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  • richardmitnick 2:48 pm on June 2, 2015 Permalink | Reply
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    From PPPL: “Giant structures called plasmoids could simplify the design of future tokamaks” 


    June 2, 2015
    Raphael Rosen

    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.


    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 7:24 am on February 17, 2015 Permalink | Reply
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    From physicsworld: “Smaller fusion reactors could deliver big gains” 


    Feb 16, 2015
    Michael Banks

    Hot topic: size may not be everything in tokamak design

    Researchers from the UK firm Tokamak Energy say that future fusion reactors could be made much smaller than previously envisaged – yet still deliver the same energy output. That claim is based on calculations showing that the fusion power gain – a measure of the ratio of the power from a fusion reactor to the power required to maintain the plasma in steady state – does not depend strongly on the size of the reactor. The company’s finding goes against conventional thinking, which says that a large power output is only possible by building bigger fusion reactors.

    The largest fusion reactor currently under construction is the €16bn ITER facility in Cadarache, France.

    ITER Tokamak

    This will weigh about 23,000 tonnes when completed in the coming decade and consist of a deuterium–tritium plasma held in a 60 m-tall, doughnut-shaped “tokamak”. ITER aims to produce a fusion power gain (Q) of 10, meaning that, in theory, the reactor will emit 10 times the power it expends by producing 500 MW from 50 MW of input power. While ITER has a “major” plasma radius of 6.21 m, it is thought that an actual future fusion power plant delivering power to the grid would need a 9 m radius to generate 1 GW.

    Low power brings high performance

    The new study, led by Alan Costley from Tokamak Energy, which builds compact tokamaks, shows that smaller, lower-power, and therefore lower-cost reactors could still deliver a value of Q similar to ITER. The work focused on a key parameter in determining plasma performance called the plasma “beta”, which is the ratio of the plasma pressure to the magnetic pressure. By using scaling expressions consistent with existing experiments, the researchers show that the power needed for high fusion performance can be three or four times lower than previously thought.

    Combined with the finding on the size-dependence of Q, these results imply the possibility of building lower-power, smaller and cheaper pilot plants and reactors. “The consequence of beta-independent scaling is that tokamaks could be much smaller, but still have a high power gain,” David Kingham, Tokamak Energy chief executive, told Physics World.

    The researchers propose that a reactor with a radius of just 1.35 m would be able to generate 180 MW, with a Q of 5. This would result in a reactor just 1/20th of the size of ITER. “Although there are still engineering challenges to overcome, this result is underpinned by good science,” says Kingham. “We hope that this work will attract further investment in fusion energy.”

    Many challenges remain

    Howard Wilson, director of the York Plasma Institute at the University of York in the UK, points out, however, that the result relies on being able to achieve a very high magnetic field. “We have long been aware that a high magnetic field enables compact fusion devices – the breakthrough would be in discovering how to create such high magnetic fields in the tokamak,” he says. “A compact fusion device may indeed be possible, provided one can achieve high confinement of the fuel, demonstrate efficient current drive in the plasma, exhaust the heat and particles effectively without damaging material surfaces, and create the necessary high magnetic fields.”

    The work by Tokamak Energy follows an announcement late last year that the US firm Lockheed Martin plans to build a “truck-sized” compact fusion reactor by 2019 that would be capable of delivering 100 MW. However, the latest results from Tokamak Energy might not be such bad news for ITER. Kingham adds that his firm’s work means that, in principle, ITER is actually being built much larger than necessary – and so should outperform its Q target of 10.

    The research is published in Nuclear Fusion.

    See the full article here.

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  • richardmitnick 8:36 pm on December 8, 2014 Permalink | Reply
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    From PPPL: “Monumental effort: How a dedicated team completed a massive beam-box relocation for the NSTX upgrade” 


    December 8, 2014
    By John Greenwald

    Your task: Take apart, decontaminate, refurbish, relocate, reassemble, realign and reinstall a 75-ton neutral beam box that will add a second beam box to the National Spherical Torus Experiment-Upgrade (NSTX-U) and double the experiment’s heating power. Oh, and while you’re at it, hoist the two-story tall box over a 22-foot wall.

    Members of the “Beam Team” faced those challenges when moving the huge box from the Tokamak Fusion Test Reactor (TFTR) cell to the NSTX-U cell. The task required all the savvy of the PPPL engineers and technicians who make up the veteran team. “They’re a tight-knit group that really knows what they’re doing,” said Mike Williams, director of engineering and infrastructure and associate director of PPPL and a former member of the team himself.

    The second box is one of the two major components of the upgrade that will make NSTX-U the most powerful spherical tokamak fusion facility in the world when construction is completed early next year. The new center stack that serves as the other component will double the strength and duration of the magnetic field that controls the plasma that fuels fusion reactions.

    The two new components will work together hand-in-glove. The stronger magnetic field will increase the confinement time for the plasma while the second beam box performs double-duty. Its beams will raise the temperature of the plasma and will help to maintain a current in the plasma to demonstrate that future tokamaks can operate in a continuous condition known as a “steady state.” The second box is “an absolutely crucial part of the upgrade,” said Masayuki Ono, project director for the NSTX-U.

    PPPL Tokamak
    PPPL Tokamak

    Work began in 2009

    Work on the second beam box began in 2009 when technicians clad in protective clothing dismantled and decontaminated the box as it sat in the TFTR test cell. While the box had used radioactive tritium to heat the plasma in TFTR, no tritium will be used in NSTX-U experiments.

    The decontamination took huge effort, said Tim Stevenson, who led the beam box project. Workers wearing protective garb used cloths, Windex and sprayers with deionized water to clean every part of the box by hand, and went over each part as many as 50 separate times. The cloths were then packaged and shipped to a Utah radiation-waste disposal site.

    Next came the task of moving the beam box and its cleaned and refurbished components out of the TFTR area and into the NSTX-U test cell next door. But how do you get something so massive to budge?

    The Beam Team solved the problem with air casters, said Ron Strykowsky, who heads the NSTX-U upgrade program. Using a ceiling crane, workers lifted the box onto the casters, which floated the load on a cushion of air just above the floor, enabling forklifts to tow it. Technicians then removed some hardware from the large doorway between the two test cells so the beam box could get through.

    The doorway led to a section of the NSTX-U area that is separated from the vacuum vessel by a 22-foot shield wall — a barrier too high for the box and its lid to clear when suspended by sling from a crane. Workers surmounted the problem by first lifting the box and then the lid, which had been removed during the decontamination process. The parts cleared the wall and sailed over the vacuum vessel before coming to rest on the test cell floor. The vessel itself was wrapped in plastic to prevent contamination from any tritium that might still be in the box and the lid as they swung by overhead.

    “Like rebuilding a ship in a bottle”

    The beam box was now ready to be reassembled and reinstalled. But carving out room for all the parts and equipment, including power supplies, cables, and cooling water pipes, proved difficult. “There were so many conflicting demands for space that it was like rebuilding a ship in a bottle,” Stevenson said, citing a remark originally made by engineer Larry Dudek, who heads the center stack upgrade project. “There was no existing footprint,” Stevenson said. “We had to make our own footprint.”

    Technicians needed to cut a port into the vacuum vessel for the beam to pass through. But the supplier-built unit that connected the box to the vessel left too much space between the unit and this new port, requiring the Welding Shop to fill in the gap. “The Welding Shop saved the port,” Stevenson said.

    Still another challenge called for ensuring that the beam would enter the plasma at precisely the angle that NSTX-U specifications required. Complicating this task was the test cell’s uneven floor, which meant that the position of the box also had to be adjusted. To align the beam, engineers used measurements to derive a bull’s-eye on the inside of the vessel; technicians then used laser technology to zero in on the target. The joint effort aligned the beam to within 80 thousands of an inch of the target.

    Installing power supplies

    Left to complete was installation of power supplies, a task accomplished earlier this year. The job called for bringing three orange high-voltage enclosures — the source of the power — up from a basement area and into the test cell through a hatch in the floor. Taken together, the two NSTX-U beam boxes will have the capacity to put up to 18 megawatts of power into the plasma, enough to briefly light some 20,000 homes.

    When asked to name the greatest challenge the project encountered, Stevenson replied, “The whole thing was fraught with challenges and difficulties. It was a monumental team effort that took a great deal of preparation. And when it was show-time, everyone showed up.”

    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.

  • richardmitnick 9:08 pm on March 31, 2014 Permalink | Reply
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    From Argonne Lab via PPPL: “Plasma Turbulence Simulations Reveal Promising Insight for Fusion Energy” 

    March 31, 2014
    By Argonne National Laboratory

    With the potential to provide clean, safe, and abundant energy, nuclear fusion has been called the “holy grail” of energy production. But harnessing energy from fusion, the process that powers the sun, has proven to be an extremely difficult challenge.

    Simulation of microturbulence in a tokamak fusion device. (Credit: Chad Jones and Kwan-Liu Ma, University of California, Davis; Stephane Ethier, Princeton Plasma Physics Laboratory)

    Scientists have been working to accomplish efficient, self-sustaining fusion reactions for decades, and significant research and development efforts continue in several countries today.

    For one such effort, researchers from the Princeton Plasma Physics Laboratory (PPPL), a DOE collaborative national center for fusion and plasma research in New Jersey, are running large-scale simulations at the Argonne Leadership Computing Facility (ALCF) to shed light on the complex physics of fusion energy. Their most recent simulations on Mira, the ALCF’s 10-petaflops Blue Gene/Q supercomputer, revealed that turbulent losses in the plasma are not as large as previously estimated.


    Good news

    This is good news for the fusion research community as plasma turbulence presents a major obstacle to attaining an efficient fusion reactor in which light atomic nuclei fuse together and produce energy. The balance between fusion energy production and the heat losses associated with plasma turbulence can ultimately determine the size and cost of an actual reactor.

    “Understanding and possibly controlling the underlying physical processes is key to achieving the efficiency needed to ensure the practicality of future fusion reactors,” said William Tang, PPPL principal research physicist and project lead.

    Tang’s work at the ALCF is focused on advancing the development of magnetically confined fusion energy systems, especially ITER, a multi-billion dollar international burning plasma experiment supported by seven governments including the United States.

    Currently under construction in France, ITER will be the world’s largest tokamak system, a device that uses strong magnetic fields to contain the burning plasma in a doughnut-shaped vacuum vessel. In tokamaks, unavoidable variations in the plasma’s ion temperature drive microturbulence, which can significantly increase the transport rate of heat, particles, and momentum across the confining magnetic field.

    “Simulating tokamaks of ITER’s physical size could not be done with sufficient accuracy until supercomputers as powerful as Mira became available,” said Tang.

    To prepare for the architecture and scale of Mira, Tim Williams of the ALCF worked with Tang and colleagues to benchmark and optimize their Gyrokinetic Toroidal Code – Princeton (GTC-P) on the ALCF’s new supercomputer. This allowed the research team to perform the first simulations of multiscale tokamak plasmas with very high phase-space resolution and long temporal duration. They are simulating a sequence of tokamak sizes up to and beyond the scale of ITER to validate the turbulent losses for large-scale fusion energy systems.

    Decades of experiments

    Decades of experimental measurements and theoretical estimates have shown turbulent losses to increase as the size of the experiment increases; this phenomenon occurs in the so-called Bohm regime. However, when tokamaks reach a certain size, it has been predicted that there will be a turnover point into a Gyro-Bohm regime, where the losses level off and become independent of size. For ITER and other future burning plasma experiments, it is important that the systems operate in this Gyro-Bohm regime.

    The recent simulations on Mira led the PPPL researchers to discover that the magnitude of turbulent losses in the Gyro-Bohm regime is up to 50% lower than indicated by earlier simulations carried out at much lower resolution and significantly shorter duration. The team also found that transition from the Bohm regime to the Gyro-Bohm regime is much more gradual as the plasma size increases. With a clearer picture of the shape of the transition curve, scientists can better understand the basic plasma physics involved in this phenomenon.

    “Determining how turbulent transport and associated confinement characteristics will scale to the much larger ITER-scale plasmas is of great interest to the fusion research community,” said Tang. “The results will help accelerate progress in worldwide efforts to harness the power of nuclear fusion as an alternative to fossil fuels.”

    This project has received computing time at the ALCF through DOE’s Innovative and Novel Computational Impact on Theory and Experiment (INCITE) program. The effort was also awarded pre-production time on Mira through the ALCF’s Early Science Program, which allowed researchers to pursue science goals while preparing their GTC-P code for Mira.

    See the full article here.

    Princeton Plasma Physics Laboratory is a U.S. Department of Energy national laboratory managed by Princeton University.

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  • richardmitnick 6:33 pm on March 20, 2014 Permalink | Reply
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    From Oak Ridge via PPPL: “The Bleeding ‘Edge’ of Fusion Research” 

    March 20, 2014

    Few problems have vexed physicists like fusion, the process by which stars fuel themselves and by which researchers on Earth hope to create the energy source of the future.

    By heating the hydrogen isotopes tritium and deuterium to more than five times the temperature of the Sun’s surface, scientists create a reaction that could eventually produce electricity. Turns out, however, that confining the engine of a star to a manmade vessel and using it to produce energy is tricky business.

    Big problems, such as this one, require big solutions. Luckily, few solutions are bigger than Titan, the Department of Energy’s flagship Cray XK7 supercomputer managed by the Oak Ridge Leadership Computing Facility.


    Inside Titan

    Titan allows advanced scientific applications to reach unprecedented speeds, enabling scientific breakthroughs faster than ever with only a marginal increase in power consumption. This unique marriage of number-crunching hardware enables Titan, located at Oak Ridge National Laboratory (ORNL), to reach a peak performance of 27 petaflops to claim the title of the world’s fastest computer dedicated solely to scientific research.

    PPPL fusion code

    And fusion is at the head of the research pack. In fact, a team led by Princeton Plasma Physics Laboratory’s (PPPL’s) C.S. Chang increased the performance of its fusion XGC1 code fourfold on Titan using its GPUs and CPUs, compared to its previous CPU-only incarnation after a 6-month performance engineering period during which the team tweaked its code to best take advantage of Titan’s revolutionary hybrid architecture.

    “In nature, there are two types of physics,” said Chang. The first is equilibrium, in which changes happen in a “closed” world toward a static state, making the calculations comparatively simple. “This science has been established for a couple hundred years,” he said. Unfortunately, plasma physics falls in the second category, in which a system has inputs and outputs that constantly drive the system to a nonequilibrium state, which Chang refers to as an “open” world.

    Most magnetic fusion research is centered on a tokamak, a donut-shaped vessel that shows the most promise for magnetically confining the extremely hot and fragile plasma. Because the plasma is constantly coming into contact with the vessel wall and losing mass and energy, which in turn introduces neutral particles back into the plasma, equilibrium physics generally don’t apply at the edge and simulating the environment is difficult using conventional computational fluid dynamics.

    TFTR at PPPL Tokamak Fusion Test Reactor at Princeton Plasma Physics Laboratory Image Credit: Princeton.

    Another major reason the simulations are so complex is their multiscale nature. The distance scales involved range from millimeters (what’s going on among the gyrating particles and turbulence eddies inside the plasma itself) to meters (looking at the entire vessel that contains the plasma). The time scales introduce even more complexity, as researchers want to see how the edge plasma evolves from microseconds in particle motions and turbulence fluctuations to milliseconds and seconds in its full evolution. Furthermore, these two scales are coupled. “The simulation scale has to be very large, but still has to include the small-scale details,” said Chang.

    And few machines are as capable of delivering in that regard as is Titan. “The bigger the computer, the higher the fidelity,” he said, simply because researchers can incorporate more physics, and few problems require more physics than simulating a fusion plasma.

    On the hunt for blobs

    Studying the plasma edge is critical to understanding the plasma as a whole. “What happens at the edge is what determines the steady fusion performance at the core,” said Chang. But when it comes to studying the edge, “the effort hasn’t been very successful because of its complexity,” he added.

    Chang’s team is shedding light on a long-known and little-understood phenomenon known as “blobby” turbulence in which formations of strong plasma density fluctuations or clumps flow together and move around large amounts of edge plasma, greatly affecting edge and core performance in the DIII-D tokamak at General Atomics in San Diego, CA. DIII-D-based simulations are considered a critical stepping-stone for the full-scale, first principles simulation of the ITER plasma edge. ITER is a tokamak reactor to be built in France to test the science feasibility of fusion energy.


    The phenomenon was discovered more than 10 years ago, and is one of the “most important things in understanding edge physics,” said Chang, adding that people have tried to model it using fluids (i.e., equilibrium physics quantities). However, because the plasma inhabits an open world, it requires first-principles, ab-initio simulations. Now, for the first time, researchers have verified the existence and modeled the behavior of these blobs using a gyrokinetic code (or one that uses the most fundamental plasma kinetic equations, with analytic treatment of the fast gyrating particle motions) and the DIII-D geometry.

    This same first-principles approach also revealed the divertor heat load footprint. The divertor will extract heat and helium ash from the plasma, acting as a vacuum system and ensuring that the plasma remains stable and the reaction ongoing.

    These discoveries were made possible because the team’s XGC1 code exhibited highly efficient weak and strong scalability on Titan’s hybrid architecture up to the full size of the machine. Collaborating with Ed D’Azevedo, supported by the OLCF and by the DOE Scientific Discovery through Advanced Computing (SciDAC) project Center for Edge Physics Simulation (EPSi), along with Pat Worley (ORNL), Jianying Liand (PPPL) and Seung-Hoe Ku (PPPL) also supported by EPSi, this team optimized its XGC1 code for Titan’s GPUs using the maximum number of nodes, boosting performance fourfold over the previous CPU-only code. This performance increase has enormous implications for predicting fusion energy efficiency in ITER.

    Full-scale simulations

    “We can now use both the CPUs and GPUs efficiently in full-scale production simulations of the tokamak plasma,” said Chang.

    Furthermore, added Chang, Titan is beginning to allow the researchers to model physics that were just a year ago out of reach altogether, such as electron-scale turbulence, that were out of reach altogether as little as a year ago. Jaguar—Titan’s CPU-only predecessor— was fine for ion-scale edge turbulence because ions are both slower and heavier than electrons (for which the computing requirement is 60 times greater), but fell seriously short when it came to calculating electron-scale turbulence. While Titan is still not quite powerful enough to model electrons as accurately as Chang would like, the team has developed a technique that allows them to simulate electron physics approximately 10 times faster than on Jaguar.

    And they are just getting started. The researchers plan on eventually simulating the full volume plasma with electron-scale turbulence to understand how these newly modeled blobs affect the fusion core, because whatever happens at the edge determines conditions in the core. “We think this blob phenomenon will be a key to understanding the core,” said Chang, adding, “All of these are critical physics elements that must be understood to raise the confidence level of successful ITER operation. These phenomena have been observed experimentally for a long time, but have not been understood theoretically at a predictable confidence level.”

    Given the team can currently use all of Titan’s more that 18,000 nodes, a better understanding of fusion is certainly in the works. A better understanding of blobby turbulence and its effects on plasma performance is a significant step toward that goal, proving yet again that few tools are more critical than simulation if mankind is to use the engines of stars to solve its most pressing dilemma: clean, abundant energy.

    See the full article here.

    Princeton Plasma Physics Laboratory is a U.S. Department of Energy national laboratory managed by Princeton University.

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  • richardmitnick 8:12 pm on March 18, 2014 Permalink | Reply
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    From PPPL: “PPPL extends system for suppressing instabilities to long-pulse experiments on KSTAR” 

    March 18, 2014
    John Greenwald

    PPPL collaborations have been instrumental in developing a system to suppress instabilities that could degrade the performance of a fusion plasma. PPPL has built and installed such a system on the DIII-D tokamak that General Atomics operates for the U.S. Department of Energy in San Diego and on the Korea Superconducting Tokamak Advanced Research (KSTAR) facility in South Korea — and now is revising the KSTAR design to operate during extended plasma experiments. Suppressing instabilities will be vital for future fusion facilities such as ITER, the huge international project under construction in France.

    A look into the microwave launcher showing the steering mirrors that guide the beam into the plasma (Photo by PPPL)

    The system developed on DIII-D and then installed on KSTAR aims high-power microwave beams at instabilities called islands and generates electrical current that eliminates the islands. The process links software-controlled mirrors to detection equipment, creating a system that can respond to instabilities and suppress them within milliseconds. “It works like a scalpel that removes the island,” said PPPL physicist Raffi Nazikian, the head of the Laboratory’s collaboration with DIII-D.

    Revising the unit on KSTAR calls for adding a water-cooling system to keep the mirrors that direct the high-power microwaves into the plasma from overheating. KSTAR’s superconducting magnets can confine the plasma for up to 300 seconds during long-pulse experiments that reach temperatures far hotter than the 15-million degree Celsius core of the sun. “Once you get beyond 10 seconds you have to remove the heat as you put it in,” said PPPL engineer Robert Ellis, who designed the copper and copper-and-steel mirrors.

    Ellis was part of a team of PPPL physicists and engineers who worked closely with their counterparts at General Atomics to develop the original system on DIII-D. PPPL Physicist Egemen Kolemen, an expert in plasma control, created much of the software that automatically steers the mirrors and directs the microwave beams to their target. PPPL engineer Alexander Nagy also shared responsibility for the system, providing onsite support in San Diego.

    The microwave beams not only remove instabilities, but enable researchers to mimic the way that the alpha particles produced by fusion reactions will heat the plasma in ITER. While current heating methods typically heat the ions in plasma, these microwave beams act on the electrons instead. This process parallels what will happen in ITER. “By putting microwave power into the electrons,” Nazikian said, “we can experimentally simulate and study how a fusion plasma will be heated in ITER.”

    The revised KSTAR unit will extend such research to long-pulse plasma experiments when work on the water-cooled mirrors is completed later this year.

    See the full article here.

    Princeton Plasma Physics Laboratory is a U.S. Department of Energy national laboratory managed by Princeton University.

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  • richardmitnick 10:15 am on March 3, 2014 Permalink | Reply
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    From PPPL via DOE Pulse: “Celebrating the 20th anniversary of the tritium shot heard around the world” 

    DOE Pulse

    March 3, 2014

    No Writer Credit

    Tensions rose in the U.S. Department of Energy’s (DOE) Princeton Plasma Physics Laboratory (PPPL) as the seconds counted down. At stake was the first crucial test of a high-powered mixture of fuel for producing fusion energy. As the control-room clock reached “zero,” a flash of light on a closed-circuit television monitor marked a historic achievement: A world-record burst of more than 3 million watts of fusion energy — enough to momentarily light some 3,000 homes — fueled by the new high-powered mixture. The time was 11:08 p.m. on Thursday, Dec. 9, 1993.

    “There was a tremendous amount of cheering and clapping,” recalled PPPL physicist Rich Hawryluk, who headed the Tokamak Fusion Test Reactor (TFTR), the huge magnetic fusion facility — or tokamak — that produced the historic power. “People had been on pins and needles for a long time and finally it all came together.” It did so again the very next day when TFTR shattered the mark by creating more than six million watts of fusion energy.

    pppl tokamak
    PPPL Tokamak

    The achievements generated headlines around the world and laid the foundation for the development of fusion energy in facilities such as ITER, the vast international experiment being built in France to demonstrate the feasibility of fusion power. The results delivered “important scientific confirmation of the path we are taking toward ITER,” said physicist Ed Synakowski, a PPPL diagnostics expert during the experiments and now associate director of the Office of Science for Fusion Energy Sciences at DOE. “I felt an important shift in the understanding of fusion’s likely reality with those experiments.”

    The breakthroughs proved the practicality of combining equal amounts of the hydrogen isotopes deuterium and its radioactive cousin tritium — the same combination that will be used in ITER and future fusion power plants — to form the superhot, charged plasma gas that fuels fusion reactions. The deuterium-tritium (D-T) mix produced some 150 times more power than a reaction fueled solely by deuterium, long the stand-alone ingredient in tokamak experiments, or “shots.”

    “This was the first test with equal parts D-T and it was technically quite challenging,” said Michael Zarnstorff, a task-force leader during the experiments and now deputy director for research at PPPL. “What we did marked a huge advance in integrating tritium into fusion facilities.”

    Gained insights included precise measurement of the confinement and loss of alpha particles that fusion reactions release along with energetic neutrons. Good confinement of the alpha particles is critically important since they are to serve as the primary means of heating the plasma in ITER, and thereby producing a self-sustaining fusion reaction, or “burning plasma.”

    Exciting journey

    The historic shots capped years of intense preparation for tritium operations, which ran until TFTR was decommissioned in 1997 after setting more records and producing reams of new knowledge. “The journey to tritium was at least as exciting as the first experiments,” said former PPPL Director Ronald Davidson, who led the Laboratory during the tritium years. “It was an enormous technical undertaking and one of my greatest elements of pride in the PPPL staff was that the preparations were so good and so thorough that the tritium shots were successful early on in the D-T campaign.”

    The preparations mobilized physicists, engineers and staffers throughout the Laboratory. “The absolute top priority was to demonstrate that one could carry out the tritium experiments safely,” said former Deputy Director Dale Meade. “Everyone focused on this mission as we went through a step-by-step construction and checkout of the tritium systems with rigorous adherence to procedures and strong oversight by DOE.”

    Leaders of this effort included Jerry Levine, now head of the Environment, Safety, Health & Security Department at PPPL, and John DeLooper, who heads the Best Practices and Outreach Department. Levine’s team launched an environmental assessment under the National Environmental Policy Act in 1989 and received DOE and state approval in 1992. “The purpose was to show that there would be no significant environmental impact as a result of tritium operations,” Levine noted. DeLooper’s team double-checked everything from operator training to preparations for storing and moving the tritium gas, which subsequently arrived in stainless steel containers from the Savannah River National Laboratory in South Carolina.

    In the towering TFTR test cell, engineers readied the three-story high, 695-ton tokamak to operate with tritium. Key tasks included adding more shielding, checking all major systems against possible failures and ensuring that every diagnostic device worked. “The major challenge was to bring everything on line so that failures didn’t happen,” said Mike Williams, the head of engineering at PPPL and also deputy head of TFTR at the time.

    Yet nothing could be certain until the experiment began. “The whole world was going to show up and we had lots of opportunity to fall on our faces,” said engineer Tim Stevenson, who headed the neutral beam operations that heated the plasma to temperatures of more than 100 million degrees centigrade during the shots. “All the instruments were tuned up,” Stevenson said, “but we still had to play the symphony.”

    Keeping the local community informed was another high-priority. PPPL leaders held open houses, met with local executives and government officials and conducted two public hearings before the arrival of tritium. Attendees at one hearing included a local college class that arrived at the urging of its professor.

    Scientists from around the world

    By the day of December 9, press coverage and Laboratory outreach had made PPPL a focus of attention. “Scientists from around the world flew in to witness the experiment,” recalled Rich Hawryluk. More than 100 local visitors flocked to the PPPL auditorium, where a closed-circuit TV feed displayed the control room and Ron Davidson and Dale Meade briefed the audience on unfolding developments. PPPL staffers and their families crowded around the viewing area that overlooked the control room.

    Reporters from several major newspapers covered the event. Also there was Mark Levenson, a reporter from New Jersey public TV station NJN whom the Lab hired to produce a video that subsequently received worldwide exposure.

    The source of all this excitement was surprisingly small: Just six-millionths of a gram of tritium was consumed that night in the shot that made global news. “Such tiny amounts generate huge energy because of the formula E = mc2” explained Charles Gentile, the head of tritium systems at PPPL. The celebrated Einstein equation states that the amount of energy in a body equals the mass of that body times the speed of light squared — an enormous number since light travels at 186,000 miles per second.

    The media seemed as eager as the scientists to watch the famed formula work. “The press people were enormously excited,” said now-retired physicist Ken Young, who headed the PPPL diagnostics department and led efforts to measure the confinement and loss of alpha particles during the experiments. “These reporters were seeing science as it happens and kept waiting for the shot.”

    Also anxiously waiting were more than 100 scientists, engineers and invited guests inside the control room, which normally held about 40 people. All sported red passes that the Laboratory gave to PPPL staffers and guests from DOE and institutions that collaborated on TFTR. “Everybody who could be in there was in there,” recalled Forrest Jobes, a now-retired physicist who kept those in the rear of the L-shaped room abreast of what was happening.

    Calling the shots

    Up front, physicist Jim Strachan was too intent on his job to be caught up in the exuberance. His task was literally to call the shots — to decide how much heating power to use, for example, and when to start the countdown. “Everyone in the group was out to get the most D-T power from reproducible shots,” the now-retired Strachan recalled. “I felt a lot of responsibility and didn’t want to foul up.”

    All eyes followed a closed-circuit TV monitor that displayed a neutron-sensitive scintillator screen in the TFTR test cell that glowed when struck by the neutrons that a D-T shot produced. Artfully covering this test-cell screen was a cardboard poster — designed by PPPL graphic artist Gregory Czechowicz at the behest of Dale Meade — with holes cut into the shape of a light bulb and letters spelling “Fusion Power.” Engineer George Renda designed the scintillator itself. A flash of light from the bulb and the letters in the 3-foot-by-3-foot poster that covered the screen signaled a successful shot. “We came to really count on that image,” said Ed Synakowski. “No need to wait for the computer system to process the data.”

    But there still was plenty of waiting while a series of hardware glitches dragged out the schedule. “Many people in the audience thought we were doing this intentionally to increase the suspense,” Meade recalled.

    By 11 p.m. the problems were solved — setting the stage for the record-breaking shot at 11:08 signaled by the brightly lit light bulb and “Fusion Power” sign on the TV monitor. The control room erupted in jubilation over the shot, which produced 3.8 million watts of power. The excitement reached even the normally staid control-room log, where an operator noted the historic event with the exclamation, “EEYAH”!

    On that high note the experiments ended and the control room opened for press interviews. NJN reporter Levenson returned to his studio to assemble a video news release that he uploaded to a satellite for worldwide distribution, sending the piece off at about 4 a.m. Key parts of the footage — including the control-room jubilation — were shown on nationwide newscasts the following evening.
    Looking back at these events, Hawryluk reflected on the sense of excitement, anticipation and relief that came with them. “We had worked so hard to finally get to that stage and we had done it,” he said. “That night on December 9 established a research capability that has enabled us to pursue a whole host of opportunities to advance the development of fusion energy.”

    See the full article here.

    DOE Pulse highlights work being done at the Department of Energy’s national laboratories. DOE’s laboratories house world-class facilities where more than 30,000 scientists and engineers perform cutting-edge research spanning DOE’s science, energy, National security and environmental quality missions. DOE Pulse is distributed twice each month.

    Princeton Plasma Physics Laboratory is a U.S. Department of Energy national laboratory managed by Princeton University.

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  • richardmitnick 4:45 pm on November 25, 2013 Permalink | Reply
    Tags: , , , , , , Tokamak Technology   

    From PPPL- “Multinational achievement: PPPL collaborates on record fusion plasma in tokamak in China” 

    November 25, 2013
    John Greenwald

    A multinational team led by Chinese researchers in collaboration with U.S. and European partners has successfully demonstrated a novel technique for suppressing instabilities that can cut short the life of controlled fusion reactions. The team, headed by researchers at the Institute of Plasma Physics in the Chinese Academy of Sciences (ASIPP), combined the new technique with a method that the U.S. Department of Energy’s Princeton Plasma Physics Laboratory (PPPL) has developed for protecting the walls that surround the hot, charged plasma gas that fuels fusion reactions.

    Interior view of EAST tokamak(Photo by Institute of Plasma Physics, Chinese Academy of Sciences )

    The record-setting results of the tests, conducted on the Experimental Advanced Superconducting Tokamak (EAST) in Hefei, China, could mark a key step in the worldwide effort to develop fusion as a clean and abundant source of energy for generating electricity. “This is a very good example of multinational collaboration on EAST,” said ASIPP Director Jiangang Li. “I very much appreciate the effort of our collaborators.”

    First reporting the results was a paper published online in the November issue of the journal Nature Physics. U.S co-authors included PPPL physicists Jon Menard and Rajesh Maingi, who headed the wall-conditioning effort, and General Atomics physicist Gary Jackson, a plasma-control expert who helped draft the paper.

    The findings could hold particular promise for developers of future fusion facilities such as ITER, the international experiment under construction in France. Controlling instabilities that erupt at the edge of the plasma will be crucial to the success of the huge donut-shaped ITER tokamak, which is designed to demonstrate the feasibility of fusion power.

    The EAST experiments set a record for the duration of what is called an H-mode, or high-confinement plasma — the type that will be employed in ITER and other future tokamaks. To achieve this duration, the EAST team beamed what are known as “lower hybrid wave current drive” microwaves into the plasma. The antenna-launched beams reshaped the magnetic field lines confining the plasma and suppressed instabilities at the edge of the gas near the interior walls of the tokamak. Controlling these fast-growing instabilities, called “edge localized modes” (ELMs), produced a record life span of more than 30 seconds for the H-mode plasma.

    These results suggested a potent new method for suppressing ELMS to create an extended, or long-pulse, plasma. Many methods already exist. Among them are the use of external magnetic coils to alter the field lines that enclose the plasma, and the injection of pellets of deuterium fuel into the plasma during experiments.

    Contributing to the EAST results was the PPPL-designed wall treatment, which coated the plasma-facing walls of the tokamak with the metal lithium and inserted lithium granules into experiments to keep the coating fresh. The silvery metal absorbed stray plasma particles and kept impurities from entering the core of the plasma and halting fusion reactions. “When lithium has been used to coat the walls of fusion devices, higher plasma temperature, pressure, and confinement have been achieved,” PPPL physicists Menard and Maingi said in an interview.

    “This was good physics,” Jackson of General Atomics said of the experiments, noting that long-pulse plasmas will be required for fusion power plants to generate electricity.

    Combining microwave beams for ELMs suppression with the advanced lithium wall treatment could thus provide a fruitful new direction for fusion-energy development. This combination of techniques, the Nature Physics paper said, offers “an attractive regime for high-performance, long-pulse operations.”

    See the full article here.

    Princeton Plasma Physics Laboratory is a U.S. Department of Energy national laboratory managed by Princeton University.

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  • richardmitnick 1:04 pm on March 29, 2013 Permalink | Reply
    Tags: , , , , , , Tokamak Technology   

    From PPPL Lab: “US ITER is a strong contributor in plan to enhance international sharing of prime ITER real estate” 

    March 28, 2013
    Lynne Degitz

    “When the ITER experimental fusion reactor begins operation in the 2020s, over 40 diagnostic tools will provide essential data to researchers seeking to understand plasma behavior and optimize fusion performance. But before the ITER tokamak is built, researchers need to determine an efficient way of fitting all of these tools into a limited number of shielded ports that will protect the delicate diagnostic hardware and other parts of the machine from neutron flux and intense heat. A port plug integration proposal developed with the US ITER diagnostics team has helped the international ITER collaboration arrive at a clever solution for safely housing all of the tokamak diagnostic devices.

    Iter Icon


    ‘Before horizontal or vertical modules were proposed, diagnostic teams were not constrained to any particular design space. When we started working on this, we suggested that there be some type of modular approach,’ said Russ Feder, a US ITER diagnostics contributor and Senior Mechanical Engineer at Princeton Plasma Physics Laboratory. ‘Originally, we proposed four horizontal drawers for each port plug. But then analysis of electromagnetic forces on these horizontal modules showed that forces were too high and the project switched to the three vertical modules.’”

    The proposal has been formalized by two ITER procurement agreements in late 2012 between US ITER, based at Oak Ridge National Laboratory, and the ITER Organization; other ITER partners are expected to make similar agreements this year.”

    PPPL’s Russell Feder, left, and David Johnson developed key features for a modular approach to housing the extensive diagnostic systems that will be installed on the ITER tokamak. (Photo credit: Elle Starkman/PPPL Office of Communications)

    See the full article here.

    Princeton Plasma Physics Laboratory is a U.S. Department of Energy national laboratory managed by Princeton University.

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  • richardmitnick 5:09 pm on December 21, 2012 Permalink | Reply
    Tags: , , , , Tokamak Technology   

    From PPPL: “PPPL teams with South Korea on the forerunner of a commercial fusion power station” 

    December 21, 2012
    John Greenwald

    “The U.S. Department of Energy’s Princeton Plasma Physics Laboratory (PPPL) has joined forces with researchers in South Korea to develop a conceptual design for a pioneering fusion facility in that Asian nation. The proposed device, called K-DEMO, could be completed in the mid-to-late 2030s as the final step before construction of a commercial fusion power plant that would produce clean and abundant energy for generating electricity.

    Schematic sketch of the proposed K-DEMO fusion facility.(Photo credit: Courtesy of South Korea’s National Fusion Research Institute.)

    South Korea’s National Fusion Research Institute (NFRI) will fund PPPL’s initial collaboration, which will run for six months, beginning in January, and could be extended.

    PPPL will explore cutting-edge designs and technologies that could benefit the U.S. fusion program, and South Korea will gain access to the Laboratory’s deep experience in designing and engineering fusion facilities. These include the National Spherical Torus Experiment (NSTX), PPPL’s leading fusion experiment, which is undergoing a major upgrade.

    NSTX at PPPL

    K-DEMO will be comparable in size to ITER, a seven-story tokamak that the European Union, the United States, South Korea and four other nations are building in Cadarache, France. ITER is to produce 500 million watts of fusion power for 500 seconds by the late 2020s to showcase the feasibility of fusion energy. K-DEMO, by contrast, is to produce some 1 billion watts of power for several weeks on end. “K-DEMO should be just a small step away from a commercial plant in technology and performance,” said Neilson.



    iter tokamak
    Iter paints a bigger picture, but K-Demo has a much larger goal.

    See the full PPPL article here.

    Princeton Plasma Physics Laboratory is a U.S. Department of Energy national laboratory managed by Princeton University.

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