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  • richardmitnick 9:19 am on August 26, 2015 Permalink | Reply
    Tags: , , Fusion technology   

    From AAAS: “Exclusive: Secretive fusion company claims reactor breakthrough” 

    AAAS

    AAAS

    24 August 2015
    Daniel Clery


    Download .mp4 here.

    In a suburban industrial park south of Los Angeles, researchers have taken a significant step toward mastering nuclear fusion—a process that could provide abundant, cheap, and clean energy. A privately funded company called Tri Alpha Energy has built a machine that forms a ball of superheated gas—at about 10 million degrees Celsius—and holds it steady for 5 milliseconds without decaying away. That may seem a mere blink of an eye, but it is far longer than other efforts with the technique and shows for the first time that it is possible to hold the gas in a steady state—the researchers stopped only when their machine ran out of juice.

    “They’ve succeeded finally in achieving a lifetime limited only by the power available to the system,” says particle physicist Burton Richter of Stanford University in Palo Alto, California, who sits on a board of advisers to Tri Alpha. If the company’s scientists can scale the technique up to longer times and higher temperatures, they will reach a stage at which atomic nuclei in the gas collide forcefully enough to fuse together, releasing energy.

    “Until you learn to control and tame [the hot gas], it’s never going to work. In that regard, it’s a big deal. They seem to have found a way to tame it,” says Jaeyoung Park, head of the rival fusion startup Energy/Matter Conversion Corporation in San Diego. “The next question is how well can you confine [heat in the gas]. I give them the benefit of the doubt. I want to watch them for the next 2 or 3 years.”

    Although other startup companies are also trying to achieve fusion using similar methods, the main efforts in this field are huge government-funded projects such as the $20 billion International Thermonuclear Experimental Reactor (ITER), under construction in France by an international collaboration, and the U.S. Department of Energy’s $4 billion National Ignition Facility (NIF) in Livermore, California. But the burgeoning cost and complexity of such projects are causing many to doubt they will ever produce plants that can generate energy at an affordable cost.

    ITER Tokamak
    ITER tokamak

    LLNL NIF
    NIF

    [Thde author failed to mention The Princeton Plasma Physics Lab projects:
    Lithium Tokamak Experiment (LTX)
    PPPL LTX
    LTX
    National Spherical Torus Experiment (NSTX)
    PPPL NSTX
    NSTX
    PPPL’s original tokamak
    PPPL Tokamak
    PPPL Tokamak

    Tri Alpha’s and similar efforts take a different approach, which promises simpler, cheaper machines that can be developed more quickly. Importantly, the Tri Alpha machine may be able to operate with a different fuel than most other fusion reactors. This fuel—a mix of hydrogen and boron—is harder to react, but Tri Alpha researchers say it avoids many of the problems likely to confront conventional fusion power plants. “They are where they are because people are able to believe they can get a [hydrogen-boron] reactor to work,” says plasma physicist David Hammer of Cornell University, also a Tri Alpha adviser.

    But burning hydrogen-boron fuel requires truly enormous temperatures, more than 3 billion degrees Celsius, and that will be “very challenging,” says plasma physicist Jon Menard of the Princeton Plasma Physics Laboratory in New Jersey, who is not involved in the project. He says it’s very hard to predict how the gas will behave at higher temperatures. “I’m a little concerned that their [simulations] lag behind their experience,” he says, but the approach “is worth further investigation.”

    Like other fusion techniques, Tri Alpha’s device aims to confine a gas so hot that its atoms are stripped of electrons, producing a roiling mixture of electrons and ions known as plasma. If the ions collide with enough force, they fuse, converting some of their mass into energy, but this requires temperatures of at least 100 million degrees Celsius with conventional fuel, hot enough to melt any container. So the first challenge for reactor designers is how to confine the plasma without touching it. Facilities like the NIF rapidly implode the plasma, relying on its inward inertia to hold it long enough for a burst of fusion reactions. The ITER, in contrast, holds the plasma steady with powerful magnetic fields inside a doughnut-shaped chamber known as a tokamak. Some of the field is provided by a complex network of superconducting magnets, the rest by the plasma itself flowing around the ring like an electric current.

    Tri Alpha’s machine also produces a doughnut of plasma, but in it the flow of particles in the plasma produces all of the magnetic field holding the plasma together. This approach, known as a field-reversed configuration (FRC), has been known since the 1960s. But despite decades of work, researchers could get the blobs of plasma to last only about 0.3 milliseconds before they broke up or melted away. In 1997, the Canadian-born physicist Norman Rostoker of the University of California, Irvine, and colleagues proposed a new approach. The following year, they set up Tri Alpha, now based in an unremarkable—and unlabeled—industrial unit here. Building up from tabletop devices, by last year the company was employing 150 people and was working with C-2, a 23-meter-long tube ringed by magnets and bristling with control devices, diagnostic instruments, and particle beam generators. The machine forms two smoke rings of plasma, one near each end, by a proprietary process and fires them toward the middle at nearly a million kilometers per hour. At the center they merge into a bigger FRC, transforming their kinetic energy into heat.

    Previous attempts to create long-lasting FRCs were plagued by the twin demons that torment all fusion reactor designers. The first is turbulence in the plasma that allows hot particles to reach the edge and so lets heat escape. Second is instability: the fact that hot plasma doesn’t like being confined and so wriggles and bulges in attempts to get free, eventually breaking up altogether. Rostoker, a theorist who had worked in many branches of physics including particle physics, believed the solution lay in firing high-speed particles tangentially into the edge of the plasma. The fast-moving incomers would follow much wider orbits in the plasma’s magnetic field than native particles do; those wide orbits would act as a protective shell, stiffening the plasma against both heat-leaking turbulence and instability.

    To make it work, the Tri Alpha team needed to precisely control the magnetic conditions around the edge of the cigar-shaped FRC, which is as many as 3 meters long and 40 centimeters wide. They did it by penning the plasma in with magnetic fields generated by electrodes and magnets at each end of the long tube.

    In experiments carried out last year, C-2 showed that Rostoker was on the right track by producing FRCs that lasted 5 milliseconds, more than 10 times the duration previously achieved. “In 8 years they went from an empty room to an FRC lasting 5 milliseconds. That’s pretty good progress,” Hammer says. The FRCs, however, were still decaying during that time. The researchers needed to show they could replenish heat loss with the beams and create a stable FRC. So last autumn they dismantled C-2. In collaboration with Russia’s Budker Institute of Nuclear Physics in Akademgorodok, they upgraded the particle beam system, increasing its power from 2 megawatts to 10 megawatts and angling the beams to make better use of their power.

    The upgraded C-2U was back in operation by March. At a symposium today in memory of Rostoker, who died in December, Tri Alpha’s chief technology officer Michl Binderbauer announced that by June the new machine was producing FRCs lasting 5 milliseconds with no sign of decay; they remained the same size throughout.

    Binderbauer says that next year they will tear up C-2U again and build an almost entirely new machine, bigger and with even more powerful beams, dubbed C-2W. The aim is to achieve longer FRCs and, more crucially, higher temperature. A 10-fold increase in temperature would bring them into the realm of sparking reactions in conventional fusion fuel, a mixture of the hydrogen isotopes deuterium and tritium, known as D-T. But that is not their goal; instead, they’re working toward the much higher bar of hydrogen-boron fusion, which will require ion temperatures above 3 billion degrees Celsius.

    Researchers have several reasons for wanting to go that extra mile. First, tritium doesn’t occur naturally on Earth, so it has to be made by bombarding lithium with neutrons. Physicists plan to do this in the fusion reactors that will one day consume the tritium, but no one has shown that such a process is practical. Because D-T reactions also produce large quantities of high-energy neutrons, the reactors need thick shielding. But the neutrons still degrade the structure of the reactor and make it radioactive. Researchers don’t yet know if it will be possible to find radiation-hard materials capable of surviving the onslaught. Many think these make D-T fusion impractical for a commercial reactor. “I wouldn’t have spent 10 years on [Tri Alpha’s advisory] committee if it was working on a D-T system,” Richter says.

    Hydrogen-boron, at first, doesn’t look much more promising. “It takes 30 times as much energy to cook, and you get half as much energy out per particle,” Binderbauer says. But boron is abundant, and the reaction produces no neutrons, just three alpha particles (helium nuclei)—hence the company’s name. Hydrogen-boron fuel “makes conversion to electricity much easier and simpler,” Richter says.

    Says one investor in the company, who asked not to be named, “for the first time since we started investing, with this breakthrough it feels like the stone is starting to roll downhill rather than being pushed up it.”

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  • richardmitnick 9:34 pm on August 10, 2015 Permalink | Reply
    Tags: , Fusion technology, ,   

    From Princeton: “Scientists propose an explanation for electron heat loss in fusion plasmas (Physical Review Letters)” 

    Princeton University
    Princeton University

    August 10, 2015
    Raphael Rosen, Princeton Plasma Physics Laboratory

    Creating controlled fusion energy entails many challenges, but one of the most basic is heating plasma – hot gas composed of electrons and charged atoms – to extremely high temperatures and then maintaining those temperatures. Now scientist Elena Belova of the U.S. Department of Energy’s (DOE) Princeton Plasma Physics Laboratory (PPPL) and a team of collaborators have proposed an explanation for why the hot plasma within fusion facilities called tokamaks sometimes fails to reach the required temperature, even as researchers pump beams of fast-moving neutral atoms into the plasma in an effort to make it hotter.

    1
    PPPL Scientist Elena Belova. Photo Credit: Elle Starkman, PPPL

    The results, published in June in Physical Review Letters, could lead to improved control of temperature in future fusion devices, including ITER, the international fusion facility under construction in France to demonstrate the feasibility of fusion power. This work was supported by the DOE Office of Science (Office of Fusion Energy Sciences).

    ITER icon
    ITER Tokamak
    ITER tokamak

    The researchers focused on the puzzling tendency of electron heat to leak from the core of the plasma to the plasma’s edge. “One of the largest remaining mysteries in plasma physics is how electron heat is transported out of plasma,” said Jon Menard, program director for PPPL’s major fusion experiment, the National Spherical Tokamak Experiment-Upgrade (NSTX-U), which is completing a $94 million upgrade.

    PPPL NSTX-U
    NSTX-U

    Belova hit upon a possible answer while performing 3D simulations of past NSTX plasmas on computers at the National Energy Research Scientific Computing Center (NERSC), in Oakland, California. She saw that two kinds of waves found in fusion plasmas appear to form a chain that transfers the neutral-beam energy from the core of the plasma to the edge, where the heat dissipates. While physicists have long known that the coupling between the two kinds of waves – known as compressional Alfvén waves and kinetic Alfvén waves (KAWs) – can lead to energy dissipation in plasmas, Belova’s results were the first to demonstrate the process for beam-excited compressional Alfvén eigenmodes (CAEs) in tokamaks.

    Her simulations showed that when researchers try to heat the plasma by injecting beams of energetic deuterium, a form of hydrogen, the beams excite CAE waves in the plasma’s core. Those waves then resonate with KAW waves, which occur primarily at the plasma’s edge. As a result, the energy is transported from the injection site deep within the plasma to the plasma’s edge.

    “Originally, when scientists found that the electron temperature wouldn’t go up with increased beam power, everybody assumed that the electrons were getting heated at the plasma’s center and then were somehow losing that heat,” Belova said. “Our explanation is different. We propose that part of the beam energy goes into CAEs and then to KAWs. The energy then dissipates at the plasma’s edge.”

    The simulations provided a broad perspective. “In simulations you can look everywhere in a plasma,” Belova said. “In the experiments, on the other hand, you are very limited in what and where you can measure inside the hot plasma.”

    Belova’s findings reflect the growing collaboration between theoretical and experimental research at the Laboratory. “Her results uncover a novel loss mechanism for electron energy that could be important for NSTX-U plasmas,” said Amitava Bhattacharjee, head of the Theory Department at PPPL.

    Belova plans to run more simulations to determine whether the mechanism she identified is the primary process that modifies the electron heating profile. She will also look for ways in which physicists can avoid this wave-induced change in the profile. In the meantime, she is driven by her desire to learn more physics. “We want to understand how these waves are excited by the beam ions,” she said, “and how to avoid them in the experiments.”

    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, visit science.energy.gov.

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  • richardmitnick 9:02 am on August 10, 2015 Permalink | Reply
    Tags: , Fusion technology, ,   

    From phys.org: “New design could finally help to bring fusion power closer to reality” 

    physdotorg
    phys.org

    August 10, 2015
    David L. Chandler

    1
    A cutaway view of the proposed ARC reactor. Thanks to powerful new magnet technology, the much smaller, less-expensive ARC reactor would deliver the same power output as a much larger reactor. Credit: the MIT ARC team.

    It’s an old joke that many fusion scientists have grown tired of hearing: Practical nuclear fusion power plants are just 30 years away—and always will be.

    But now, finally, the joke may no longer be true: Advances in magnet technology have enabled researchers at MIT to propose a new design for a practical compact tokamak fusion reactor—and it’s one that might be realized in as little as a decade, they say. The era of practical fusion power, which could offer a nearly inexhaustible energy resource, may be coming near.

    Using these new commercially available superconductors, rare-earth barium copper oxide (REBCO) superconducting tapes, to produce high-magnetic field coils “just ripples through the whole design,” says Dennis Whyte, a professor of Nuclear Science and Engineering and director of MIT’s Plasma Science and Fusion Center. “It changes the whole thing.”

    The stronger magnetic field makes it possible to produce the required magnetic confinement of the superhot plasma—that is, the working material of a fusion reaction—but in a much smaller device than those previously envisioned. The reduction in size, in turn, makes the whole system less expensive and faster to build, and also allows for some ingenious new features in the power plant design. The proposed reactor, using a tokamak (donut-shaped) geometry that is widely studied, is described in a paper in the journal Fusion Engineering and Design, co-authored by Whyte, PhD candidate Brandon Sorbom, and 11 others at MIT. The paper started as a design class taught by Whyte and became a student-led project after the class ended.

    Power plant prototype

    The new reactor is designed for basic research on fusion and also as a potential prototype power plant that could produce significant power. The basic reactor concept and its associated elements are based on well-tested and proven principles developed over decades of research at MIT and around the world, the team says.

    “The much higher magnetic field,” Sorbom says, “allows you to achieve much higher performance.”

    Fusion, the nuclear reaction that powers the sun, involves fusing pairs of hydrogen atoms together to form helium, accompanied by enormous releases of energy. The hard part has been confining the superhot plasma—a form of electrically charged gas— while heating it to temperatures hotter than the cores of stars. This is where the magnetic fields are so important—they effectively trap the heat and particles in the hot center of the device.

    2
    MIT PhD candidate Brandon Sorbom holds REBCO superconducting tapes (left), which are the enabling technology behind the ARC reactor. When it is cooled to liquid nitrogen temperature, the superconducting tape can carry as much current as the large copper conductor on the right, enabling the construction of extremely high‑field magnets, which consume minimal amounts of power. Credit: Jose‑Luis Olivares/MIT

    While most characteristics of a system tend to vary in proportion to changes in dimensions, the effect of changes in the magnetic field on fusion reactions is much more extreme: The achievable fusion power increases according to the fourth power of the increase in the magnetic field. Thus, doubling the field would produce a 16-fold increase in the fusion power. “Any increase in the magnetic field gives you a huge win,” Sorbom says.

    Tenfold boost in power

    While the new superconductors do not produce quite a doubling of the field strength, they are strong enough to increase fusion power by about a factor of 10 compared to standard superconducting technology, Sorbom says. This dramatic improvement leads to a cascade of potential improvements in reactor design.

    The world’s most powerful planned fusion reactor, a huge device called ITER that is under construction in France, is expected to cost around $40 billion.

    ITER icon
    ITER Tokamak
    ITER tokamak

    Sorbom and the MIT team estimate that the new design, about half the diameter of ITER (which was designed before the new superconductors became available), would produce about the same power at a fraction of the cost and in a shorter construction time.

    But despite the difference in size and magnetic field strength, the proposed reactor, called ARC, is based on “exactly the same physics” as ITER, Whyte says. “We’re not extrapolating to some brand-new regime,” he adds.

    Another key advance in the new design is a method for removing the the fusion power core from the donut-shaped reactor without having to dismantle the entire device. That makes it especially well-suited for research aimed at further improving the system by using different materials or designs to fine-tune the performance.

    In addition, as with ITER, the new superconducting magnets would enable the reactor to operate in a sustained way, producing a steady power output, unlike today’s experimental reactors that can only operate for a few seconds at a time without overheating of copper coils.

    Liquid protection

    Another key advantage is that most of the solid blanket materials used to surround the fusion chamber in such reactors are replaced by a liquid material that can easily be circulated and replaced, eliminating the need for costly replacement procedures as the materials degrade over time.

    “It’s an extremely harsh environment for [solid] materials,” Whyte says, so replacing those materials with a liquid could be a major advantage.

    Right now, as designed, the reactor should be capable of producing about three times as much electricity as is needed to keep it running, but the design could probably be improved to increase that proportion to about five or six times, Sorbom says. So far, no fusion reactor has produced as much energy as it consumes, so this kind of net energy production would be a major breakthrough in fusion technology, the team says.

    The design could produce a reactor that would provide electricity to about 100,000 people, they say. Devices of a similar complexity and size have been built within about five years, they say.

    “Fusion energy is certain to be the most important source of electricity on earth in the 22nd century, but we need it much sooner than that to avoid catastrophic global warming,” says David Kingham, CEO of Tokamak Energy Ltd. in the UK, who was not connected with this research. “This paper shows a good way to make quicker progress,” he says.

    The MIT research, Kingham says, “shows that going to higher magnetic fields, an MIT speciality, can lead to much smaller (and hence cheaper and quicker-to-build) devices.” The work is of “exceptional quality,” he says; “the next step … would be to refine the design and work out more of the engineering details, but already the work should be catching the attention of policy makers, philanthropists and private investors.”

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    Phys.org™ (formerly Physorg.com) is a leading web-based science, research and technology news service which covers a full range of topics. These include physics, earth science, medicine, nanotechnology, electronics, space, biology, chemistry, computer sciences, engineering, mathematics and other sciences and technologies. Launched in 2004, Phys.org’s readership has grown steadily to include 1.75 million scientists, researchers, and engineers every month. Phys.org publishes approximately 100 quality articles every day, offering some of the most comprehensive coverage of sci-tech developments world-wide. Quancast 2009 includes Phys.org in its list of the Global Top 2,000 Websites. Phys.org community members enjoy access to many personalized features such as social networking, a personal home page set-up, RSS/XML feeds, article comments and ranking, the ability to save favorite articles, a daily newsletter, and other options.

     
  • richardmitnick 3:38 pm on July 23, 2015 Permalink | Reply
    Tags: , Fusion technology,   

    From New Scientist: “China spends big on nuclear fusion as French plan falls behind” 

    NewScientist

    New Scientist

    23 July 2015
    Fred Pearce

    1
    China’s will be bigger and better (Image: David Parker/SPL)

    The world’s largest nuclear fusion machine, currently being built in France, is unlikely to produce more energy than it consumes until the early 2030s, warned the UK’s head of fusion research this week. That is five years later than planned – by which time China could be ahead of everyone.

    Nuclear fusion involves heating a plasma of hydrogen isotopes so that they fuse into helium, releasing a large amount of energy in the process. Many physicists see it as the holy grail for producing cheap zero-carbon energy. But initiating the fusion reactions requires temperatures 10 times as hot as the core of the sun. And decades of experiments have yet to produce self-sustaining fusion reactions – known as “burning plasma” – that generate the energy required to produce such temperatures.

    The International Thermonuclear Experimental Reactor (ITER), a $20 billion machine being built in Cadarache, France, should get there.

    ITER Tokamak
    ITER icon
    ITER Tokamak

    “We are confident that it will,” Steven Cowley, director of the Culham Centre for Fusion Energy in Oxfordshire, told the science and technology committee of the UK’s House of Lords on Tuesday. But it is taking time and money.

    Burning plasma

    Constructing ITER has already cost three times as much as budgeted, and completion has slipped from 2016 to 2019, with the first plasma experiments the following year. Cowley told the committee: “ITER says 2020, but I believe the first plasma will be [generated] in 2025.” Burning plasma is unlikely before “the early 2030s”, he said. He likened the moment when burning plasma is achieved to the moment in the early 1940s when the first “critical” nuclear fission reactions were produced.

    Only then will the international researchers, many of whom have been working together for decades, move on to building a new plant that could generate continuous power – the forerunner for what they hope will be commercial nuclear fusion by late in the century. “But the biggest investment now is in China,” says Cowley. China is a collaborator on ITER, along with the European Union, the US and others. But it is investing heavily in building its own reactor, the China Fusion Engineering Test Reactor, which will be bigger than ITER and may be finished by 2030, he said.

    Cowley disclosed that some partners had discussed whether to continue collaboration with China or shut them out. “We decided to continue to collaborate.” Shutting China out “would only slow them down by a few months”, he told the Lords, who are investigating whether the UK government is getting value for money in its fusion investments. Fusion currently accounts for 14 per cent of UK government spending on energy research, Sharon Ellis of the Department for Business, Innovation and Skills told the committee.

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  • richardmitnick 2:21 pm on July 21, 2015 Permalink | Reply
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    From LANL: “Los Alamos among new DOE projects to create new technology pathways for low-cost fusion energy development” 

    LANL bloc

    LANL Sign
    Los Alamos National Laboratory

    July 20, 2015
    Communications Office
    (505) 667-7000

    Three of the projects involve Los Alamos National Laboratory science staff and partners.

    The Energy Department’s Advanced Research Projects Agency-Energy (ARPA-E) on May 14, 2015 announced $30 million in funding for 9 groundbreaking new projects aimed at developing prototype technologies to explore new pathways for fusion power. Three of the projects involve Los Alamos National Laboratory science staff and partners.

    The projects are funded through ARPA-E’s Accelerating Low-cost Plasma Heating and Assembly (ALPHA) program, which seeks to develop low-cost fusion energy technology solutions.

    “These new projects emphasize ARPA-E’s commitment to developing a wide range of technology options to ensure a more affordable and sustainable energy future,” said ARPA-E Director Dr. Ellen D. Williams. “Investing in … intermediate density fusion illustrates ARPA-E’s role in accelerating energy research and development.”

    Details on ALPHA’s nine projects may be found here.

    The Los Alamos National Laboratory projects are the following:

    Spherically Imploding Plasma Liners as a Standoff Magneto-Inertial-Fusion Driver- $5,875,000

    Los Alamos National Laboratory (LANL), teamed with Hyper V Technologies and a multi-institutional team, will develop a plasma-liner driver formed by merging supersonic plasma jets produced by an array of coaxial plasma guns.

    2

    The key virtues of a plasma-liner driver, as noted by project leader Scott Hsu, are that it (1) has standoff, i.e., it completely avoids hardware destruction because the plasma guns are placed sufficiently far away (many meters in an eventual fusion reactor) from the region of fusion burn, and (2) it enables high implosion velocity (50–100 km/s) to overcome thermal transport rates inherent in desired targets.

    This non-destructive approach may enable rapid, low cost research and development and, by avoiding replacement of solid components on every shot, may help lead to an economically attractive power reactor. This project will seek to demonstrate, for the first time, the formation of a small scale spherically imploding plasma liner in order to obtain critical data on plasma liner uniformity and ram pressure scaling. If successful, this concept will provide a versatile, high-implosion-velocity driver for intermediate fuel density magneto-inertial fusion that is potentially compatible with several plasma targets. These experiments will be conducted on the existing Plasma Liner Experiment (PLX) facility at Technical Area 35 at Los Alamos.

    Stabilized Liner Compressor (SLC) for Low-Cost Fusion

    NumerEx, LLC, teamed with the National High Magnetic Field Laboratory in Los Alamos, NM, will develop the Stabilized Liner Compressor (SLC) concept in which a rotating, liquid metal liner is imploded by high-pressure gas.

    3

    The Stabilized Liner Compressor (SLC) is a system that uses high-pressure gas and a free-piston to implode a liquid metal liner onto trapped magnetic flux in order to achieve controlled fusion at very high magnetic fields (~100 T).

    “The SLC project provides an opportunity to leverage advances in materials in a new era of computation capabilities while developing a revolutionary high magnetic field capability with a distinct purpose,” said Los Alamos project leader Chuck Mielke.

    Free-piston drive and liner rotation avoid instabilities as the liner compresses and heats a plasma target. If successful, this concept could scale to an attractive fusion reactor with efficient energy recovery, and therefore a low required minimum fusion gain for net energy output. The SLC will address several challenges faced by practical fusion reactors. By surrounding the plasma target with a thick liquid liner, the SLC helps avoid materials degradation associated with a solid plasma-facing first wall. In addition, with an appropriately chosen liner material, the SLC can simultaneously provide a breeding blanket to create more tritium fuel, allow efficient heat transport out of the reactor, and shield solid components of the reactor from high-energy neutrons.

    “We recognized back at the Naval Research Laboratory in the 1970s that there may exist an optimum regime for controlled fusion at much higher magnetic fields than used by the mainline magnetic fusion program, but at much lower power density than required for laser fusion. The resulting power reactor and the necessary experimental prototypes need the repetitive, stabilized operation at megagauss field-levels offered by SLC,” said Peter J. Turchi, Los Alamos Guest Scientist and Senior Consultant to NumerEx LLC.

    Prototype Tools to Establish the Viability of the Adiabatic Heating and Compression Mechanisms Required for Magnetized Target Fusion

    Caltech, in coordination with Los Alamos National Laboratory, will investigate collisions of plasma jets and targets over a wide range of parameters to characterize the scaling of adiabatic heating and compression of liner-driven magnetized target fusion plasmas.

    4

    “Los Alamos will provide plasma physics modeling of the experiments to be carried out at Caltech to understand the critical processes during the plasma-cloud interactions,” said Hui Li, the lead Los Alamos scientist on the project.

    The team will propel fast, magnetized plasma jets into stationary heavy gases or metal walls. The resulting collision is equivalent to a fast heavy gas or metal liner impacting a stationary magnetized target in a shifted reference frame and allows the non-destructive and rapid investigation of physical phenomena and scaling laws governing the degree of adiabaticity of liner implosions. This study will provide critical information on the interactions and limitations for a variety of possible driver and plasma target combinations being developed across the ALPHA program portfolio.

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  • richardmitnick 9:26 am on June 3, 2015 Permalink | Reply
    Tags: , Fusion technology,   

    From U Washington: “UW researchers scaling up fusion hopes with DOE grant” 

    U Washington

    University of Washington

    June 2, 2015
    Jennifer Langston

    1
    UW researchers will attempt to create a self-sustained and controlled fusion reaction with a scaled-up version of this Z-pinch device. University of Washington

    Producing reliable fusion energy — the same process that powers the sun — has long been a holy grail of scientists here on Earth. It releases no greenhouse gases, can be fueled by elements found in seawater and produces no long-lived nuclear waste.

    The basic mechanism — getting two nuclei that want nothing to do with each other to fuse — is also difficult enough that there’s no danger of a runaway chain reaction. In fact, scientists so far have struggled to create self-sustained controlled fusion reactions that produce more energy than they consume.

    University of Washington researchers have spent two decades developing a novel way to provide plasma stability that’s critical to achieving fusion. With a $5.3 million U.S. Department of Energy grant announced in May, they will partner with Lawrence Livermore National Laboratory to scale up their “Sheared Flow Stabilized Z-Pinch” device in the hopes of achieving a sustainable fusion reaction that might one day power homes or propel spaceships far beyond current limitations.

    “Fusion energy is the ultimate energy source. It’s free of greenhouses gases, and it also has the potential to be a very robust source without the reliability problems of wind and solar,” said UW professor of aeronautics and astronautics Uri Shumlak, who collaborated with UW electrical engineering professor Brian Nelson to develop the device.

    It will be the first time that UW researchers have built a fusion device on campus, Shumlak said.

    “Researchers generally don’t achieve adequate plasma conditions to produce significant fusion reactions,” said Shumlak. “Our project will be a proof-of-principle experiment, and just showing that the sheared flow stabilized Z-pinch approach scales to higher powers is going to be really exciting.”

    Fusion is the opposite of fission, which splits heavier atoms apart and produces the energy that powers commercial nuclear reactors. Fusing smaller atoms together can yield even greater amounts of energy but does not typically produce unpredictable radioactive isotopes or long-lived radioactive waste. The UW’s experiments, for instance, would be fueled by stable and harmless isotopes of hydrogen that are widely available in nature.

    The fusion process does produce neutrons that can pose hazards if not properly controlled, but their behavior is well understood. Neutron therapy, for instance, is used to treat certain types of cancers. UW researchers will closely monitor emissions and follow well-established protocols to ensure those levels pose no risks.

    2
    The Sheared Flow Stabilized Z-Pinch has a simple, linear configuration and uses sheared axial flows to prevent plasma instabilities from growing. The concept is similar to cars in the center lane of the highway being prevented from changing lanes by faster moving traffic on either side. University of Washington

    Most university research has focused on the basic science involved in creating, confining and stabilizing plasma, which is a basic ingredient for fusion. Often called the “fourth state of matter,” plasma forms when a gas is so superheated that electrons are ripped apart from an atom’s nucleus.

    Applying enough energy to this swirl of negatively and positively charged particles can induce the nuclei to fuse. Under the right conditions — which have proved devilishly difficult to create outside of stars like the sun — this process gives off more energy than it consumes.

    One problem is that simply creating plasma requires such high temperatures — typically greater than 200,000 degrees Fahrenheit — that nothing material can contain it without disintegrating or melting. One approach to fusion research uses magnetic fields, often generated by gigantic coils that are many stories high, to contain the plasma.

    3
    UW Aeronautics and Astronautics professor Uri Shumlak and student Bonghan Kim work on an earlier prototype of the Z-pinch device.University of Washington

    The UW researchers have used a Z-pinch, which is a geometrically simple and elegant approach to fusion that uses an electric current to magnetically confine, compress and heat a long cylinder of flowing plasma. It requires no magnetic coils, which means that the device could be much smaller, cheaper and more versatile than some of the massive fusion machines under development today.

    One historic problem with the z-pinch is that the interface between the plasma and the magnetic fields is unstable. They essentially try to invert and trade places, just like a layer of water laid on top of a layer of oil will try to flip. The UW researchers have developed an accelerator that manipulates the properties of the plasma itself to create more stable conditions — at least at lower temperatures.

    “Sheared flow stabilization uses plasma moving at different speeds in different places to prevent plasma instabilities from growing,” said Shumlak. “It’s something like cars in the center lane of a freeway that are prevented from changing lanes by higher speed traffic on both sides.”

    The 3-year DOE grant will enable the researchers to test if the concept still works at temperatures high enough to create fusion conditions, about 20 million degrees F. They will need to increase the amount of energy that has been injected into the Z-pinches they’ve built to date by more than tenfold.

    The UW researchers are collaborating with scientists Harry McLean and Andréa Schmidt of Lawrence Livermore National Laboratory, who provide expertise in designing the higher-energy power supplies and detecting neutrons as evidence that atoms have fused.

    The team plans to build a new Z-pinch device at the UW by summer of 2016 and run its first fusion tests in 2017.

    “Essentially, we need to determine if we can scale the sheared flow stabilized Z-pinch,” said Nelson. “As we go to higher Z-pinch currents by injecting more energy, does it still stabilize and compress the plasma? Or, put more simply, does the concept still work?”

    Funding for the project comes from the U.S. Department of Energy’s Advanced Research Projects Agency-Energy (ARPA-E).

    For more information, contact Shumlak at shumlak@uw.edu.

    See the full article here.

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    The University of Washington is one of the world’s preeminent public universities. Our impact on individuals, on our region, and on the world is profound — whether we are launching young people into a boundless future or confronting the grand challenges of our time through undaunted research and scholarship. Ranked number 10 in the world in Shanghai Jiao Tong University rankings and educating more than 54,000 students annually, our students and faculty work together to turn ideas into impact and in the process transform lives and our world. For more about our impact on the world, every day.

    So what defines us — the students, faculty and community members at the University of Washington? Above all, it’s our belief in possibility and our unshakable optimism. It’s a connection to others, both near and far. It’s a hunger that pushes us to tackle challenges and pursue progress. It’s the conviction that together we can create a world of good. Join us on the journey.

     
  • richardmitnick 2:48 pm on June 2, 2015 Permalink | Reply
    Tags: , Fusion technology, ,   

    From PPPL: “Giant structures called plasmoids could simplify the design of future tokamaks” 


    PPPL

    June 2, 2015
    Raphael Rosen

    1
    Left: Plasmoid formation in simulation of NSTX plasma during CHI / Right: Fast-camera image of NSTX plasma shows two discrete plasmoid-like bubble structures. (Photo by Left: Fatima Ebrahimi, PPPL / Right: Nishino-san, Hiroshima University)

    Researchers at the U.S. Department of Energy’s Princeton Plasma Physics Laboratory (PPPL) have for the first time simulated the formation of structures called “plasmoids” during Coaxial Helicity Injection (CHI), a process that could simplify the design of fusion facilities known as tokamaks. The findings, reported in the journal Physical Review Letters, involve the formation of plasmoids in the hot, charged plasma gas that fuels fusion reactions. These round structures carry current that could eliminate the need for solenoids – large magnetic coils that wind down the center of today’s tokamaks – to initiate the plasma and complete the magnetic field that confines the hot gas.

    PPPL Tokamak
    PPPL Tokamak

    “Understanding this behavior will help us produce plasmas that undergo fusion reactions indefinitely,” said Fatima Ebrahimi, a physicist at both Princeton University and PPPL, and the paper’s lead author.

    Ebrahimi ran a computer simulation that modeled the behavior of plasma and the formation of plasmoids in three dimensions thoughout a tokamak’s vacuum vessel. This marked the first time researchers had modeled plasmoids in conditions that closely mimicked those within an actual tokamak. All previous simulations had modeled only a thin slice of the plasma – a simplified picture that could fail to capture the full range of plasma behavior.

    Researchers validated their model by comparing it with fast-camera images of plasma behavior inside the National Spherical Torus Experiment (NSTX), PPPL’s major fusion facility.

    PPPL NSTX
    PPPL NSTX

    These images also showed plasmoid-like structures, confirming the simulation and giving the research breakthrough significance, since it revealed the existence of plasmoids in an environment in which they had never been seen before. “These findings are in a whole different league from previous ones,” said Roger Raman, leader for the Coaxial Helicity Injection Research program on NSTX and a coauthor of the paper.

    The findings may provide theoretical support for the design of a new kind of tokamak with no need for a large solenoid to complete the magnetic field. Solenoids create magnetic fields when electric current courses through them in relatively short pulses. Today’s conventional tokamaks, which are shaped like a donut, and spherical tokamaks, which are shaped like a cored apple, both employ solenoids. But future tokamaks will need to operate in a constant or steady state for weeks or months at a time. Moreover, the space in which the solenoid fits – the hole in the middle of the doughnut-shaped tokamak – is relatively small and limits the size and strength of the solenoid.

    A clear understanding of plasmoid formation could thus lead to a more efficient method of creating and maintaining a plasma through transient Coaxial Helicity Injection. This method, originally developed at the University of Washington, could dispense with a solenoid entirely and would work like this:

    Researchers first inject open magnetic field lines into the vessel from the bottom of the vacuum chamber. As researchers drive electric current along those magnetic lines, the lines snap closed and form the plasmoids, much like soap bubbles being blown out of a sheet of soapy film.
    The many plasmoids would then merge to form one giant plasmoid that could fill the vacuum chamber.
    The magnetic field within this giant plasmoid would induce a current in the plasma to keep the gas tightly in place. “In principle, CHI could fundamentally change how tokamaks are built in the future,” says Raman.

    Understanding how the magnetic lines in plasmoids snap closed could also help solar physicists decode the workings of the sun. Huge magnetic lines regularly loop off the surface of the star, bringing the sun’s hot plasma with them. These lines sometimes snap together to form a plasmoid-like mass that can interfere with communications satellites when it collides with the magnetic field that surrounds the Earth.

    While Ebrahimi’s findings are promising, she stresses that much more is to come. PPPL’s National Spherical Torus Experiment-Upgrade (NSTX-U) will provide a more powerful platform for studying plasmoids when it begins operating this year, making Ebrahimi’s research “only the beginning of even more exciting work that will be done on PPPL equipment,” she said.

    See the full article here.

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    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 9:02 pm on May 22, 2015 Permalink | Reply
    Tags: , Fusion technology,   

    From PPPL: “A little drop will do it: Tiny grains of lithium can dramatically improve the performance of fusion plasmas” 


    PPPL

    May 22, 2015
    Raphael Rosen

    1
    Left: DIII-D tokamak. Right: Cross-section of plasma in which lithium has turned the emitted light green. (Credits: Left, General Atomics / Right, Steve Allen, Lawrence Berkeley National Laboratory)

    Scientists from General Atomics and the U.S. Department of Energy’s (DOE) Princeton Plasma Physics Laboratory (PPPL) have discovered a phenomenon that helps them to improve fusion plasmas, a finding that may quicken the development of fusion energy. Together with a team of researchers from across the United States, the scientists found that when they injected tiny grains of lithium into a plasma undergoing a particular kind of turbulence then, under the right conditions, the temperature and pressure rose dramatically. High heat and pressure are crucial to fusion, a process in which atomic nuclei – or ions – smash together and release energy — making even a brief rise in pressure of great importance for the development of fusion energy.

    “These findings might be a step towards creating our ultimate goal of steady-state fusion, which would last not just for milliseconds, but indefinitely,” said Tom Osborne, a physicist at General Atomics and lead author of the paper. This work was supported by the DOE Office of Science.

    The scientists used a device developed at PPPL to inject grains of lithium measuring some 45 millionths of a meter in diameter into a plasma in the DIII-D National Fusion Facility – or tokamak – that General Atomics operates for DOE in San Diego.

    DOE DIII-D Tokamak
    DIII-D National Fusion Facility

    When the lithium was injected while the plasma was relatively calm, the plasma remained basically unaltered. Yet as reported this month in a paper in Nuclear Fusion, when the plasma was undergoing a kind of turbulence known as a “bursty chirping mode,” the injection of lithium doubled the pressure at the outer edge of the plasma. In addition, the length of time that the plasma remained at high pressure rose by more than a factor of 10.

    Experiments have sustained this enhanced state for up to one-third of a second. A key scientific objective will be to extend this enhanced performance for the full duration of a plasma discharge.

    Physicists have long known that adding lithium to a fusion plasma increases its performance. The new findings surprised researchers, however, since the small amount of lithium raised the plasma’s temperature and pressure more than had been expected.

    These results “could represent the birth of a new tool for influencing or perhaps controlling tokamak edge physics,” said Dennis Mansfield, a physicist at PPPL and a coauthor of the paper who helped develop the injection device called a “lithium dropper.” Also working on the experiments were researchers from Lawrence Livermore National Laboratory, Oak Ridge National Laboratory, the University of Wisconsin-Madison and the University of California-San Diego.

    Conditions at the edge of the plasma have a profound effect on the superhot core of the plasma where fusion reactions take place. Increasing pressure at the edge region raises the pressure of the plasma as a whole. And the greater the plasma pressure, the more suitable conditions are for fusion reactions. “Making small changes at the plasma’s edge lets us increase the pressure further within the plasma,” said Rajesh Maingi, manager of edge physics and plasma-facing components at PPPL and a coauthor of the paper.

    Further experiments will test whether the lithium’s interaction with the bursty chirping modes — so-called because the turbulence occurs in pulses and involves sudden changes in pitch — caused the unexpectedly strong overall effect.

    See the full article here.

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    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 7:53 am on May 22, 2015 Permalink | Reply
    Tags: , , Fusion technology   

    From AAAS: “The new shape of fusion” 

    AAAS

    AAAS

    21 May 2015
    Daniel Clery

    1
    A plasma glows inside MAST, a spherical tokamak.

    ITER, the international fusion reactor being built in France, will stand 10 stories tall, weigh three times as much as the Eiffel Tower, and cost its seven international partners $18 billion or more. The result of decades of planning, ITER will not produce fusion energy until 2027 at the earliest. And it will be decades before an ITER-like plant pumps electricity into the grid. Surely there is a quicker and cheaper route to fusion energy.

    Fusion enthusiasts have a slew of schemes for achieving the starlike temperatures or crushing pressures needed to get hydrogen nuclei to come together in an energy-spawning union. Some are mainstream, such as lasers, some unorthodox. Yet the doughnut-shaped vessels called tokamaks, designed to cage a superheated plasma using magnetic fields, remain the leading fusion strategy and are the basis of ITER. Even among tokamaks, however, a nimbler alternative has emerged: a spherical tokamak.

    Imagine the doughnut shape of a conventional tokamak plumped up into a shape more like a cored apple. That simple change, say the idea’s advocates, could open the way to a fusion power plant that would match ITER’s promise, without the massive scale. “The aim is to make tokamaks smaller, cheaper, and faster—to reduce the eventual cost of electricity,” says Ian Chapman, head of tokamak science at the Culham Centre for Fusion Energy in Abingdon, U.K.


    Download mp4 here.

    Culham is one of two labs about to give these portly tokamaks a major test. The world’s two front-rank machines—the National Spherical Torus Experiment (NSTX) at the Princeton Plasma Physics Laboratory in New Jersey and the Mega Amp Spherical Tokamak (MAST) in Culham—are both being upgraded with stronger magnets and more powerful heating systems. Soon they will switch on and heat hydrogen to temperatures much closer to those needed for generating fusion energy. If they perform well, then the next major tokamak to be built—a machine that would run in parallel with ITER and test technology for commercial reactors—will likely be a spherical tokamak.

    PPPL NSTX
    NSTX

    Mega Amp Spherical Tokamak
    MAST

    A small company spun off from Culham is even making a long-shot bet that it can have a spherical tokamak reactor capable of generating more energy than it consumes—one of ITER’s goals—up and running within the decade. If it succeeds, spherical tokamaks could change the shape of fusion’s future. “It’s going to be exciting,” says Howard Wilson, director of the York Plasma Institute at the University of York in the United Kingdom. “Spherical tokamaks are the new kids on the block. But there are still important questions we’re trying to get to the bottom of.”

    TOKAMAKS ARE AN INGENIOUS WAY to cage one of the most unruly substances humans have ever grappled with: plasma hot enough to sustain fusion. To get nuclei to slam together and fuse, fusion reactors must reach temperatures 10 times hotter than the core of the sun, about 150 million degrees Celsius. The result is a tenuous ionized gas that would vaporize any material it touches—and yet must be held in place long enough for fusion to generate useful amounts of energy.

    Tokamaks attempt this seemingly impossible task using magnets, which can hold and manipulate plasma because it is made of charged particles. A complex set of electromagnets encircle the doughnut-shaped vessel, some horizontal and some vertical, while one tightly wound coil of wire, called a solenoid, runs down the doughnut hole. Their combined magnetic field squeezes the plasma toward the center of the tube and drives it around the ring while also twisting in a slow corkscrew motion.

    But plasma is not easy to master. Confining it is like trying to squeeze a balloon with your hands: It likes to bulge out between your fingers. The hotter a plasma gets, the more the magnetically confined gas bulges and wriggles and tries to escape. Much of the past 60 years of fusion research has focused on how to control plasma.

    Generating and maintaining enough heat for fusion has been another challenge. Friction generated as the plasma surges around the tokamak supplies some of the heat, but modern tokamaks also beam in microwaves and high-energy particles. As fast as the heat is supplied, it bleeds away, as the hottest, fastest moving particles in the turbulent plasma swirl away from the hot core toward the cooler edge. “Any confinement system is going to be slightly leaky and will lose particles,” Wilson says.

    Studies of tokamaks of different sizes and configurations have always pointed to the same message: To contain a plasma and keep it hot, bigger is better. In a bigger volume, hot particles have to travel farther to escape. Today’s biggest tokamak, the 8-meter-wide Joint European Torus (JET) at Culham, set a record for fusion energy in 1997, generating 16 megawatts for a few seconds.

    Joint European Torus
    JET

    (That was still slightly less than the heating power pumped into the plasma.) For most of the fusion community, ITER is the logical next step. It is expected to be the first machine to achieve energy gain—more fusion energy out than heating power in.

    In the 1980s, a team at Oak Ridge National Laboratory in Tennessee explored how a simple shape change could affect tokamak performance. They focused on the aspect ratio—the radius of the whole tokamak compared to the radius of the vacuum tube. (A Hula-Hoop has a very high aspect ratio, a bagel a lower one.) Their calculations suggested that making the aspect ratio very low, so that the tokamak was essentially a sphere with narrow hole through the middle, could have many advantages.

    Near a spherical tokamak’s central hole, the Oak Ridge researchers predicted, particles would enjoy unusual stability. Instead of corkscrewing lazily around the tube as in a conventional tokamak, the magnetic field lines wind tightly around the central column, holding particles there for extended periods before they return to the outside surface. The D-shaped cross section of the plasma would also help suppress turbulence, improving energy confinement. And they reckoned that the new shape would use magnetic fields more efficiently—achieving more plasma pressure for a given magnetic pressure, a ratio known as beta. Higher beta means more bang for your magnetic buck. “The general idea of spherical tokamaks was to produce electricity on a smaller scale, and more cheaply,” Culham’s Chapman says.

    But such a design posed a practical problem. The narrow central hole in a spherical tokamak didn’t leave enough room for the equipment that needs to fit there: part of each vertical magnet plus the central solenoid. In 1984, Martin Peng of Oak Ridge came up with an elegant, space-saving solution: replace the multitude of vertical ring magnets with C-shaped rings that share a single conductor down the center of the reactor (see graphic, below).

    3
    JAMES PROVOST

    U.S. fusion funding was in short supply at that time, so Oak Ridge could not build a spherical machine to test Peng’s design. A few labs overseas converted some small devices designed for other purposes into spherical tokamaks, but the first true example was built at the Culham lab in 1990. “It was put together on a shoestring with parts from other machines,” Chapman says. Known as the Small Tight Aspect Ratio Tokamak (START), the device soon achieved a beta of 40%, more than three times that of any conventional tokamak.

    It also bested traditional machines in terms of stability. “It smashed the world record at the time,” Chapman says. “People got more interested.” Other labs rushed to build small spherical tokamaks, some in countries not known for their fusion research, including Australia, Brazil, Egypt, Kazakhstan, Pakistan, and Turkey.

    The next question, Chapman says, was “can we build a bigger machine and get similar performance?” Princeton and Culham’s machines were meant to answer that question. Completed in 1999, NSTX and MAST both hold plasmas about 3 meters across, roughly three times bigger than START’s but a third the size of JET’s. The performance of the pair showed that START wasn’t a one-off: again they achieved a beta of about 40%, reduced instabilities, and good confinement.

    Now, both machines are moving to the next stage: more heating power to make a hotter plasma and stronger magnets to hold it in place. MAST is now in pieces, the empty vacuum vessel looking like a giant tin can adorned with portholes, while its €30 million worth of new magnets, pumps, power supplies, and heating systems are prepared. At Princeton, technicians are putting the finishing touches to a similar $94 million upgrade of NSTX’s magnets and neutral beam heating. Like most experimental tokamaks, the two machines are not aiming to produce lots of energy, just learning how to control and confine plasma under fusionlike conditions. “It’s a big step,” Chapman says. “NSTX-U will have really high injected power in a small plasma volume. Can you control that plasma? This is a necessary step before you could make a spherical tokamak power plant.”

    4
    Engineers lift out MAST’s vacuum vessel for modifications during the €30 million upgrade. © CCFE

    The upgraded machines will each have a different emphasis. NSTX-U, with the greater heating power, will focus on controlling instabilities and improving confinement when it restarts this summer.

    PPPL NSTX-U
    NSTX-U

    “If we can get reasonable beta values, [NSTXU] will reach plasma [properties] similar to conventional tokamaks,” says NSTX chief Masayuki Ono. MAST-Upgrade, due to fire up in 2017, will address a different problem: capturing the fusion energy that would build up in a full-scale plant.

    Fusion reactions generate most of their energy in the form of high-energy neutrons, which, being neutral, are immune to magnetic fields and can shoot straight out of the reactor. In a future power plant, a neutron-absorbing material will capture them, converting their energy to heat that will drive a steam turbine and generate electricity. But 20% of the reaction energy heats the plasma directly and must somehow be tapped. Modern tokamaks remove heat by shaping the magnetic field into a kind of exhaust pipe, called a divertor, which siphons off some of the outermost layer of plasma and pipes it away. But fusion heat will build up even faster in a spherical tokamak because of its compact size. MAST-Upgrade has a flexible magnet system so that researchers can try out various divertor designs, looking for one that can cope with the heat.

    Researchers know from experience that when a tokamak steps up in size or power, plasma can start misbehaving in new ways. “We need MAST and NSTX to make sure there are no surprises at low aspect ratio,” says Dennis Whyte, director of the Plasma Science and Fusion Center at the Massachusetts Institute of Technology in Cambridge. Once NSTX and MAST have shown what they are capable of, Wilson says, “we can pin down what a [power-producing] spherical tokamak will look like. If confinement is good, we can make a very compact machine, around MAST size.”

    BUT GENERATING ELECTRICITY isn’t the only potential goal. The fusion community will soon have to build a reactor to test how components for a future power plant would hold up under years of bombardment by high-energy neutrons. That’s the goal of a proposed machine known in Europe as the Component Test Facility (CTF), which could run stably around the clock, generating as much heat from fusion as it consumes. A CTF is “absolutely necessary,” Chapman says. “It’s very important to test materials to make reactors out of.” The design of CTF hasn’t been settled, but spherical tokamak proponents argue their design offers an efficient route to such a testbed—one that “would be relatively compact and cheap to build and run,” Ono says.

    With ITER construction consuming much of the world’s fusion budget, that promise won’t be tested anytime soon. But one company hopes to go from a standing start to a small power-producing spherical tokamak in a decade. In 2009, a couple of researchers from Culham created a spinoff company—Tokamak Solutions—to build small spherical tokamaks as neutron sources for research. Later, one of the company’s suppliers showed them a new multilayered conducting tape, made with the high-temperature superconductor yttrium-barium-copper-oxide, that promised a major performance boost.

    Lacking electrical resistance, superconductors can be wound into electromagnets that produce much stronger fields than conventional copper magnets. ITER will use low-temperature superconductors for its magnets, but they require massive and expensive cooling. High-temperature materials are cheaper to use but were thought to be unable to withstand the strong magnetic fields around a tokamak—until the new superconducting tape came along. The company changed direction, was renamed Tokamak Energy, and is now testing a first-generation superconducting spherical tokamak no taller than a person.

    Superconductors allow a tokamak to confine a plasma for longer. Whereas NSTX and MAST can run for only a few seconds, the team at Tokamak Energy this year ran their machine—albeit at low temperature and pressure—for more than 15 minutes. In the coming months, they will attempt a 24-hour pulse—smashing the tokamak record of slightly over 5 hours.

    Next year, the company will put together a slightly larger machine able to produce twice the magnetic field of NSTX-U. The next step—investors permitting—will be a machine slightly smaller than Princeton’s but with three times the magnetic field. Company CEO David Kingham thinks that will be enough to beat ITER to the prize: a net gain of energy. “We want to get fusion gain in 5 years. That’s the challenge,” he says.

    “It’s a high-risk approach,” Wilson says. “They’re buying their lottery ticket. If they win, it’ll be great. If they don’t, they’ll likely disappear. Even if it doesn’t work, we’ll learn from it; it will accelerate the fusion program.”

    It’s a spirit familiar to everyone trying to reshape the future of fusion.

    See the full article here.

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  • richardmitnick 1:18 pm on April 28, 2015 Permalink | Reply
    Tags: , Fusion technology, ,   

    From PPPL at Princeton: “An improvement to the global software standard for analyzing fusion plasmas (Nuclear Fusion)” 

    Princeton University
    Princeton University

    PPPL Large
    PPPL

    April 28, 2015
    Raphael Rosen, Princeton Plasma Physics Laboratory

    The gold standard for analyzing the behavior of fusion plasmas may have just gotten better. Mario Podestà, a staff physicist at the U.S. Department of Energy’s Princeton Plasma Physics Laboratory (PPPL), has updated the worldwide computer program known as TRANSP to better simulate the interaction between energetic particles and instabilities – disturbances in plasma that can halt fusion reactions. The program’s updates, reported in the journal Nuclear Fusion, could lead to improved capability for predicting the effects of some types of instabilities in future facilities such as ITER, the international experiment under construction in France to demonstrate the feasibility of fusion power.

    ITER Tokamak
    ITER Tokamak

    Podestà and co-authors saw a need for better modeling techniques when they noticed that while TRANSP could accurately simulate an entire plasma discharge, the code wasn’t able to represent properly the interaction between energetic particles and instabilities. The reason was that TRANSP, which PPPL developed and has regularly updated, treated all fast-moving particles within the plasma the same way. Those instabilities, however, can affect different parts of the plasma in different ways through so-called “resonant processes.”

    The authors first figured out how to condense information from other codes that do model the interaction accurately – albeit over short time periods – so that TRANSP could incorporate that information into its simulations. Podestà then teamed up with TRANSP developer Marina Gorelenkova at PPPL to update a TRANSP module called NUBEAM to enable it to make sense of this condensed data. “Once validated, the updated module will provide a better and more accurate way to compute the transport of energetic particles,” said Podestà. “Having a more accurate description of the particle interactions with instabilities can improve the fidelity of the program’s simulations.”

    1
    Schematic of NSTX tokamak at PPPL with a cross-section showing perturbations of the plasma profiles caused by instabilities. Without instabilities, energetic particles would follow closed trajectories and stay confined inside the plasma (blue orbit). With instabilities, trajectories can be modified and some particles may eventually be pushed out of the plasma boundary and lost (red orbit). Credit: Mario Podestà

    Fast-moving particles, which result from neutral beam injection into tokamak plasmas, cause the instabilities that the updated code models. These particles begin their lives with a neutral charge but turn into negatively charged electrons and positively charged ions – or atomic nuclei – inside the plasma. This scheme is used to heat the plasma and to drive part of the electric current that completes the magnetic field confining the plasma.

    PPPL Tokamak
    PPPL Tokamak

    The improved simulation tool may have applications for ITER, which will use fusion end-products called alpha particles to sustain high plasma temperatures. But just like the neutral beam particles in current-day-tokamaks, alpha particles could cause instabilities that degrade the yield of fusion reactions. “In present research devices, only very few, if any, alpha particles are generated,” said Podestà. “So we have to study and understand the effects of energetic ions from neutral beam injectors as a proxy for what will happen in future fusion reactors.”

    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, visit science.energy.gov.

    See the full article here.

    Please help promote STEM in your local schools.

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    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.

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