New Paths to Fusion Energy

A landmark plan for realizing fusion free energy and advancing plasma science

Physicist Nathan Ferraro with image from cover of report behind him. Photo and composite by Elle Starkman/PPPL Office of Communications.

Physicist Nathan Ferraro with prototype from comprehend of report behind him. (Photo and composite by Elle Starkman/PPPL Office of Communications.)

Creating and controlling on Earth the fusion free energy that powers the sunday and stars is a central goal of scientists around the world. Production of this condom, make clean and limitless energy could generate electricity for all humanity, and the possibility is growing closer to reality. A landmark report released by the American Physical Society Sectionalisation of Plasma Physics Community Planning Process has proposed immediate steps for the United States to take to accelerate U.S. evolution of this long-sought ability. The report also details opportunities for advancing our understanding of plasma physics and for applying that agreement to benefit society.

The written report, the Community Program for Fusion Energy and Discovery Plasma Sciences , delivered a major contribution to the long-range strategic plan that the U.S. Section of Energy's (DOE) Fusion Energy Sciences Advisory Committee (FESAC) released last Dec. That document, prepared by a FESAC subcommittee on which PPPL physicist Rajesh Maingi saturday, "provides a decade-long vision for the field of fusion energy and plasma scientific discipline, presenting a path to a promising hereafter of new scientific discoveries, industrial applications, and ultimately the timely commitment of fusion energy," the preface said.

The landmark community report "reflects the enthusiasm among the U.S. fusion and plasma physics community to take bold steps to make fusion energy a reality, to aggrandize our understanding of plasma physics, and to apply that understanding to do good society," said PPPL physicist Nathan Ferraro, a co-chair of the plan the community assembled over a twelvemonth.

The 199-folio document, put together with input from hundreds of U.South. scientists and engineers from many professional societies, makes numerous recommendations ranging from enabling construction of a fusion airplane pilot plant (FPP) that produces net electricity to advancing theory and modeling capabilities needed to understand and sustain called-for plasmas, in which the plasma is chiefly heated by fusion reactions, a chief goal of the research.

The report is designed to help the Fusion Energy Sciences Advisory Committee (FESAC) fulfill a U.S. Section of Energy charge for the evolution of a long-range strategy for the Fusion Energy Sciences plan of the DOE Office of Science. The document calls for partnerships with other offices and governmental agencies, as well as with private manufacture and international partners, to enact the total recommendations of the strategic programme.

A proven method for stabilizing efforts to bring fusion power to World

PPPL physicist Florian Laggner

Physicist Florian Laggner earlier the DIII-D tokamak with a figure from his paper. (Photo by Alessandro Bortolon. Blended by Elle Starkman/PPPL Office of Communications.)

All efforts to replicate in tokamak fusion facilities the fusion energy that powers the sun and stars must cope with transient rut bursts that can halt fusion reactions and damage the doughnut-shaped tokamaks. These bursts, called edge localized modes (ELMs), occur at the edge of hot, charged plasma gas when it kicks into high gear to fuel fusion reactions.

To foreclose such bursts, researchers at the DIII-D National Fusion Facility that General Atomics (GA)operates in San Diego previously pioneered the injection of ripples of magnetic fields into the plasma to cause heat to leak out controllably. Now PPPL scientists have adult a command scheme to optimize the levels of these fields for maximum functioning without ELMs.

The research, led by PPPL physicist Florian Laggner and developed on DIII-D with researchers from GA and other institutions, reveals a path to suppressing ELMs and maximizing fusion power on ITER, the international tokamak under structure in French republic that is designed to demonstrate the practicality of fusion energy.

The technique addresses the inherent conflict between optimizing fusion free energy and controlling ELMs. The scheme focuses on the "pedestal," the thin, dense layer of plasma near the edge of the tokamak that increases the pressure of the plasma and thus fusion ability. However, if the pedestal grows too loftier it can create ELM heat bursts past suddenly collapsing.

Then the key is controlling the height of the pedestal to maximize fusion power while preventing the layer from becoming so high that it triggers ELMs. The combination calls for real-time command of the process.

Advancing the arrival of fusion energy through improved agreement of fast plasma particles

Laura Xin Zhang

Physicist Laura Xin Zhang with figures from her paper. (Collage by Elle Starkman/PPPL Office of Communications.)

Unlocking the zig-zagging dance of hot, charged plasma particles that fuel fusion reactions tin can assist to harness on Earth the fusion energy that powers the dominicus and stars. An experimentalist and two theorists at PPPL accept worked together to develop a new algorithm, or set up of figurer rules, for tracking volatile particles — an algorithm that could advance the arrival of safe, clean and virtually limitless source of free energy.

"This is a success story about close interaction between theorists and experimentalists that shows what tin be washed," said Hong Qin, a principal theoretical physicist at PPPL. He and Yichen Fu, a theoretical graduate student whom he advises, collaborated on the algorithm with Laura Xin Zhang, an experimental graduate pupil and atomic number 82 author of a paper that reports the research.

The new algorithm helps track fast charged particles in the plasma. Such particles could, for instance, stem from the injection of loftier-energy neutral beams that are cleaved downward, or "ionized," in the plasma and collide with the main plasma particles.

"We care about this because nosotros desire to empathize how these fast particles influence the plasma," Zhang said. "We apply these particles to practice all sorts of things. They can estrus and drive current in the plasma. Sometimes they create plasma instabilities and sometimes they reduce them. Our simulations are all part of agreement how these particles conduct."

When Zhang first tried simulating the fast particles she ran into a problem. She used a classic algorithm that failed to conserve energy when the electrons in plasma collide with the ions, which are roughly 2,000-times heavier, in collisions akin to ping-pong balls bouncing off basketballs.

Conserving that free energy is disquisitional, said Qin. Otherwise, "the simulation cannot be trusted." He therefore devised an explicitly solvable algorithm that conserves the energy of the particles, which Zhang found worked better than the archetype algorithm but could non be proven theoretically. "I'thou an experimentalist at center, so I ran a bunch of simulations and did all kinds of numerical experiments and showed that the algorithm did work meliorate," she said.

Qin next handed the problem to graduate educatee Fu, who put together a clever mathematical proof of the correctness of the algorithm that could become a step to further solutions. "The algorithm nosotros developed is for a simplified model," Zhang said. "Just I am charging ahead and aiming to apply the new algorithm to new plasma physics issues."

Feeding fusion: hydrogen water ice pellets prove effective for fueling fusion plasmas

Physicist Oak Nelson

(Physicist Oak Nelson. (Photo and composite by Elle Starkman/PPPL Role of Communications.)

Researchers have establish that injecting pellets of hydrogen ice rather than puffing hydrogen gas improves fusion operation at the DIII-D National Fusion Facility, which Full general Atomics operates for the U.South. Section of Free energy. The studies by physicists based at PPPL and Oak Ridge National Laboratory (ORNL) compared the ii methods, looking alee to the fueling to be used in ITER, the international fusion experiment nether structure in France.

The research showed that icy pellets of hydrogen improve the temperature of the fusion plasma when compared with the gas-fueling method now typically used in doughnut-shaped fusion facilities called tokamaks. College temperatures are beneficial for the fusion reactions. The results on DIII-D are encouraging for ITER, which plans to use pellet injection to fuel its hot inner cadre.

The joint research effort on DIII-D compared the 2 fueling methods in loftier-performance plasmas planned for ITER. The experiments revealed a significantly higher pressure of plasma — a cardinal to fusion reactions — using hydrogen ice compared to gas injection when the rate of fueling is roughly evenly matched between the two methods.

"The fueling plays a big office in the border plasma operation," said Andrew "Oak" Nelson, a graduate student in the Program in Plasma Physics at Princeton University and outset author of the Nuclear Fusion article describing these results . The applied science for injecting the water ice pellets was developed past scientists at ORNL.

The inquiry besides demonstrates how graduate students can brand important contributions to fusion energy past working on these large national enquiry facilities. "For a graduate student to play an important role in this experimental written report on DIII-D is impressive," said Egemen Kolemen, a PPPL and Princeton University physicist who was an advisor for the project. "Oak's success shows how large fusion experiments provide meaning leadership opportunities for students and early on career scientists."

Permanent magnets alike to those on fridges could speed the evolution of fusion free energy

Schematic of stellarator and coauthors

Schematic of stellarator with plasma in xanthous and permanent magnets in red and bluish surrounded past simplified coils. Coauthors from left with image from paper behind them: PPPL Manager Steve Cowley, PPPL Chief Scientist Michael Zarnstorff, and Per Helander, Max Planck Establish of Plasma Physics. Background Paradigm of plasma in yellow and magnetic surface in blueish. (Schematic past Coaxing Zhu. Photograph and collage by Elle Starkman/PPPL Part of Communications. Groundwork Image of plasma in xanthous and magnetic surface in blue by Michael Drevlak.)

Permanent magnets much stronger than those used on refrigerators could speed the evolution of fusion free energy – the aforementioned energy produced past the sunday and stars. Such magnets could in principle profoundly simplify the design and production of twisty fusion facilities called stellarators, say scientists at PPPL and the Max Planck Establish for Plasma Physics in Deutschland. PPPL founder Lyman Spitzer Jr. invented the stellarator in the early on 1950s.

Most stellarators use a set of costly and complex twisted coils that spiral like stripes on a candy pikestaff to produce magnetic fields that shape and command the plasma that fuels fusion reactions. Refrigerator-like permanent magnets could produce the hard-to-create part of these essential fields, the researchers say, allowing simple, non-twisted coils to create the remaining part in place of the complex coils.

Simplifying stellarators, which run without the risk of damaging disruptions that more widely used tokamak fusion devices confront, can hold smashing appeal. "I am extremely excited about the use of permanent magnets to shape the plasma in stellarators," said Steve Cowley, PPPL director. "It leads to much simpler applied science design."

The novel idea for permanent magnets is an adjunct of a science fair project that Jonathan Zarnstorff, the son of PPPL Primary Scientist Michael Zarnstorff, put together in junior high school. Jonathan wanted to build a rail gun, a device that ordinarily uses loftier-voltage electric current to generate a magnetic field that can burn down a projectile. Merely the high-voltage electric current would be unsafe to use in a classroom.

The solution that begetter-and-son arrived at was to use rare globe permanent magnets to safely produce the magnetic field. Rare globe magnets take surprising and useful properties. Such magnets generate quite powerful fields for the magnets' small size, and they are almost unaffected by other fields nearby. The magnets could thus provide what physicists call the "poloidal" role of a spiraling stellarator field, while unproblematic round coils could provide the "toroidal" office that makes up the balance of the field.

PPPL is now developing permanent magnets with an exterior developer. The work could become the forerunner for a program that takes the run a risk out of designing and building these twisty machines.

Scientists propose method for eliminating damaging rut bursts in fusion device

Physicists Raffi Nazikian and Qiming Hu with figure from research backside them. (Photograph and collage by Elle Starkman/PPPL Office of Communications.)

Picture an airplane that can just climb to 1 or 2 altitudes afterwards taking off. That limitation would be similar to the plight facing scientists who seek to avoid instabilities that restrict the path to clean, safe and abundant fusion energy in doughnut-shaped tokamak facilities. Researchers at PPPL and Full general Atomics (GA) have published a breakthrough caption of this tokamak restriction and how it may be overcome.

Doughnut-shaped tokamaks are prone to intense bursts of heat and particles, chosen edge localized modes (ELMs) that can damage the reactor walls and must be controlled to develop reliable fusion power. Fortunately, scientists take learned to tame these ELMs past applying spiraling rippled magnetic fields to the surface of the plasma that fuels fusion reactions. Even so, the taming of ELMs requires specific weather condition that limit the operational flexibility of tokamak reactors.

Now, researchers at PPPL and GA have developed a model that, for the start fourth dimension, accurately reproduces the conditions for ELM suppression in the DIII-D National Fusion Facility that GA operates for the U.S. Department of Energyy. The model predicts the conditions under which ELM suppression should extend over a wider range of operating conditions in the tokamak than previously thought possible. The work presents of import predictions for how to optimize the effectiveness of ELM suppression in ITER, the massive international fusion device under construction in the south of France to demonstrate the feasibility of fusion power.

PPPL physicists Qiming Hu and Raffi Nazikian are the lead authors of a paper describing the model in Physical Review Letters . They note that nether normal weather the rippled magnetic field can simply suppress ELMs for very precise values of the plasma current that produces the magnetic fields that confine the plasma. The authors show how, by modifying the structure of the helical magnetic ripples practical to the plasma, ELMs should be eliminated over a wider range of plasma current with improved generation of fusion power. Hu said he believes the findings could provide ITER with the broad operational flexibility information technology will need to demonstrate the practicality of fusion energy. "This model could accept significant implications for suppressing ELMs in ITER," he said.

Return of the Hulk: Scientists observe surprising link to troublesome turbulence at the edge of fusion plasmas

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

Blobs can wreak havoc in plasma required for fusion reactions. This bubble-like turbulence swells upward at the edge of fusion plasmas and drains rut from the edge, limiting the efficiency of fusion reactions in doughnut-shaped tokamaks. Researchers at PPPL have now discovered a surprising correlation of the blobs with fluctuations of the magnetic field that confines the plasma fueling fusion reactions in the tokamak core.

"These results add a new aspect to our agreement of the heat loss at the border of the plasma in a tokamak," said physicist Stewart Zweben, lead author of a newspaper in Physics of Plasmas that editors have selected as a featured article. "This work as well contributes to our agreement of the physics of blobs, which can help to predict the performance of tokamak fusion reactors."

Researchers discovered the surprising link when re-analyzing experiments made in 2010 on PPPL's National Spherical Torus Experiment (NSTX) — the precursor of today's National Spherical Torus Experiment-Upgrade (NSTX-U). The blobs and fluctuations in the magnetic field develop in all tokamaks and have traditionally been seen as independent of each other.

The scientists then analyzed several possible causes of the unexpected correlation just could find no single compelling explanation. To empathise and command this phenomenon, Zweben said, further data assay and modeling volition have to exist done. Further investigation of the correlation and its function in the loss of oestrus from magnetic fusion reactors could help to produce on Earth the fusion energy that powers the sun and stars.

New model helps pave the way to bringing clean fusion energy downwards to Eart h

Physicist Juan Ruiz Ruiz at MIT. (Photo courtesy of Juan Ruiz Ruiz.)

Turbulence — the unruly swirling of fluid and air that mixes coffee and cream and can rattle airplanes in flight — causes heat loss that weakens efforts to reproduce on Globe the fusion that powers the sun and stars. Now scientists have modeled a key source of the turbulence plant in a fusion experiment at PPPL, paving the fashion for improved experiments to capture and control fusion energy.

The research, led by Juan Ruiz Ruiz while a graduate student at the Massachusetts Plant of Technology (MIT) who worked with PPPL researchers Walter Guttenfelder and Yang Ren, used state-of-the-art simulations to null-in on the source of the turbulence that produces estrus loss. The findings predicted results consistent with experiments on the National Spherical Torus Experiment (NSTX) fusion device at PPPL, pinpointing the source as microscopic turbulent eddies. Driving these eddies is the gradient, or variation, in the electron temperature in the core of the plasma, the so-chosen electron temperature gradient (ETG).

The findings confirmed theories of when ETG tin can be a main driver of electron turbulence, technically known every bit electron thermal send, that whips upwards the heat loss in spherical tokamaks such as NSTX. The consistency of the simulation with experimental data gives confidence "that the simulation contains the necessary physics to explain the loss of heat," said Ruiz Ruiz, now a postdoctoral research assistant at the University of Oxford and showtime author of a paper reporting the results in Plasma Physics and Controlled Fusion .

Understanding the source of electron thermal transport is a top priority for confining heat in future fusion facilities, and specially in spherical tokamaks, which lose most of their heat through such transport in high-functioning H-mode plasmas. Further research could confirm the source of this rut loss on the upgraded NSTX, called the NSTX-U, and the Mega Ampere Spherical Tokamak (MAST) in the United Kingdom, Ruiz Ruiz said. "That could demonstrate the ability of the simulations to accurately forecast the loss of heat — and therefore the functioning — of spherical tokamaks."

Building a star in a smaller jar

PPPL physicist Devon Battaglia with graphs illustrating fusion plasma in enhanced pedestal H-mode (Photo by Elle Starkman/PPPL Office of Communications.)

PPPL scientist have bettered their understanding of a promising method for improving the confinement of superhot fusion plasma within magnetic fields. Improved plasma confinement could enable construction of smaller and less expensive blazon of fusion reactor called a spherical tokamak, moving the earth closer to reproducing on World the fusion energy that powers the sunday and stars.

Creating the improved confinement is a condition called the enhanced pedestal (EP) H-mode, a variety of the high performance, or H-mode, plasma state that scientists take observed for decades in tokamaks around the world. This mode requires less heating to raise plasma to the superhot temperatures necessary for fusion reactions.

Scientists led by physicists at PPPL have discovered that EP H-mode improves upon H-mode in spherical tokamaks by lowering the density of the plasma edge. The reduced density occurs when small instabilities in the plasma edge eject relatively cold, depression-energy particles. With fewer cold particles to bump into, the hotter particles in the plasma are less likely to leak out.

"Every bit the higher energy particles stay in the plasma in larger quantities, they increase the pressure level in the plasma, feeding the instabilities that throw out colder particles and further lowering the edge density," said PPPL physicist Devon Battaglia, who led the inquiry projection. "Ultimately, the fortuitous interaction allows the plasma to stay hotter with the aforementioned heating and footling modify to the boilerplate plasma density.

"It's like calculation meliorate insulation to your house," Battaglia said. "The more the plasma holds on to its oestrus, the smaller you can make the device." Moreover, he added, "by taking the next leap in our agreement of how the EP H-style process comes near, we can have more conviction in being able to predict if it'south going to happen."

Beginning results of an upgraded experiment highlight the value of lithium for the cosmos of fusion energy

The squad that upgraded the LTX-β. (Photograph by Elle Starkman/PPPL Office of Communications.)

Lithium, the silver metal that powers smart phones and helps treat bipolar disorders, could play a significant role in the worldwide effort to harvest on Earth the safe, make clean and most limitless fusion free energy that powers the sun and stars. Start results of the extensively upgraded Lithium Tokamak Experiment-Beta (LTX-β) at PPPL demonstrate that the major enhancements operate every bit designed and amend the operation of the hot, charged plasma that will fuel futurity fusion reactors.

The three-yr upgrade turned what is now the LTX-β into a hotter, denser and more fusion-relevant device that will test how well coating all plasma-facing walls with liquid lithium can improve the confinement and increment the temperature of the plasma. "Nosotros accomplished many of our initial engineering goals," said physicist Drew Elliott of Oak Ridge National Laboratory, a major collaborator of the LTX-β on long-term consignment to PPPL who served as lead author of the kickoff results paper.

Key features of the LTX-β include a powerful neutral beam injector to estrus and fuel the plasma; a nearly doubled magnetic field compared with the previous device; and a twin evaporation system to fully coat liquid lithium on all the plasma-facing surfaces.

Operation of the beam matched well with predictions of the fraction of power that it would deposit into the plasma, rather than just shining through it. "We're looking to increase the power deposition toward 100% so that all the power we inject goes into the plasma," said Elliott.

The substantial enhancements aim to test whether the LTX-β can better plasma performance beyond the notable achievements of its predecessor. These include the demonstration of temperatures that remain abiding, or flat, all the style from the hot core of the plasma to the normally cool outer edge. Sustaining the hot border expands the volume of plasma available for fusion and the product of flat temperature prevents instabilities that reduce plasma solitude from developing.

"The goals of the upgrade are to determine whether very low recycling lithium walls tin improve plasma confinement in a tokamak with neutral axle heating," said Dick Majeski, principal investigator for LTX-β. "If LTX-β is successful, we can movement on to experiments on liquid lithium in the National Spherical Torus Experiment-Upgrade [NSTX-U]," the flagship fusion experiment at PPPL.

Physicist Drew Elliot working on the LTX-β. (Elle Starkman/PPPL Function of Communications.)

Physicist Dick Majeski, principal investigator of the LTX-β. (Elle Starkman/PPPL Office of Communications.)