask: what comes after success?

    Controlled fusion power has been a tantalizing prospect for decades, promising a source of endless carbon-free energy for the world. Unfortunately, persistent technical challenges have kept that achievement on an ever-receding horizon. But recent developments in materials science and superconductivity have changed the landscape. The proposed SPARC experiment of MIT’s Plasma Science and Fusion Center (PSFC), in collaboration with the private, MIT alumni-led company Commonwealth Fusion Systems, is poised to use those breakthroughs to build the first fusion device that generates more energy than it consumes, bringing commercial fusion energy within practical reach in the near future.

    MIT SPARC fusion reactor tokamak

    Patrick White, a PhD candidate in the Department of Nuclear Science and Engineering (NSE), is looking ahead to that long-awaited day. His PhD project, funded by the Samuel W. Ing (1953) Memorial Fellowship in the NSE department and PSFC, anticipates the many questions that will follow a successful SPARC project and the development of fusion power.

    “How do you commercialize this technology that no one’s ever built before?” he asks. “It’s an opportunity to start from scratch.” White is focusing on the regulatory structures and safety analysis tools that will be necessary to bring fusion power plants out of the laboratory and onto the national power grid.

    He first became fascinated with nuclear science and technology while studying mechanical engineering at Carnegie Mellon University. “I think it was the fact that you can take a gram of uranium and release the same energy as several tons worth of coal, or that a single nuclear reactor can power a million homes for 60 years,” he remembers. “That absolutely blew me away.” He saw commercial reactor technology up close during an undergraduate summer internship with Westinghouse, and followed that with two summers in Washington, DC, working with the Defense Nuclear Facilities Safety Board.

    When White came to MIT for graduate work, he joined the MIT Energy Initiative’s major interdisciplinary study, The Future of Nuclear Energy in a Carbon-Constrained World, authoring the regulation and licensing section of the final report (which was subsequently released this past September). He began casting about for a PhD topic around the time the SPARC project was announced.

    The goal of SPARC is to demonstrate net energy from a fusion device in seven years—a key technical milestone that could lead to the construction of a commercially viable power plant scaled up to roughly twice SPARC’s diameter. Because the fusion process produces net energy at extreme temperatures no solid material can withstand, fusion researchers use magnetic fields to keep the hot plasma from coming into contact with the device’s chamber. Currently, the team building SPARC is refining the superconducting magnet technology that will be central to its operation. Already familiar with the regulatory and safety framework that’s been developed over decades of commercial fission reactor operation, White immediately began considering the challenges of regulating an entirely new potential technology that hasn’t yet been invented. One concern in the fusion community, he notes, is that “before we even have a final plant design, the regulatory system could make the ultimate device too expensive or too cumbersome to actually operate. So we’ll be looking at existing nuclear and non-nuclear industries, how they think about safety and regulation, and trying to come up with a pathway that makes the most sense for this new technology.”

    His PhD project proposal on the regulation of commercial fusion plants was selected by the PSFC for funding, and he got down to work in fall 2018 under three advisors: Zach Hartwig PhD ’14, the John C. Hardwick Assistant Professor of Nuclear Science and Engineering; assistant professor Koroush Shirvan SM ’10, PhD ’13; and Dennis Whyte, director of PSFC and the Hitachi America Professor of Engineering.

    White’s career plans beyond the fellowship remain flexible: he notes that whether he ends up working with the licensing of advanced fission reactors or in the new world of commercial fusion power will depend on the technology itself, and how SPARC and other experimental projects evolve. Another possibility is bridging the communications gap between the nuclear industry and a public that’s often apprehensive about nuclear technology: “At the end of the day, if people refuse to have it built in their backyard, you’ve got a great device that can’t actually do any good.”

    For now, White’s fellowship is not only laying the groundwork for his own future, but also perhaps the future of what would be one of the greatest technological advances of humankind. He points out that the stakes are higher than simply developing a new energy technology. “If we’re really concerned about climate change and decarbonizing, we need to have every single tool on the table,” he says. “The more tools, the better.”

    See the full article here .


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  • richardmitnick 4:05 pm on January 31, 2019 Permalink | Reply
    Tags: , Fusion technology, , Rochester’s laser lab moves closer to controlled nuclear fusion, , With data science   

    From University of Rochester: “With data science, Rochester’s laser lab moves closer to controlled nuclear fusion” 

    U Rochester bloc

    From University of Rochester

    U Rochester Omega Laser

    Scientists have been working for decades to develop controlled nuclear fusion. Controlled nuclear fusion would improve the ability to evaluate the safety and reliability of the nation’s stockpile of nuclear weapons—in labs in lieu of actual test detonations. And ultimately, it could produce an inexhaustible supply of clean energy.

    But the challenges have been many. Notably, designing optimal fusion experiments requires accurately modeling all of the complex physical processes that occur during an implosion. One of the biggest handicaps has been the lack of accurate predictive models to show in advance how target specifications and laser pulse shapes might be altered to increase fusion energy yields.

    Now researchers at the University of Rochester’s Laboratory for Laser Energetics (LLE), along with colleagues from MIT, have been able to triple fusion yields by bringing data science techniques to previously collected data and computer simulations.

    Approaching a fusion milestone

    Rochester’s Laboratory for Laser Energetics is the largest university-based US Department of Energy program in the nation and is home to the OMEGA laser, the most powerful laser system found at any academic institution.

    U Rochester OMEGA EP Laser System

    The facility has taken the lead in the laser direct-drive approach to fusion energy by blasting spherical deuterium-tritium fuel pellets with 60 laser beams, converging directly on the pellet surface from all directions at once. This causes the pellet to heat and implode, forming a plasma. If sufficiently high temperatures and pressures could be confined at the center of the implosion, a thermonuclear burn wave would propagate radially through the entire fuel mass, producing fusion energy yields many times greater than the energy input.

    The latest increase in yields, reported in Nature, bring scientists closer to an important milestone in their quest to achieve controlled thermonuclear fusion – getting the plasma to self-ignite, enabling an output of fusion energy that equals the laser energy coming in.

    “That would be a major achievement but it will require energies much larger than the OMEGA laser such as at the NIF at Lawrence Livermore National Laboratory,” says Michael Campbell, LLE’s director.


    National Ignition Facility at LLNL

    Bridging the gap between experiments and simulations

    To create a predictive model, Varchas Gopalaswamy and Dhrumir Patel, PhD students in mechanical engineering, and their supervisor Riccardo Betti, chief scientist and Robert L . McCrory Professor at LLE, applied data science techniques to results from about 100 previous fusion experiments at OMEGA.

    “We were inspired from advances in machine learning and data science over the last decade,” Gopalaswamy says. Adds Betti: “This approach bridges the gap between experiments and simulations to improve the predictive capability of the computer programs used in the design of experiments.”

    The statistical analysis guided LLE scientists in altering the target specifications and temporal shape of the laser pulse used in the fusion experiments. The task required a concerted effort by LLE experimental physicists who set up the experiments, and theorists who develop the simulation codes. James Knauer, LLE senior scientist, led the experimental campaign.

    “These experiments required exquisite control of the laser pulse shape,” Knauer says. Patel applied the statistical technique to design the laser pulse shape leading to the best performing implosion.

    “This was a very, very unusual pulse shape for us,” Campbell says. And yet, within three or four subsequent experiments, according to Campbell, an experiment was designed that produced 160 trillion fusion reactions, tripling the previous record at OMEGA.

    “Only thanks to the dedication and expertise of the facility crew, target fabrication, cryogenic layering and system scientists, were we able to control the target quality and the laser pulse to the precision required for these experiments,” Betti says.

    Extrapolating to the National Ignition Facility

    When extrapolated to match the 70-times more powerful laser-energies used at the National Ignition Facility (NIF) at Lawrence Livermore National Laboratory, these implosions would be expected to produce about 1,000 times more fusion reactions. Under the right conditions, a modest improvement in target compression on OMEGA could be enough to approach breakeven conditions at NIF energy levels, with the fusion energy output equaling the laser energy input. “Extrapolating the results from OMEGA to NIF is a tricky business. It is not just a size and energy issue. There are also qualitative differences that need to be assessed” Betti said. For this purpose, a parallel effort by LLE scientists in collaboration with colleagues at Lawrence Livermore and the Naval Research Laboratory (NRL) is underway at the NIF to verify that OMEGA results can be extrapolated to NIF energies.

    The NIF is configured for an indirect drive approach to fusion experiments, in which the fuel capsule is enclosed within a metal cylindrical can called a hohlraum. Laser beams enter from the can ends and heat the hohlraum, which in turns produces x-rays that cause the fuel to implode. Unlike OMEGA, NIF beams are not positioned symmetrically, but are instead concentrated along the axis of the hohlraum. The indirect drive scheme has also made major progress in recent experiments at the NIF. “They are getting close to achieve burning-plasma conditions,” Campbell says.

    “The next couple of years we will do experiments on OMEGA using the same asymmetric laser configuration of the NIF, and see what the penalty is.”

    The paper lists a total of 50 LLE scientists and students as coauthors, along with four collaborators from MIT. The target components were made by General Atomics to meet very strict tolerances.

    See the full article here .

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    The University of Rochesteris one of the country’s top-tier research universities. Our 158 buildings house more than 200 academic majors, more than 2,000 faculty and instructional staff, and some 10,500 students—approximately half of whom are women.

    Learning at the University of Rochester is also on a very personal scale. Rochester remains one of the smallest and most collegiate among top research universities, with smaller classes, a low 10:1 student to teacher ratio, and increased interactions with faculty.

     
  • richardmitnick 2:01 pm on January 3, 2019 Permalink | Reply
    Tags: "Nuno Loureiro: Understanding turbulence in plasmas", Fusion technology, , , ,   

    From MIT News: “Nuno Loureiro: Understanding turbulence in plasmas” 

    MIT News
    MIT Widget

    From MIT News

    January 3, 2019
    Peter Dunn

    1
    “When we stimulate theoretically inclined minds by framing plasma physics and fusion challenges as beautiful theoretical physics problems, we bring into the game incredibly brilliant students,” says associate professor of nuclear science and engineering Nuno Loureiro. Photo: Gretchen Ertl

    Theoretical physicist’s focus on the complexity of plasma turbulence could pay dividends in fusion energy.

    Difficult problems with big payoffs are the life blood of MIT, so it’s appropriate that plasma turbulence has been an important focus for theoretical physicist Nuno Loureiro in his two years at the Institute, first as a assistant professor and now as an associate professor of nuclear science and engineering.

    New turbulence-related publications by Loureiro’s research group are contributing to the quest to develop nuclear fusion as a practical energy source, and to emerging astrophysical research that delves into the fundamental mechanisms of the universe.

    Turbulence is around us every day, when smoke rises through air, or milk is poured into coffee. While engineers can draw on substantial empirical knowledge of how it behaves, turbulence’s fundamental principles remain a mystery. Decades ago, Nobel laureate Richard Feynman ’39 referred to it as “the most important unsolved problem of classical physics” — and that still holds true today.

    But turbulence in air or coffee is a simple proposition compared to turbulence in plasma. Ordinary gases and liquids can be modeled as neutral fluids, but plasmas are electromagnetic media. Their turbulent behavior involves both the particles in the plasma (typically electrons and ions, but also electrons and positrons in so-called pair plasmas) and pervading electrical and magnetic fields. In addition, plasmas are often rarefied media where collisions are rare, creating an even more intricate dynamic.

    “There are several additional layers of complexity [in plasma turbulence] over neutral fluid turbulence,” Loureiro says.

    This lack of first-principles understanding is hindering the adaption of fusion for generating electricity. Tokamak-style fusion devices, like the Alcator C-Mod developed at MIT’s Plasma Science and Fusion Center (PSFC), where Loureiro’s research group is based, are a promising approach, and recent the spinout company Commonwealth Fusion Systems (CFS) is working to commercialize the concept. But fusion devices have yet to achieve net energy gain, in large part because of turbulence.

    Alcator C-Mod tokamak at MIT, no longer in operation

    Loureiro and his student Rogério Jorge, with co-author Professor Paolo Ricci from the École Polytechnique Fédérale de Lausanne, Switzerland, recently helped advance thinking in this area in a new paper, “Theory of the Drift-Wave Instability at Arbitrary Collisionality,” published in the journal Physical Review Letters.

    “This was amazing work by a fantastic student — a very complicated calculation that represents a qualitative advancement to the field,” Loureiro says.

    He explains that turbulence in tokamaks changes “flavor” depending on “where you are — at the periphery or near the core.”

    “Both are important, but periphery turbulence has important engineering implications because it determines how much heat reaches the plasma-facing components of the device,” Loureiro says. Preventing heat damage to materials, and maximizing operational life, are key priorities for tokamak developers.

    The paper offers a novel and more-robust description of turbulence in the tokamak periphery caused by low-frequency drift waves, which are a key source of that turbulence and regulators of plasma transport across magnetic fields. And because the computational framework is especially efficient, the approach can be easily extended to other applications. “I think it’s going to be an important piece of work for the fusion concepts that PSFC and CFS are trying to develop,” he says.

    A separate paper, “Turbulence in Magnetized Pair Plasmas,” which Loureiro co-authored with Professor Stanislav Boldyrev of the University of Wisconsin at Madison, puts forward the first theory of turbulence in pair plasmas. The work, published in The Astrophysical Journal Letters, was driven in part by last year’s unprecedented observations of a binary neutron star merger and other discoveries in astrophysics that suggest pair plasmas may be abundant in space — though none has been successfully created on Earth.

    “A variety of astrophysical environments are probably pair-plasma dominated, and turbulent,” notes Loureiro. “Pair plasmas are quite different from regular plasmas. In a normal electron-ion plasma, the ion is about 2,000 times heavier than the electron. But electrons and positrons have exactly the same mass, so there’s a whole range of behaviors that aren’t possible in a normal plasma and vice-versa.”

    Because computational calculations involving equal-weight particles are much more efficient, researchers often run pair-plasma numerical simulations and try to extrapolate findings to electron-ion plasmas.

    “But if you don’t understand how they’re the same or different from a theoretical point of view, it’s very hard to make that connection,” Loureiro points out. “By providing that theory we can help tell which characteristics are intrinsic to pair plasmas and which are shared. Looking at the building blocks may impact electron-ion plasma research too.”

    This theme of theoretical integration characterizes much of Loureiro’s work, and led to his being invited to present at a recent interdisciplinary event for plasma physicists and astrophysicists at New York City’s Flatiron Institute Center for Computational Astrophysics, an arm of a foundation created by billionaire James Simons ’58. It is also central to his role as a theorist within the MIT NSE ecosystem, especially on extremely complex challenges like fusion development.

    “There are people who are driven by technology and engineering, and others who are driven by fundamental mathematics and physics. We need both,” he explains. “When we stimulate theoretically inclined minds by framing plasma physics and fusion challenges as beautiful theoretical physics problems, we bring into the game incredibly brilliant students, people who we want to attract to fusion development but who wouldn’t have an engineer’s excitement about new advances in technology.

    “And they will stay on because they see not just the applicability of fusion but also the intellectual challenge,” he says. “That’s key.”

    See the full article here .


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  • richardmitnick 12:50 pm on December 21, 2018 Permalink | Reply
    Tags: , , Fusion technology, , ,   

    From MIT News: “On the right path to fusion energy” 

    MIT News
    MIT Widget

    From MIT News

    December 21, 2018
    Peter Dunn

    1
    A fusion power plant could provide clean, carbon-free energy with an essentially unlimited fuel supply. From the point of view of electrical power generation, the fusion device is just another heat source that could be used in a conventional thermal conversion cycle. Image courtesy of PSFC, adapted from Wikimedia Commons.

    A new report on the development of fusion as an energy source, written at the request of the U.S. Secretary of Energy, proposes adoption of a national fusion strategy that closely aligns with the course charted in recent years by MIT’s Plasma Science and Fusion Center (PSFC) and privately funded Commonwealth Fusion Systems (CFS), a recent MIT spinout.

    Fusion technology has long held the promise of producing safe, abundant, carbon-free electricity, while struggling to overcome the daunting challenges of creating and harnessing fusion reactions to produce net energy gain. But the Consensus Study Report from the National Academies of Science, Engineering, and Medicine states that magnetic-confinement fusion technology (an MIT focus since the 1970s) is now “sufficiently advanced to propose a path to demonstrate fusion generated energy within the next several decades.”

    It recommends continued U.S. participation in the international ITER fusion facility project and “a national program of accompanying research and technology leading to the construction of a compact pilot plant that produces electricity from fusion at the lowest possible capital cost.”

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

    That approach (which the report says would require up to $200 million in additional annual funding for several decades) leverages opportunities presented by new-generation superconducting magnets, reactor materials, simulators, and other relevant technologies. Of particular emphasis from the committee is the advances in high-temperature superconducting magnets which can access higher fields and smaller machines. The report recommends a U.S. program to prove out high-field large-bore magnets. They are seen as enabling faster and less-costly cycles of learning and development than extremely large experiments like ITER, which will not come on line until 2025, while still benefitting from the knowledge that emerges from those programs.

    This smaller-faster-cheaper approach is embodied in the SPARC reactor concept, which was developed at the PSFC and forms the foundation of CFS’s aggressive effort to demonstrate energy-gain fusion by the mid-2020s and produce practical reactor designs by the early 2030s.

    MIT SPARC fusion reactor tokamak

    This approach is based on the similar conclusion that high-field high-temperature magnets represent a game-changing technology. A $30 million program between CFS and MIT to demonstrate the high-field large bore superconducting magnets is underway at MIT and is a key step to a compact fusion energy system. Despite a handful of other privately funded fusion companies having offered roughly comparable timelines, the National Academies report does not envision demonstration fusion reactors appearing until the 2050 time frame.

    The report also affirms that the scientific underpinnings of the tokamak approach have been strengthened over the previous decade, giving increasing confidence that this approach, which is the basis of ITER and SPARC, is capable of achieving net energy gain and forming the basis for a power plant. Based on this increased confidence the committee recommends moving forward with technology developments for a pilot power plant that would put power on the grid.

    “The National Academies are a very thoughtful organization, and they’re typically very conservative,” says Bob Mumgaard, chief executive officer of CFS. “We’re glad to see them come out with a message that it’s time to move into fusion, and that compact and economical is the way to go. We think development should go faster, but it gives validation to people who want to tackle the challenge and lays out things we can do in the U.S. that will lead toward putting power on the grid.”

    Andrew Holland, director of the recently formed Fusion Industry Association and Senior Fellow for Energy and Climate at the American Security Project, notes that the report’s authors were charged with creating “a consensus science report that reflects current pathways, and the current pathway is to build ITER and go through the experimental process there, while meanwhile designing a pilot plant, DEMO.”

    Shifting the consensus toward a faster way forward, adds Holland, will require experimental results from companies like CFS. “That’s why it’s notable to have privately funded companies in the U.S. and around the world pursuing the scientific results that will bear this out. And it’s certainly important that this study is aimed at getting the government-based science community to think about a strategic plan. It should be seen as part of a starting gun for the fusion community coming together and organizing its own process.”

    Or, as Martin Greenwald, deputy director of the PSFC and a veteran fusion researcher, puts it, “There’s a tendency in our community to argue about a 20-year plan or a 30-year plan, but we don’t want to take our eyes off what we need to do in the next three to five years. We might not have consensus on the long scale, but we need one for what to do now, and that’s been the consistent message since we announced the SPARC project — engaging the broader community and taking the initiative.

    “The key thing to us is that if fusion is going to have an impact on climate change, we need answers quickly, we can’t wait until the end of century, and that’s driving the schedule. The private money that’s coming in helps, but public funding should engage with and complement that. Each side has an appropriate role. National labs don’t build power plants, and private companies don’t do basic research.”

    While several approaches to fusion are being pursued in public and private organizations, the National Academies report focuses exclusively on magnetic confinement technology. This reflects the report’s role in the Department of Energy’s response to a 2016 Congressional request for information on U.S. participation in ITER, a magnetic-confinement project. The report committee’s 19 experts, who conducted two years of research, were also charged with exploring related questions of “how best to advance the fusion sciences in the U.S.” and “the scientific justification and needs for strengthening the foundations for realizing fusion energy given a potential choice of U.S. participation or not in the ITER project.”

    The report’s publication comes at a time of renewed activity and interest in fusion energy, with some 20 private companies pursuing its development, increased funding in the most recent federal budget, and the formation of the Fusion Industry Association to advocate for the community as a whole. But the report cautions that “the absence of a long-term research strategy for the United States is particularly evident when compared to the plans of our international partners.”

    That situation may be evolving. “We had a very nice meeting of stakeholders a month and a half ago in DC, and there was a lot of resonance among private companies, the research community, the Department of Energy, and Congressional staffers from both parties,” says Greenwald. “It seems like there’s momentum, though we don’t know yet just what form it will take.” He adds that the establishment of an industry association is very helpful for navigating and communicating in Washington.

    “We would love to see the government have a role in things that lift all fusion companies, like advanced materials labs, the process of extracting heat from reactors, additive manufacturing, simulations, and other tools,” says Mumgaard. “There are many opportunities for collaboration and cooperation; every company will have a different mix of partnerships, even on personnel exchange as we do with MIT.”

    See the full article here .


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  • richardmitnick 11:22 am on October 22, 2018 Permalink | Reply
    Tags: , Fusion technology, ,   

    From Medium: “Fusion Power, or Creating A Star On Earth” 

    From Medium

    Oct 20, 2018
    Ella Alderson

    1
    In this image, an accelerator shot brightens up the surface of the Z Machine in New Mexico. It’s the world’s most powerful source of laboratory radiation and holds the energy equivalent of up to 52 sticks of dynamite. Researchers at the Sandia National Laboratory hope to find an alternative approach to fusion power.

    Sandia Z machine

    Energy production today is a battlefield. It’s a competition between the grime and pollution of fossil fuels, the unreliability of solar and wind power, and the looming towers of nuclear plants and their dangerous waste. With the world’s energy consumption growing each year and the planet straining under our use of coal and oil, an innovative source of energy for our cities is quickly becoming a necessity. That’s what makes fusion power so attractive; it promises to provide all the energy we need reliably, cheaply, and, most exciting of all, in an environmentally safe way with zero carbon emissions. It would be the ultimate source of power for our booming civilizations here on Earth and our craft setting out to explore the solar system. Even catastrophes at a fusion reactor would result in little more than the plasma expanding and cooling, with no chances of a huge, endangering explosion.

    And it’s not impossible. Fusion is what drives every star dotting the endless skies — including our gorgeous, broiling sun. At its core, hydrogen is fused into helium and eventually escapes as electromagnetic radiation. That is, two hydrogen atoms are rammed together and produce a helium atom as a result. But the fusion of one element into another is not as easy as it sounds. Because both protons have the same charge, the only way to overcome their natural repellence is to bring them close enough together that they fuse. The sun is able to do this because of its immense mass (it claims 99.8% of all matter in our solar system) and, consequently, the immense amount of gravitational force made available. The heat, the pressure, and the gravity are what make solar fusion possible.

    That’s what makes fusion different from fission — while fission aims to split apart a heavier nucleus into two lighter ones, fusion brings together lighter nuclei into a heavier one. The fusion process means the resulting element has less mass and the remaining mass turns into energy. An enormous amount of energy. Our nuclear reactors today use fission, which unfortunately makes radioactive waste that lasts tens of thousands of years. Still, many see fission powered reactors as an improvement over fossil fuels since it’s less polluting than most other sources of energy and has helped us avoid 14 billion metric tons of carbon dioxide in the past 21 years. Nuclear power is affordable and provides about 20% of all electricity in the US.

    But it’s not fusion. It’s not everything fusion promises to be.

    2
    Oil from an explosion mars the waters of the Gulf of Mexico. Fusion energy could provide the same amount of power from a single glass of seawater as burning an entire barrel of oil. Hydrogen isotopes extracted from the seawater would provide limitless power. Image by Kari Goodnough.

    But it turns out recreating conditions of the sun here on Earth isn’t going to be a straightforward task. One of the saddest jokes regarding fusion is that it’s the energy of the future…and always will be. This type of remarkable energy has been 30 years away for the past 8 decades now. But this time could be different. Physicists are feeling more confident than ever in their ability to problem-solve and there’s been a great number of breakthroughs in the last few years.

    One of the problems they face is that the process requires temperatures in the hundreds of millions of degrees — temperatures up to 10 times higher than those at the core of the sun. Needless to say, no solid material could withstand that amount of heat and so scientists often use magnetic fields to hold up the scorching plasma during what’s known as magnetic confinement. Magnets then press the plasma into higher densities, but that means the atoms aren’t always stable enough to contain the energy. Plasma heated using lasers and ion beams require too much energy going into the system.

    In short, the current goal of fusion research is to break even in terms of energy. Researchers want to get as much energy out as what they’re putting in. Up until now we’ve been working on a deficit where energy output is far less than energy input. The end goal, of course, is to get many times as much energy out as what we’re putting in.

    Some new approaches are a hybrid of electrical and magnetic fields that beam atoms against a solid target until the atoms from the beam fuse together with those of the target. This process utilizes hydrogen since lighter elements produce more energy during fusion. The trick here is to minimize the number of atoms scattering and thus increase the amount of energy collected.

    As far as a commercial reach for fusion goes, estimates range from 60 years from today to a mere 15 depending on who you ask. Researchers from MIT are confident they can have a fusion reactor on the grid as soon as 2033, though even that brings up the question of whether or not we can afford to wait so long for clean energy.

    3
    The Joint European Torus is the world’s largest and most powerful tokamak — a machine that confines hot plasma into the shape of a torus by use of a magnetic field.

    Instead of focusing too much on the technicalities of fusion power itself, I was very interested in what this kind of energy would mean for space exploration. It turns out that NASA is funding a fusion-powered rocket with hopes of a working prototype by 2020. If successful, fusion powered spacecraft would reach Mars twice as fast as anything we could send now. This means that instead of a trip to the red planet taking 7 months, it would only take a little over 3, greatly reducing the crew’s exposure to radiation, psychological strain, and weightlessness. Not to mention they would need much less food, fuel, and oxygen onboard. In fact, a small grain of aluminum would provide the equivalent power as a gallon of fuel does in today’s chemical rockets.

    Fusion rockets would have a specific impulse of 130,000 seconds — 300 times greater than that of modern rockets. Specific impulse is a term that refers to the relationship between thrust and the amount of propellant used. In the case of chemical rockets, a specific impulse of 450 seconds means that a rocket can hold 1 pound of thrust from 1 pound of fuel for about 450 seconds. Fusion rockets would also allow for a bigger payload since not as much room is needed for fuel. Instead, magnets with lithium bands would push atoms together, resulting in fusion and energy to push the rocket forward. If the fusion rockets use hydrogen as a propellant, they could replenish their stock by collecting hydrogen from the surface of planets.

    It’s a fast, much more efficient method of interplanetary travel. And the foundations for it are being built today. Projects like VASIMR act as steps on the path to fusion rockets. VASIMR is a plasma rocket that heats and expels the plasma to create thrust but, because fusion rockets will also use plasma, anything researchers can learn from this craft would help them in the design and creation of a fusion drive.

    Recreating the power of a star is something that sounds uniquely human: a violent, tricky, seemingly fantastical goal. And yet achieving it would bring our civilization so much, both in terms of physical energy and introspection. How far can we truly advance, and can we reach the goals of our wildest ambitions?

    See the full article here .

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    Medium is an online publishing platform developed by Evan Williams, and launched in August 2012. It is owned by A Medium Corporation. The platform is an example of social journalism, having a hybrid collection of amateur and professional people and publications, or exclusive blogs or publishers on Medium, and is regularly regarded as a blog host.

    Williams developed Medium as a way to publish writings and documents longer than Twitter’s 140-character (now 280-character) maximum.

     
  • richardmitnick 7:21 pm on October 16, 2018 Permalink | Reply
    Tags: , Fusion technology, , , MIT Plasma Science and Fusion Center, Nuno Loureiro, Physicist explores the behavior of the universe’s most abundant form of matter, Physics of plasmas, Plasma is a sort of fourth phase of matter, The solar wind is the best plasma turbulence laboratory we have, Turbulence-a major stumbling block so far to practical fusion power   

    From MIT News-“Nuno Loureiro: Probing the world of plasmas” 

    MIT News
    MIT Widget

    From MIT News

    October 15, 2018
    David L. Chandler

    1
    A major motivation for moving to MIT from his research position, Nuno Loureiro says, was working with students. Image: Jared Charney

    Physicist explores the behavior of the universe’s most abundant form of matter.

    Growing up in the small city of Viseu in central Portugal, Nuno Loureiro knew he wanted to be a scientist, even in the early years of primary school when “everyone else wanted to be a policeman or a fireman,” he recalls. He can’t quite place the origin of that interest in science: He was 17 the first time he met a scientist, he says with an amused look.

    By the time Loureiro finished high school, his interest in science had crystallized, and “I realized that physics was what I liked best,” he says. During his undergraduate studies at the IST Lisbon, he began to focus on fusion, which “seemed like a very appealing field,” where major developments were likely during his lifetime, he says.

    Fusion, and specifically the physics of plasmas, has remained his primary research focus ever since, through graduate school, postdoc stints, and now in his research and teaching at MIT. He explains that plasma research “lives in two different worlds.” On the one hand, it involves astrophysics, dealing with the processes that happen in and around stars; on the other, it’s part of the quest to generate electricity that’s clean and virtually inexhaustible, through fusion reactors.

    Plasma is a sort of fourth phase of matter, similar to a gas but with the atoms stripped apart into a kind of soup of electrons and ions. It forms about 99 percent of the visible matter in the universe, including stars and the wispy tendrils of material spread between them. Among the trickiest challenges to understanding the behavior of plasmas is their turbulence, which can dissipate away energy from a reactor, and which proceeds in very complex and hard-to-predict ways — a major stumbling block so far to practical fusion power.

    While everyone is familiar with turbulence in fluids, from breaking waves to cream stirred into coffee, plasma turbulence can be quite different, Loureiro explains, because plasmas are riddled with magnetic and electric fields that push and pull them in dynamic ways. “A very noteworthy example is the solar wind,” he says, referring to the ongoing but highly variable stream of particles ejected by the sun and sweeping past Earth, sometimes producing auroras and affecting the electronics of communications satellites. Predicting the dynamics of such flows is a major goal of plasma research.

    “The solar wind is the best plasma turbulence laboratory we have,” Loureiro says. “It’s increasingly well-diagnosed, because we have these satellites up there. So we can use it to benchmark our theoretical understanding.”

    Loureiro began concentrating on plasma physics in graduate school at Imperial College London and continued this work as a postdoc at the Princeton Plasma Physics Laboratory and later the Culham Centre for Fusion Energy, the U.K.’s national fusion lab. Then, after a few years as a principal researcher at the University of Portugal, he joined the MIT faculty at the Plasma Science and Fusion Center in 2016 and earned tenure in 2017. A major motivation for moving to MIT from his research position, he says, was working with students. “I like to teach,” he says. Another was the “peerless intellectual caliber of the Plasma Science and Fusion Center at MIT.”

    Loureiro, who holds a joint appointment in MIT’s Department of Physics, is an expert on a fundamental plasma process called magnetic reconnection. One example of this process occurs in the sun’s corona, a glowing irregular ring that surrounds the disk of the sun and becomes visible from Earth during solar eclipses. The corona is populated by vast loops of magnetic fields, which buoyantly rise from the solar interior and protrude through the solar surface. Sometimes these magnetic fields become unstable and explosively reconfigure, unleashing a burst of energy as a solar flare. “That’s magnetic reconnection in action,” he says.

    Over the last couple of years at MIT, Loureiro published a series of papers with physicist Stanislav Boldyrev at the University of Wisconsin, in which they proposed a new analytical model to reconcile critical disparities between models of plasma turbulence and models of magnetic reconnection. It’s too early to say if the new model is correct, he says, but “our work prompted a reanalysis of solar wind data and also new numerical simulations. The results from these look very encouraging.”

    Their new model, if proven, shows that magnetic reconnection must play a crucial role in the dynamics of plasma turbulence over a significant range of spatial scales – an insight that Loureiro and Boldyrev claim would have profound implications.

    Loureiro says that a deep, detailed understanding of turbulence and reconnection in plasmas is essential for solving a variety of thorny problems in physics, including the way the sun’s corona gets heated, the properties of accretion disks around black holes, nuclear fusion, and more. And so he plugs away, to continue trying to unravel the complexities of plasma behavior. “These problems present beautiful intellectual challenges,” he muses. “That, in itself, makes the challenge worthwhile. But let’s also keep in mind that the practical implications of understanding plasma behavior are enormous.”

    See the full article here .


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  • richardmitnick 9:33 am on October 10, 2018 Permalink | Reply
    Tags: , Fusion technology, , , ,   

    From MIT: “A new path to solving a longstanding fusion challenge” 

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    From MIT News

    October 9, 2018
    David L. Chandler

    1
    The ARC conceptual design for a compact, high magnetic field fusion power plant. The design now incorporates innovations from the newly published research to handle heat exhaust from the plasma. ARC rendering by Alexander Creely

    2
    The ARC conceptual design for a compact, high magnetic field fusion power plant. Numbered components are as follows: 1. plasma; 2. The newly designed divertor; 3. copper trim coils; 4. High-temperature superconductor (HTS) poloidal field coils, used to shape the plasma in the divertor; 5. FLiBe blanket, a liquid material that collects heat from emitted neutrons; 6. HTS toroidal field coils, which shape the main plasma torus; 7. HTS central solenoid; 8. vacuum vessel; 9. FLiBe tank; 10. joints in toroidal field coils, which can be opened to allow for access to the interior. ARC rendering by Alexander Creely

    Novel design could help shed excess heat in next-generation fusion power plants.

    A class exercise at MIT, aided by industry researchers, has led to an innovative solution to one of the longstanding challenges facing the development of practical fusion power plants: how to get rid of excess heat that would cause structural damage to the plant.

    The new solution was made possible by an innovative approach to compact fusion reactors, using high-temperature superconducting magnets. This method formed the basis for a massive new research program launched this year at MIT and the creation of an independent startup company to develop the concept. The new design, unlike that of typical fusion plants, would make it possible to open the device’s internal chamber and replace critical comonents; this capability is essential for the newly proposed heat-draining mechanism.

    The new approach is detailed in a paper in the journal Fusion Engineering and Design, authored by Adam Kuang, a graduate student from that class, along with 14 other MIT students, engineers from Mitsubishi Electric Research Laboratories and Commonwealth Fusion Systems, and Professor Dennis Whyte, director of MIT’s Plasma Science and Fusion Center, who taught the class.

    In essence, Whyte explains, the shedding of heat from inside a fusion plant can be compared to the exhaust system in a car. In the new design, the “exhaust pipe” is much longer and wider than is possible in any of today’s fusion designs, making it much more effective at shedding the unwanted heat. But the engineering needed to make that possible required a great deal of complex analysis and the evaluation of many dozens of possible design alternatives.

    Taming fusion plasma

    Fusion harnesses the reaction that powers the sun itself, holding the promise of eventually producing clean, abundant electricity using a fuel derived from seawater — deuterium, a heavy form of hydrogen, and lithium — so the fuel supply is essentially limitless. But decades of research toward such power-producing plants have still not led to a device that produces as much power as it consumes, much less one that actually produces a net energy output.

    Earlier this year, however, MIT’s proposal for a new kind of fusion plant — along with several other innovative designs being explored by others — finally made the goal of practical fusion power seem within reach.

    MIT SPARC fusion reactor tokamak

    But several design challenges remain to be solved, including an effective way of shedding the internal heat from the super-hot, electrically charged material, called plasma, confined inside the device.

    Most of the energy produced inside a fusion reactor is emitted in the form of neutrons, which heat a material surrounding the fusing plasma, called a blanket. In a power-producing plant, that heated blanket would in turn be used to drive a generating turbine. But about 20 percent of the energy is produced in the form of heat in the plasma itself, which somehow must be dissipated to prevent it from melting the materials that form the chamber.

    No material is strong enough to withstand the heat of the plasma inside a fusion device, which reaches temperatures of millions of degrees, so the plasma is held in place by powerful magnets that prevent it from ever coming into direct contact with the interior walls of the donut-shaped fusion chamber. In typical fusion designs, a separate set of magnets is used to create a sort of side chamber to drain off excess heat, but these so-called divertors are insufficient for the high heat in the new, compact plant.

    One of the desirable features of the ARC design is that it would produce power in a much smaller device than would be required from a conventional reactor of the same output. But that means more power confined in a smaller space, and thus more heat to get rid of.

    “If we didn’t do anything about the heat exhaust, the mechanism would tear itself apart,” says Kuang, who is the lead author of the paper, describing the challenge the team addressed — and ultimately solved.

    Inside job

    In conventional fusion reactor designs, the secondary magnetic coils that create the divertor lie outside the primary ones, because there is simply no way to put these coils inside the solid primary coils. That means the secondary coils need to be large and powerful, to make their fields penetrate the chamber, and as a result they are not very precise in how they control the plasma shape.

    But the new MIT-originated design, known as ARC (for advanced, robust, and compact) features magnets built in sections so they can be removed for service. This makes it possible to access the entire interior and place the secondary magnets inside the main coils instead of outside. With this new arrangement, “just by moving them closer [to the plasma] they can be significantly reduced in size,” says Kuang.

    In the one-semester graduate class 22.63 (Principles of Fusion Engineering), students were divided into teams to address different aspects of the heat rejection challenge. Each team began by doing a thorough literature search to see what concepts had already been tried, then they brainstormed to come up with multiple concepts and gradually eliminated those that didn’t pan out. Those that had promise were subjected to detailed calculations and simulations, based, in part, on data from decades of research on research fusion devices such as MIT’s Alcator C-Mod, which was retired two years ago. C-Mod scientist Brian LaBombard also shared insights on new kinds of divertors, and two engineers from Mitsubishi worked with the team as well. Several of the students continued working on the project after the class ended, ultimately leading to the solution described in this new paper. The simulations demonstrated the effectiveness of the new design they settled on.

    “It was really exciting, what we discovered,” Whyte says. The result is divertors that are longer and larger, and that keep the plasma more precisely controlled. As a result, they can handle the expected intense heat loads.

    “You want to make the ‘exhaust pipe’ as large as possible,” Whyte says, explaining that the placement of the secondary magnets inside the primary ones makes that possible. “It’s really a revolution for a power plant design,” he says. Not only do the high-temperature superconductors used in the ARC design’s magnets enable a compact, high-powered power plant, he says, “but they also provide a lot of options” for optimizing the design in different ways — including, it turns out, this new divertor design.

    Going forward, now that the basic concept has been developed, there is plenty of room for further development and optimization, including the exact shape and placement of these secondary magnets, the team says. The researchers are working on further developing the details of the design.

    “This is opening up new paths in thinking about divertors and heat management in a fusion device,” Whyte says.

    “All of the ARC work has been both eye-opening and stimulating of new ways of looking at tokamak fusion reactors,” says Bruce Lipschultz, a professor of physics at the University of York, in the U.K., who was not involved in this work. This latest paper, he says, “incorporates new ideas in the field with the many other significant improvements in the tokamak concept. … The ARC study of the extended leg divertor concept shows that the application to a reactor is not impossible, as others have contended.”

    Lipschultz adds that this is “very high-quality research that shows a way forward for the tokamak reactor and stimulates new research elsewhere.”

    The team included MIT graduate students Norman Cao, Alexander Creely, Cody Dennett, Jake Hecla, Brian LaBombard, Roy Tinguely, Elizabeth Tolman, H. Hoffman, Maximillian Major, Juan Ruiz Ruiz, Daniel Brunner, and Brian Sorbom, and Mitsubishi Electric Research Laboratories engineers P. Grover and C. Laughman. The work was supported by MIT’s Department of Nuclear Science and Engineering, the Department of Energy, the National Science Foundation, and Mitsubishi Electric Research Laboratories.

    See the full article here .


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  • richardmitnick 10:42 pm on October 2, 2018 Permalink | Reply
    Tags: , , , Fusion technology, , , ,   

    From SLAC National Accelerator Lab: “Peering into 36-million-degree plasma with SLAC’s X-ray laser” 

    From SLAC National Accelerator Lab

    October 2, 2018
    Ali Sundermier
    For commnication
    communications@slac.stanford.edu

    1
    At the Matter in Extreme Conditions (MEC) instrument at LCLS, the researchers zapped knuckle-shaped samples with a laser to create plasma, then used an X-ray scattering technique to watch it expand and collide. (Matt Beardsley/SLAC National Accelerator Laboratory)

    When you hit a piece of metal with a strong enough laser pulse you get a plasma – a hot, ionized gas found in everything from lightning to the sun. Studying it helps scientists understand what’s going on inside stars and could enable new types of particle accelerators for cancer treatment.

    Now a team of researchers has used an X-ray laser to measure, for the first time, how a plasma created by a laser blast expands in the hundreds of femtoseconds (quadrillionths of a second) after it’s created. Their technique could eventually reveal tiny instabilities in the plasma that swirl like cream in a cup of coffee.

    The experiments at the Department of Energy’s SLAC National Accelerator Laboratory involved scientists from SLAC, German research center Helmholtz-Zentrum Dresden-Rossendorf (HZDR) and other institutions, and was reported in Physical Review X in September.

    Blasting cancer cells

    Led by scientist Thomas Kluge at HZDR, the researchers have been working to harness the behavior of plasma to create a new type of particle accelerator for proton therapy, an existing cancer treatment that involves blasting tumors with charged particles rather than X-rays. This approach is gentler on the surrounding healthy tissue than traditional radiation therapy.

    When solid matter is zapped with a laser the interaction forms a plasma, causing a steady stream of protons to burst out of the back side of the sample. The researchers hope to use the proton streams to storm tumors and obliterate cancer cells. But producing these fast protons in a reliable way requires a better understanding of how plasma changes as it expands.

    “Instabilities can arise from the complex streams of electrons and ions moving back and forth in the plasma,” Kluge says. “You probably know one of these instabilities from the mushroom-shaped clouds that form when you drip milk into your morning coffee.”

    Hotter than ever

    Until now, it was difficult to probe plasma changes directly because they’re so tiny and happen on extremely fast time scales. This work, says Josefine Metzkes-Ng, co-author and junior group leader at HZDR, could only be done at SLAC where the researchers used a high-power, short-pulse optical laser beam to create the plasma and the Linac Coherent Light Source X-ray free-electron laser to probe it.

    SLAC/LCLS

    At the Matter in Extreme Conditions (MEC) instrument at LCLS, researchers create incredibly hot and dense matter that mimics the extreme conditions in the hearts of stars and planets. Simulations show that the researchers achieved a new temperature record for matter studied with a free-electron laser: 36 million degrees Fahrenheit, almost 10 million degrees hotter than the sun’s core.

    The researchers fabricated solid samples that consisted of raised silicon bars, like knuckles sticking out from a fist. They found that in the quadrillionths of seconds after they zapped the sample with intense, short pulses from the optical laser, tiny amounts of plasma stacked up between the knuckles. A special form of scattering that uses X-ray pulses from LCLS allowed them to peer inside the plasma to follow its evolution.

    This technique will pave the way for better understanding plasma instabilities, allowing researchers to create proton sources for cancer therapy with relatively small footprints that, unlike conventional accelerators, can be operated within a hospital. It will also be useful in research relevant to fusion energy, other types of novel particle accelerators and laboratory astrophysics.

    Speedy cosmic particles

    Siegfried Glenzer, director of the High Energy Density Division at SLAC, who helped with the paper, is especially excited about the prospect of using this technique to better understand the astrophysical processes that give cosmic rays – subatomic space particles that plunge into Earth’s atmosphere at almost the speed of light – their extreme energies.

    The highest-energy cosmic rays can pack a force comparable to that of a major league fastball hurtling toward a batter at 100 mph, condensed into a single subatomic particle. To accelerate a proton to the same energies as these cosmic rays, scientists would have to build an accelerator that sends particles traveling from Earth to Saturn and back.

    Using LCLS, scientists are able to recreate some of the astrophysical processes that may produce these high-energy cosmic rays, such as energetic jets that shoot out from the turbulent hearts of active galaxies. Now the new technique will allow them to directly observe the plasma instabilities that might be responsible for accelerating cosmic rays.

    “Cosmic rays are the largest particle accelerators known to mankind,” Glenzer says. “They have a million times higher energy than particles accelerated in the Large Hadron Collider. Recently, astronomers traced a cosmic ray particle to an active galactic nucleus jet. Our goal is to produce these types of jets in the laboratory so we can study the formation of these instabilities and show whether they can accelerate particles to such high energies and, if so, how it happens.”

    Flipping the light switch

    According to Kluge, “This research has opened the black box of how short-pulse lasers interact with solids, allowing us to directly see a little of what’s going on, which previously could only be simulated with largely unverified atomic models.

    “It’s a little like switching on a light,” he says. “Although we have some ideas, we don’t know what we will find, but surely it will help us develop the next generation of laser-based ion accelerators and could shape new applications in astrophysics, medicine and plasma physics. For me as a theorist and simulation guy, the most exciting thing about this project is that I can now lay my simulations aside and look at the real thing.”

    The research team also included scientists from Technical University Dresden, European XFEL, University of Siegen, Friedrich Schiller University Jena and Leibniz Institute of Photonic Technology, all in Germany.

    LCLS is a DOE Office of Science user facility. Funding was provided by the DOE Office of Science.

    See the full article here .


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    SLAC is a multi-program laboratory exploring frontier questions in photon science, astrophysics, particle physics and accelerator research. Located in Menlo Park, California, SLAC is operated by Stanford University for the DOE’s Office of Science.

     
  • richardmitnick 11:24 am on September 22, 2018 Permalink | Reply
    Tags: , Fusion technology, ,   

    From U Tokyo via ScienceAlert: “Scientists Just Created a Magnetic Field That Takes Us Closer Than Ever Before to Harnessing Nuclear Fusion” 

    From University of Tokyo

    via

    ScienceAlert

    1
    (Zoltan Tasi/Unsplash)

    22 SEP 2018
    KRISTIN HOUSER

    They were able to control it without destroying any equipment this time.

    Inexpensive clean energy sounds like a pipe dream. Scientists have long thought that nuclear fusion, the type of reaction that powers stars like the Sun, could be one way to make it happen, but the reaction has been too difficult to maintain.

    Now, we’re closer than ever before to making it happen — physicists from the University of Tokyo (UTokyo) say they’ve produced the strongest-ever controllable magnetic field.

    “One way to produce fusion power is to confine plasma — a sea of charged particles — in a large ring called a tokamak in order to extract energy from it,” said lead researcher Shojiro Takeyama in a press release.

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

    September 18, 2018

    Physicists from the Institute for Solid State Physics at the University of Tokyo have generated the strongest controllable magnetic field ever produced. The field was sustained for longer than any previous field of a similar strength. This research could lead to powerful investigative tools for material scientists and may have applications in fusion power generation.

    Magnetic fields are everywhere. From particle smashers to the humble compass, our capacity to understand and control these fields crafted much of the modern world. The ability to create stronger fields advances many areas of science and engineering. UTokyo physicist Shojiro Takeyama and his team created a large sophisticated device in a purpose-built lab, capable of producing the strongest controllable magnetic field ever using a method known as electromagnetic flux compression.

    “Decades of work, dozens of iterations and a long line of researchers who came before me all contributed towards our achievement,” said Professor Takeyama. “I felt humbled when I was personally congratulated by directors of magnetic field research institutions around the world.”

    Physicists from the Institute for Solid State Physics at the University of Tokyo have generated the strongest controllable magnetic field ever produced. The field was sustained for longer than any previous field of a similar strength. This research could lead to powerful investigative tools for material scientists and may have applications in fusion power generation.

    Magnetic fields are everywhere. From particle smashers to the humble compass, our capacity to understand and control these fields crafted much of the modern world. The ability to create stronger fields advances many areas of science and engineering. UTokyo physicist Shojiro Takeyama and his team created a large sophisticated device in a purpose-built lab, capable of producing the strongest controllable magnetic field ever using a method known as electromagnetic flux compression.

    “Decades of work, dozens of iterations and a long line of researchers who came before me all contributed towards our achievement,” said Professor Takeyama. “I felt humbled when I was personally congratulated by directors of magnetic field research institutions around the world.”

    2
    The megagauss generator just before it’s switched on. Some parts for the device are exceedingly rare and very few companies around the world are capable of producing them. Image: ©2018 Shojiro Takeyama

    3
    Sparks fly at the moment of activation. Four million amps of current feed the megagauss generator system, hundreds of times the current of a typical lightning bolt. Image: ©2018 Shojiro Takeyama

    But what is so interesting about this particular magnetic field?

    At 1,200 teslas – not the brand of electric cars, but the unit of magnetic field strength – the generated field dwarfs almost any artificial magnetic field ever recorded; however, it’s not the strongest overall. In 2001, physicists in Russia produced a field of 2,800 teslas, but their explosive method literally blew up their equipment and the uncontrollable field could not be tamed. Lasers can also create powerful magnetic fields, but in experiments they only last a matter of nanoseconds.

    The magnetic field created by Takeyama’s team lasts thousands of times longer, around 100 microseconds, about one-thousandth of the time it takes to blink. It’s possible to create longer-lasting fields, but these are only in the region of hundreds of teslas. The goal to surpass 1,000 teslas was not just a race for the sake of it, that figure represents a significant milestone.

    4
    Earth’s own magnetic field is 25 to 65 microteslas. The megagauss generator system creates a field of 1,200 teslas, about 20 million to 50 million times stronger. Image: ©2018 Shojiro Takeyama

    “With magnetic fields above 1,000 Teslas, you open up some interesting possibilities,” says Takeyama. “You can observe the motion of electrons outside the material environments they are normally within. So we can study them in a whole new light and explore new kinds of electronic devices. This research could also be useful to those working on fusion power generation.”

    This is an important point, as many believe fusion power is the most promising way to provide clean energy for future generations. “One way to produce fusion power is to confine plasma – a sea of charged particles – in a large ring called a tokamak in order to extract energy from it,” explains Takeyama. “This requires a strong magnetic field in the order of thousands of teslas for a duration of several microseconds. This is tantalizingly similar to what our device can produce.”

    The magnetic field that a tokamak would require is “tantalizingly similar to what our device can produce,” he said.

    To generate the magnetic field, the UTokyo researchers built a sophisticated device capable of electromagnetic flux-compression (EMFC), a method of magnetic field generation well-suited for indoor operations.

    They describe the work in a new paper published Monday in the Review of Scientific Instruments.

    Using the device, they were able to produce a magnetic field of 1,200 teslas — about 120,000 times as strong as a magnet that sticks to your refrigerator.

    Though not the strongest field ever created, the physicists were able to sustain it for 100 microseconds, thousands of times longer than previous attempts.

    They could also control the magnetic field, so it didn’t destroy their equipment like some past attempts to create powerful fields.

    As Takeyama noted in the press release, that means his team’s device can generate close to the minimum magnetic field strength and duration needed for stable nuclear fusion — and it puts us all one step closer to the unlimited clean energy we’ve been dreaming about for nearly a century.

    See the full article here .

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  • richardmitnick 4:40 pm on August 24, 2018 Permalink | Reply
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    From MIT: “Pushing the plasma density limit” 

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    From MIT News

    1
    Seung Gyou Baek and his colleagues performed experiments on the Alcator C-Mod tokamak to demonstrate how microwaves can be used to overcome barriers to steady-state fusion reactor operation. Photo: Paul Rivenberg/PSFC

    August 23, 2018
    Paul Rivenberg | Plasma Science and Fusion Center

    For decades, researchers have been exploring ways to replicate on Earth the physical process of fusion that occurs naturally in the sun and other stars. Confined by its own strong gravitational field, the sun’s burning plasma is a sphere of fusing particles, producing the heat and light that makes life possible on earth. But the path to a creating a commercially viable fusion reactor, which would provide the world with a virtually endless source of clean energy, is filled with challenges.

    Researchers have focused on the tokamak, a device that heats and confines turbulent plasma fuel in a donut-shaped chamber long enough to create fusion. Because plasma responds to magnetic fields, the torus is wrapped in magnets, which guide the fusing plasma particles around the toroidal chamber and away from the walls. Tokamaks have been able to sustain these reactions only in short pulses. To be a practical source of energy, they will need to operate in a steady state, around the clock.

    Researchers at MIT’s Plasma Science and Fusion Center (PSFC) have now demonstrated how microwaves can be used to overcome barriers to steady-state tokamak operation. In experiments performed on MIT’s Alcator C-Mod tokamak before it ended operation in September 2016, research scientist Seung Gyou Baek and his colleagues studied a method of driving current to heat the plasma called Lower Hybrid Current Drive (LHCD).

    Alcator C-Mod tokamak at MIT, no longer in operation

    The technique generates plasma current by launching microwaves into the tokamak, pushing the electrons in one direction — a prerequisite for steady-state operation.

    Furthermore, the strength of the Alcator magnets has allowed researchers to investigate LHCD at a plasma density high enough to be relevant for a fusion reactor. The encouraging results of their experiments have been published in Physical Review Letters.

    Pioneering LHCD

    “The conventional way of running a tokamak uses a central solenoid to drive the current inductively,” Baek says, referring to the magnetic coil that fills the center of the torus. “But that inherently restricts the duration of the tokamak pulse, which in turn limits the ability to scale the tokamak into a steady-state power reactor.”

    Baek and his colleagues believe LHCD is the solution to this problem.

    MIT scientists have pioneered LHCD since the 1970s, using a series of “Alcator” tokamaks known for their compact size and high magnetic fields. On Alcator C-Mod, LHCD was found to be efficient for driving currents at low density, demonstrating plasma current could be sustained non-inductively. However, researchers discovered that as they raised the density in these experiments to the higher levels necessary for steady-state operation, the effectiveness of LHCD to generate plasma current disappeared.

    This fall-off in effectiveness as density increased was first studied on Alcator C-Mod by research scientist Gregory Wallace.

    “He measured the fall-off to be much faster than expected, which was not predicted by theory,” Baek explains. “The last decade people have been trying to understand this, because unless this problem is solved you can’t really use this in a reactor.”

    Researchers needed to find a way to boost effectiveness and overcome the LHCD density limit. Finding the answer would require a close examination of how lower hybrid (LH) waves respond to the tokamak environment.

    Driving the current

    Lower hybrid waves drive plasma current by transferring their momentum and energy to electrons in the plasma.

    Head of the PSFC’s Physics Theory and Computation Division, senior research scientist Paul Bonoli compares the process to surfing.

    “You are on a surf board and you have a wave come by. If you just sit there the wave will kind of go by you,” Bonoli says. “But if you start paddling, and you get near the same speed as the wave, the wave picks you up and starts transferring energy to the surf board. Well, if you inject radio waves, like LH waves, that are moving at velocities near the speed of the particles in the plasma, the waves start to give up their energy to these particles.”

    Temperatures in today’s tokamaks — including C-Mod — are not high enough to provide good matching conditions for the wave to transfer all its momentum to the plasma particles on the first pass from the antenna, which launches the waves to the core plasma. Consequently, researchers noticed, the injected microwave travels through the core of the plasma and beyond, eventually interacting multiple times with the edge, where its power dissipates, particularly when the density is high.

    Exploring the scrape-off layer

    Baek describes this edge as a boundary area outside the main core of the plasma where, in order to control the plasma, researchers can drain — or “scrape-off” — heat, particles, and impurities through a divertor. This edge has turbulence, which, at higher densities, interacts with the injected microwaves, scattering them, and dissipating their energy.

    “The scrape-off layer is a very thin region. In the past RF scientists didn’t really pay attention to it,” Baek says. “Our experiments have shown in the last several years that interaction there can be really important in understanding the problem, and by controlling it properly you can overcome the density limit problem.”

    Baek credits extensive simulations by Wallace and PSFC research scientist Syun’ichi Shiraiwa for indicating that the scrape-off layer was most likely the location where LH wave power was being lost.

    Detailed research on the edge and scrape-off-layer conducted on Alcator C-Mod in the last two decades has documented that raising the total electrical current in the plasma narrows the width of the scrape-off-layer and reduces the level of turbulence there, suggesting that it may reduce or eliminate its deleterious effects on the microwaves.

    Motivated by this, PSFC researchers devised an LHCD experiment to push the total current by from 500,000 Amps to 1,400,000 Amps, enabled by C-Mod’s high-field tokamak operation. They found that the effectiveness of LCHD to generate plasma current, which had been lost at high density, reappeared. Making the width of the turbulent scrape-off layer very narrow prevents it from dissipating the microwaves, allowing higher densities to be reached beyond the LHCD density limit.

    The results from these experiments suggest a path to a steady-state fusion reactor. Baek believes they also provide additional experimental support to proposals by the PSFC to place the LHCD antenna at the high-field (inboard) side of a tokamak, near the central solenoid. Research suggests that placing it in this quiet area, as opposed to the turbulent outer midplane, would minimize destructive wave interactions in the plasma edge, while protecting the antenna and increasing its effectiveness. Principal Research scientist Steven Wukitch is currently pursuing new LHCD research in this area through PSFCs’ collaboration with the DIII-D tokamak in San Diego.

    Although existing tokamaks with LHCD are not operating at the high densities of C-Mod, Baek feels that the relationship between the current drive and the scrape-off layer could be investigated on any tokamak.

    “I hope our recipe for improving LHCD performance will be explored on other machines, and that these results invigorate further research toward steady-state tokamak operation,” he says.

    See the full article here .


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