history of fusion research

A History of Fusion

Nearly a century of fusion energy progress.

Progress in fusion energy is nearing one century. In all that time, we achieved remarkable accomplishments, yet many more are to come. 

As the United States and the world accelerate toward fusion energy power plants, take a look at how we got here.

The 1920s–1970s

Arthur Eddington, a British astrophysicist, first published the theory that stars produce energy from the fusion of hydrogen to helium in 1926. A revolutionary idea, scientists worldwide soon rushed to confirm and advance our understanding of fusion energy.

In the 1950s, governments began declassifying fusion energy research in the name of peace. The International Atomic Energy Agency (IAEA) took charge of increasing global collaboration in 1958, encouraging all types of devices to be revealed, such as the now popular tokamak. International collaboration was sparked when President Carter and Prime Minister Fukuda signed a treaty on U.S.-Japan fusion research in 1978.

The United States hit its golden age of fusion in the 1970s, garnering broad governmental support and planning for future power plants.

The 1980s–2010s

Tough fiscal years beginning in the 1980s saw The United States scale back its fusion energy ambitions to focus on fusion science. This scientific approach is how the government primarily supports fusion today.

Meanwhile, in 1985, The United States and The Soviet Union made a historic agreement to put aside their rivalry and work together to make fusion energy a reality. They understood no one country could do it alone.

Today, that agreement manifests as ITER in southern France, where 35 countries work together to make fusion energy a reality.

The 2020s & Beyond

The global consensus that we need fusion energy has never been more substantial. Clean, reliable energy is a high priority. The fusion industry is springing up, technology is advancing, and ITER will soon be ready to go.

China and The United Kingdom are current hotspots for fusion dedication. While the United States invests in novel public-private partnerships to spur national industry, among other strategies, we need more support to accelerate the fusion timeline.

Approaches to Fusion

Four broad categories define how to produce fusion energy.

The Science of Fusion

Where the triple product reigns supreme.

Fusion in the United States

Three approaches distinguish the U.S. effort.

Why Fusion?

It could change everything.

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History of Fusion

Credit © iter organization, fusion history timeline, 1920-1930: understanding the stars and the atom.

Following Eddington’s paper, Robert d’Escourt Atkinson and Fritz Houtermans provided the first calculations of the rate of nuclear fusion in stars. And at the same time, Ernest Rutherford was exploring the structure of the atom. With his famous 1934 experiment, Rutherford showed the fusion of deuterium into helium, and observed that “an enormous effect was produced” during the process. His student Mark Oliphant used an updated version of the equipment, firing deuterium rather than hydrogen and discovered helium-3 and tritium , showing that heavy hydrogen nuclei could be made to react with each other. This was the first direct demonstration of fusion in the lab. This understanding of nuclear fusion was tied together by Hans Bethe’s work on stellar nucleosynthesis where he described that it is through proton -proton chain reactions that the Sun and stars release energy.

1950s: Enter the fusion machines

By the 1950s, researchers started looking at possibilities of replicating the process of nuclear fusion on Earth. And in 1950 soviet scientists Andrei Sakharov and Igor Tamm proposed the design for a type of magnetic confinement fusion device, the tokamak . This was followed, in 1951, by Lyman Spitzer’s concept for the stellarator . The stellarator concept dominated fusion research throughout the 1950s but lost its sway when the experimental research on tokamak systems by Soviet scientist Lev Artsimovich showed that the tokamak was a more efficient concept.

1970-1980: Designs on JET and beginnings for ITER

By the 1970s it was clear that attaining fusion energy would be one of science’s greatest challenges and collaboration might be key to meeting the challenge. European countries came together and began design work on the Joint European Torus , JET , in 1973. In 1977, the European commission gave the green signal for the project and Culham in Oxford, UK, was selected as the site for JET. The construction of JET, which would become the largest operational magnetic confinement plasma physics experiment, was completed on time and on budget in 1983 and the first plasmas were achieved.

The 80’s also saw the iron curtain being lifted slightly when ITER was set in motion at the Geneva Superpower Summit in November 1985. The idea of a collaborative international project to develop fusion energy for peaceful purposes was proposed by General Secretary Gorbachev of the former Soviet Union to US President Reagan.

1980-2000s: JET record

The first experiments using tritium was carried out in JET, making it the first reactor in the world to run on the fuel of a 50-50 mix of tritium and deuterium. In 1997, using this fuel, JET set a world record for fusion output at 16 MW from an input of 24 MW of heating. This is also the world record for Q , at 0.67. It should be stated that the world record was achieved in a very short instant of about 1 second. A Q of 1 is breakeven , and to achieve fusion energy the Q value must be greater than 1. The aim of ITER is to achieve a Q of 10.

JET sets world record

2000-present: A home for ITER

In 2005, the ITER Members unanimously agreed that ITER would be built in Cadarache in France. In December 2022, the ITER project passed the 77.7% milestone of work scope completed to first plasma. In 2015 the Wendelstein 7-X stellarator, which is a long-term back up strategy for the tokamak in the European Fusion Roadmap came into operation, and its first operational campaigns exceeded all expectations. In 2021 a new fusion energy world record of 59 MJ was achieved in JET in a 5 second long pulse, while burning only 170 micrograms of deuterium and tritium.

Nuclear fusion breakthrough: Decades of research are still needed before fusion can be used as clean energy

Assistant Professor, Mechanical and Aerospace Engineering, Carleton University

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Kristen Schell receives funding from NSERC, ECCC and the US Department of Energy.

Ahmed Abdulla receives funding from NSERC, ECCC and Carleton University

Carleton University provides funding as a member of The Conversation CA.

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The U.S. Department of Energy reported a major scientific breakthrough in nuclear fusion science in December 2022. For the first time, more energy was released from a fusion reaction than was used to ignite it.

While this achievement is indeed historic, it’s important to pause and reflect on the way ahead for fusion energy.

We are professors of sustainable and renewable energy engineering at Carleton University, where we research alternative energy technologies and systems that can move us to a low-carbon future.

We also teach our students how to navigate the treacherous terrain from lab-based findings to real-world applications.

Defining system boundaries

The efficiency of a potential fusion energy power plant remains to be seen. The reported fusion net gain actually required about 300 megajoules of energy input , which was not included in the energy gain calculation. This energy input, needed to power 192 lasers , came from the electric power grid.

In other words, the experiment used as much energy as the typical Canadian household does in two days. In doing so, the fusion reaction output enough energy to light just 14 incandescent bulbs for an hour.

The same is true of nuclear fission, which is the reaction inside current nuclear power plants. The complete fission of one kilogram of Uranium-235 — the fissile component of nuclear fuel — can generate about 77 terajoules . But we cannot convert all of that energy into useful forms like heat and electric power.

Instead, we have to engineer a complex system that can control the nuclear fission chain reaction and convert the generated energy into more useful forms.

This is what nuclear power plants do — they harness the heat generated during nuclear fission reactions to make steam. This steam drives a turbine connected to an electric power generator, which produces electricity. The overall efficiency of the cycle is less than 40 per cent.

In addition, not all of the uranium in the fuel is burned. Used fuel still contains about 96 per cent of its total uranium, and about a fifth of its fissile Uranium-235 content.

Increasing the amount of uranium spent in our current fleet is possible — it’s an ongoing sphere of work — but it poses enormous engineering challenges. The huge energy potential of nuclear fuel is currently mitigated by the engineering challenges of converting that energy into a useful form.

From science to engineering

Until recently, fusion has been seen primarily as a scientific experiment, not as an engineering challenge. This is rapidly changing and regulators are now investigating how deployment might unfold in the real world.

Regardless of the efficiency of a future fusion power plant, taking energy conversions from basic science to the real world will require overcoming a multitude of challenges.

Because fission faced many of the same challenges as fusion now does, we can learn a lot from its history. Fission also had to move from science to engineering before the commercial industry could take off.

The science of fusion energy, as with nuclear fission, is rooted in efforts to develop nuclear weapons. Notably, several nuclear physicists who helped develop the nuclear bomb wanted to “ prove that this discovery was not just a weapon .”

The early history of nuclear power was one of optimism — of declarations the technology would advance and be able to meet our need for ever-increasing amounts of energy. Eventually, fusion power would come along and electricity would become “too cheap to meter.”

Lessons learned

What have we learned over the past 70 years since the onset of nuclear power? First, we’ve learned about the potentially devastating risk of technology lock-in , which occurs when an industry becomes dependent on a specific product or system.

Today’s light-water fission reactors — reactors that use normal water as opposed to water enriched with a hydrogen isotope — are an example of this. They were not chosen because they were the most desirable, but for other reasons.

These factors include government subsidies that favoured these designs; the U.S. Navy’s interest in developing smaller-scale pressurized water reactors for submarines and surface warships; advances in uranium enrichment technology as a result of the U.S. nuclear weapons program; uncertainties regarding nuclear costs that led to the assumption that large light-water reactors are simply scaled-up versions of smaller ones; and conservatism regarding design choices given the high costs and risks associated with nuclear power development.

We have been struggling to move to other technologies ever since.

Second, we’ve learned that size matters. Large reactors cost more to build per unit of capacity than smaller units. In other words, engineers misunderstood the concept of economies of scale and doomed their industry in the process.

Large infrastructure projects are extremely complex systems that rely on enormous work forces and co-ordination. They can be managed, but they usually go over-budget and fall behind schedule. Modular technologies exhibit better affordability , cost control and economies, but micro and small nuclear reactors will also be economically challenged.

Third, regulatory regimes must be developed for fusion. If the industry coalesces too quickly around a first-generation design, the consequences for the regulation of future reactors could be severe.

Fourth, choosing locations for new power plants and societal acceptance are key. Fusion has an advantage because its technology is more of a blank slate than fission when it comes to public opinion. The positive associations the public has with fusion must be maintained by prudent design decisions and adopting best practices for community engagement .

The same is true of how the industry will choose to handle the waste challenge. Fusion reactors generate large amounts of waste, though not the same kind fission does .

A call to action

Our research on nuclear energy innovation reveals that challenges facing nuclear fusion can be overcome, but they require prudent leadership, decades of research, significant amounts of funding and focus on technology development.

Billions of dollars are needed to advance nuclear fission technology, and we have far more experience with fission than with fusion. An appetite for funding must be demonstrated by governments, electric utility companies and entrepreneurs.

Fusion’s promise is vast and there is exciting work being done to advance it outside of this recent breakthrough, including by private companies . Decades of research and development are needed before fusion can meaningfully contribute to our energy system.

Our central message is a call to action: fusion engineers, researchers, industry and government must organize to investigate and mitigate the challenges that face fusion, including in the design of the first generation of power plants.

There is no substitute to deep and rapid decarbonization of the energy system if we want to save our planet from climate catastrophe. We are proud to be training the next generation of energy engineers to design new and better energy solutions.

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A Brief History of U.S. Funding of Fusion Energy

Rachel margraf march 27, 2021, submitted as coursework for ph241 , stanford university, winter 2021, introduction.

Despite decades of research and government support, fusion energy remains a technology of the future - with tremendous potential but still far from commercial viability. Fusion energy reactors, which generate electricity from the heat produced from the fusion of the nuclei of light atoms, like hydrogen, have many advantages over conventional energy technologies. Fusion reactors do not produce harmful carbon dioxide as fossil fuel plants do, they produce far less nuclear waste than nuclear fission reactors, and unlike wind and solar sources, they can be run 24 hours a day. However, there are many technical challenges associated with fusion energy, primarily because fusion reactions must occur within a hot plasma in order to generate energy. This condition necessities extensive basic research to understand how to confine plasma within a reactor and develop materials which can withstand sustained plasma exposure. [1] Such research often requires large-scale experiments which require government funding to progress. Thus, many attribute the slow progress of fusion energy development in the United States to insufficient federal funding. This article will give a broad overview of the history of fusion funding in the United States.

Fusion Funding History

The United States' magnetic fusion energy program started within the Atomic Energy Commission (AEC) around 1951, and was declassified in 1957. [1] This declassification enabled international scientific collaborations and discussions of fusion research. The 1950s and 1960s saw the early development of several plasma confinement concepts including the tokamak, stellarator, pinch and mirror methods. [2] The tokamak design was considered especially promising, and a fossil fuel energy crisis in the 1970s provided the political will to invest in large-scale tokamak studies, including the Tokamak Fusion Test Reactor (TFTR). Fusion energy, overseen by the Energy Research and Development Administration (ERDA) from 1976- 1978, accordingly saw a large increase in funding in the mid 1970s and early 1980s. [1]

As the energy crisis subsided, however, funding in fusion energy fell again in the mid-1980s. The fusion energy sciences program, now being overseen by the Department of Energy (DOE), found difficulty acquiring funding for new large tokamak projects. The successor to TFTR, the Compact Ignition Torus (CIT) underwent significant planning in the late 1980s, but was canceled by Congress in the early 1990s. [1] Faced with the increasing costs of building the larger experimental facilities that would be needed to demonstrate fusion energy, the conversation in Congress began to shift towards international cooperations where the cost of new tokamak facilities could be shared by several countries.

The concept for the International Thermonuclear Experimental Reactor (ITER) appeared in the late 1980s. This collaboration, between the European Union, China, India, Japan, Korea, Russia and the United States, planned for the construction of a large "demo" reactor in France in which the costs would be shared by the collaborating countries. While Congress decided that ITER would be a more cost-effective option for advancing tokamak technology than new domestic tokamaks, Congress has wavered at times in its funding commitment to ITER. From 1988-1999, Congress provided funds for planning on the ITER project. Congress pulled the United States out of ITER in 1999, before later rejoining in 2004. [3,7] Congress directed the DOE to cut United States contributions to ITER again in 2008, although DOE documents suggest the DOE still managed to provide a small portion of the promised funds to ITER that year, demonstrating the DOE's committment to the project. [11,25] The United States has committed to covering 9.1% of ITER's construction costs, and 13% of ITER's operations costs once it begins operation. [22] Most of the construction costs are "in-kind" contributions, in which the United States provides materials and equipment to the construction. This arrangement enables some components of ITER to still be developed and built in the United States before being delivered to ITER, maintaining some tokamak fusion research in the United States related to ITER.

Domestically, the United States continues smaller-scale fusion research projects. In 1995, Congress directed the DOE to restructure itself primarily as a science program rather than as an energy program. [3] Research on tokamaks and other reactor concepts, including stellerators, continued, but without new large scale facilities. Research in plasma science and materials development became larger research focuses in order to work within the domestic fusion budget, which has been essentially flat since 1995. [22]

The United States had a period of strong funding for fusion energy in the mid 1970s to mid 1980s, but has since deferred the construction of large tokamak fusion reactor facilities to international collaborations. The 1970s to 1980s period, when the United States saw urgency in advancing new energy technologies, promoted rapid domestic research into tokamak reactors. However, this urgency was not sustained over a long enough term for tokamak reactors to come to fruition as a commercially viable technology. The United States has continued to invest considerable funding and resources into fusion energy over its 60-70 year history, but perhaps not at high enough levels to suggest that fusion energy is an urgent priority for the United States. While ITER and other projects may eventually make commercially viable fusion a reality, it is hard not to wonder if fusion energy would be much further along today had the political will been there thirty years ago to make it so.

© Rachel Margraf. The author warrants that the work is the author's own and that Stanford University provided no input other than typesetting and referencing guidelines. The author grants permission to copy, distribute and display this work in unaltered form, with attribution to the author, for noncommercial purposes only. All other rights, including commercial rights, are reserved to the author.

[1] U. Schumacher, "Status and Problems of Fusion Reactor Development," Naturwiss. 88 , 102 (2001).

[2] L. A. El-Guebaly, "Fifty Years of Magnetic Fusion Research (1958-2008): Brief Historical Overview and Discussion of Future Trends," Energies 3 , 1067 (2010).

[3] R. E. Rowberg, "Congress and the Fusion Energy Sciences Program: A Historical Analysis," Congressional Research Service, RL30417 , January 2000.

[4] C. Behrens, "Appropriations for FY2002: Energy and Water Development," Congressional Research Service, RL31007 , February 2002, p. 9.

[5] C. Behrens, "Appropriations for FY2003: Energy and Water Development," Congressional Research Service, RL31307 , February 2003, p. 14.

[6] "FY 2005 Congressional Budget Request: Science, Nuclear Waste Disposal, Defense Nuclear Waste Disposal, Departmental Administration, Inspector General, Working Capital Fund," U.S. Department of Energy, DOE/ME-0035, Volume 4 , February 2004, p. 11.

[7] "FY 2006 Congressional Budget Request: Science, Nuclear Waste Disposal, Defense Nuclear Waste Disposal, Departmental Administration, Inspector General, Working Capital Fund," DOE/ME-0049, Volume 4 , February 2005, pp. 11, 388.

[8] "FY 2007 Congressional Budget Request: Science, Nuclear Waste Disposal, Defense Nuclear Waste Disposal, Departmental Administration, Inspectcor General, Working Capital Fund," U.S. Department of Energy, DOE/CF-005, Volume 4 , February 2008, pp. 11, 468.

[9] "FY 2008 Congressional Budget Request: Science, Nuclear Waste Disposal, Defense Nuclear Waste Disposal, Departmental Administration, Inspector General, Loan Guarantee Program, Working Capital Fund," U.S. Department of Energy, DOE/CF-017, Volume 4 , February 2007, pp. 13, 407.

[10] "FY 2009 Congressional Budget Request: Science," U.S. Department of Energy, DOE/CF-027, Volume 4 , February 2008, pp. 7, 394.

[11] "FY 2010 Congressional Budget Request: Science," U.S. Department of Energy, DOE/CF-038, Volume 4 , May 2009, pp. 7, 351.

[12] "FY 2011 Congressional Budget Request: Science," U.S. Department of Energy, DOE/CF-0050, Volume 4 , February 2010, pp. 7, 244.

[13] "FY 2012 Congressional Budget Request: Science," U.S. Department of Energy, DOE/CF-0060, Volume 4 , February 2011, pp. 7, 243.

[14] "FY 2013 Congressional Budget Request: Science, Advanced Research Projects Agency - Energy," U.S. Department of Energy, DOE/CF-0074, Volume 4 , February 2012, pp. 11, 185.

[15] "FY 2014 Congressional Budget Request: Science, Advanced Resedarch Projects Agency - Energy (ARPA-E)," U.S. Department of Energy, DOE/CF-0087, Volume 4 , April 2013, pp. 3, 165.

[16] "FY 2015 Congressional Budget Request: Science, Advanced Research Projects Agency - Energy," U.S. Department of Energy, DOE/CF-0099, Volume 4 , March 2014, p 118.

[17] "FY 2016 Congressional Budget Request: Science, Advanced Reseaerch Projects Agency - Energy," U.S. Department of Energy, DOE/CF-0110, Volume 4 , February 2015, p. 13.

[18] "FY 2017 Congressional Budget Request: Science, Advanced Research Projects Agency - Energy," U.S. Department of Energy, DOE/CF-0122, Volume 4 , February 2016, p. 15.

[19] "FY 2018 Congressional Budget Request: Science," U.S. Department of Energy, DOE/CF-0131, Volume 4 , May 2017, p. 13.

[20] "FY 2019 Congressional Budget Request: Science," U.S. Department of Energy, DOE/CF-0142, Volume 4 , March 2018, p. 13.

[21] "FY 2020 Congressional Budget Request: Science," U.S. Department of Energy, DOE/CF-0154, Volume 4 , March 2019, p. 13.

[22] "FY 2021 Congressional Budget Request: Science," U.S. Department of Energy, DOE/CF-0165, Volume 4 , February 2020, p. 15.

[23] " Statistical Abstract of the United States: 2012 ," United States Census Bureau, August 2011, Table 724, p. 473.

[24] "Consumer Price Index - December 2020," U.S. Bureau of Labor Statistics, USDL-21-0024 ," January 2021, Table 5.

[25] "Federal Research and Development Funding: FY2008," Congressional Research Service, RL34048 , February 2008, p. 4.

For First Time, Researchers Produce More Energy from Fusion Than Was Used to Drive It, Promising Further Discovery in Clean Power  and Nuclear Weapons Stewardship

WASHINGTON, D.C. — The U.S. Department of Energy (DOE) and DOE’s National Nuclear Security Administration (NNSA) today announced the achievement of fusion ignition at Lawrence Livermore National Laboratory (LLNL)—a major scientific breakthrough decades in the making that will pave the way for advancements in national defense and the future of clean power. On December 5, a team at LLNL’s National Ignition Facility (NIF) conducted the first controlled fusion experiment in history to reach this milestone, also known as scientific energy breakeven, meaning it produced more energy from fusion than the laser energy used to drive it. This historic, first-of-its kind achievement will provide unprecedented capability to support NNSA’s Stockpile Stewardship Program and will provide invaluable insights into the prospects of clean fusion energy, which would be a game-changer for efforts to achieve President Biden’s goal of a net-zero carbon economy.

“This is a landmark achievement for the researchers and staff at the National Ignition Facility who have dedicated their careers to seeing fusion ignition become a reality, and this milestone will undoubtedly spark even more discovery,” said U.S. Secretary of Energy Jennifer M. Granholm . “The Biden-Harris Administration is committed to supporting our world-class scientists—like the team at NIF—whose work will help us solve humanity’s most complex and pressing problems, like providing clean power to combat climate change and maintaining a nuclear deterrent without nuclear testing.”

“We have had a theoretical understanding of fusion for over a century, but the journey from knowing to doing can be long and arduous. Today’s milestone shows what we can do with perseverance,” said Dr. Arati Prabhakar, the President’s Chief Advisor for Science and Technology and Director of the White House Office of Science and Technology Policy .

“Monday, December 5, 2022, was a historic day in science thanks to the incredible people at Livermore Lab and the National Ignition Facility. In making this breakthrough, they have opened a new chapter in NNSA’s Stockpile Stewardship Program,” said NNSA Administrator Jill Hruby . “I would like to thank the members of Congress who have supported the National Ignition Facility because their belief in the promise of visionary science has been critical for our mission. Our team from around the DOE national laboratories and our international partners have shown us the power of collaboration.”

“The pursuit of fusion ignition in the laboratory is one of the most significant scientific challenges ever tackled by humanity, and achieving it is a triumph of science, engineering, and most of all, people,” LLNL Director Dr. Kim Budil said. “Crossing this threshold is the vision that has driven 60 years of dedicated pursuit—a continual process of learning, building, expanding knowledge and capability, and then finding ways to overcome the new challenges that emerged. These are the problems that the U.S. national laboratories were created to solve.”

“This astonishing scientific advance puts us on the precipice of a future no longer reliant on fossil fuels but instead powered by new clean fusion energy,” U.S. Senate Majority Leader Charles Schumer said. I commend Lawrence Livermore National Labs and its partners in our nation’s Inertial Confinement Fusion (ICF) program, including the University of Rochester’s Lab for Laser Energetics in New York, for achieving this breakthrough. Making this future clean energy world a reality will require our physicists, innovative workers, and brightest minds at our DOE-funded institutions, including the Rochester Laser Lab, to double down on their cutting-edge work. That’s why I’m also proud to announce today that I’ve helped to secure the highest ever authorization of over $624 million this year in the National Defense Authorization Act for the ICF program to build on this amazing breakthrough.”

“After more than a decade of scientific and technical innovation, I congratulate the team at Lawrence Livermore National Laboratory and the National Ignition Facility for their historic accomplishment,” said U.S. Senator Dianne Feinstein (CA) . “This is an exciting step in fusion and everyone at Lawrence Livermore and NIF should be proud of this milestone achievement.”

“This is an historic, innovative achievement that builds on the contributions of generations of Livermore scientists. Today, our nation stands on their collective shoulders. We still have a long way to go, but this is a critical step and I commend the U.S. Department of Energy and all who contributed toward this promising breakthrough, which could help fuel a brighter clean energy future for the United States and humanity,” said U.S. Senator Jack Reed (RI) , the Chairman of the Senate Armed Services Committee.

“This monumental scientific breakthrough is a milestone for the future of clean energy,” said U.S. Senator Alex Padilla (CA) . “While there is more work ahead to harness the potential of fusion energy, I am proud that California scientists continue to lead the way in developing clean energy technologies. I congratulate the scientists at Lawrence Livermore National Laboratory for their dedication to a clean energy future, and I am committed to ensuring they have all of the tools and funding they need to continue this important work.”

“This is a very big deal. We can celebrate another performance record by the National Ignition Facility. This latest achievement is particularly remarkable because NIF used a less spherically symmetrical target than in the August 2021 experiment,” said U.S. Representative Zoe Lofgren (CA-19) . “This significant advancement showcases the future possibilities for the commercialization of fusion energy. Congress and the Administration need to fully fund and properly implement the fusion research provisions in the recent CHIPS and Science Act and likely more. During World War II, we crafted the Manhattan Project for a timely result. The challenges facing the world today are even greater than at that time. We must double down and accelerate the research to explore new pathways for the clean, limitless energy that fusion promises.”

“I am thrilled that NIF—the United States’ most cutting-edge nuclear research facility—has achieved fusion ignition, potentially providing for a new clean and sustainable energy source in the future. This breakthrough will ensure the safety and reliability of our nuclear stockpile, open new frontiers in science, and enable progress toward new ways to power our homes and offices in future decades,” said U.S. Representative Eric Swalwell (CA-15) . “I commend the scientists and researchers for their hard work and dedication that led to this monumental scientific achievement, and I will continue to push for robust funding for NIF to support advancements in fusion research.”

LLNL’s experiment surpassed the fusion threshold by delivering 2.05 megajoules (MJ) of energy to the target, resulting in 3.15 MJ of fusion energy output, demonstrating for the first time a most fundamental science basis for inertial fusion energy (IFE). Many advanced science and technology developments are still needed to achieve simple, affordable IFE to power homes and businesses, and DOE is currently restarting a broad-based, coordinated IFE program in the United States. Combined with private-sector investment, there is a lot of momentum to drive rapid progress toward fusion commercialization.

Fusion is the process by which two light nuclei combine to form a single heavier nucleus, releasing a large amount of energy. In the 1960s, a group of pioneering scientists at LLNL hypothesized that lasers could be used to induce fusion in a laboratory setting. Led by physicist John Nuckolls, who later served as LLNL director from 1988 to 1994, this revolutionary idea became inertial confinement fusion, kicking off more than 60 years of research and development in lasers, optics, diagnostics, target fabrication, computer modeling and simulation, and experimental design.

To pursue this concept, LLNL built a series of increasingly powerful laser systems, leading to the creation of NIF, the world’s largest and most energetic laser system. NIF—located at LLNL in Livermore, Calif.—is the size of a sports stadium and uses powerful laser beams to create temperatures and pressures like those in the cores of stars and giant planets, and inside exploding nuclear weapons.

Achieving ignition was made possible by dedication from LLNL employees as well as countless collaborators at DOE’s Los Alamos National Laboratory, Sandia National Laboratories, and Nevada National Security Site; General Atomics; academic institutions, including the University of Rochester’s Laboratory for Laser Energetics, the Massachusetts Institute of Technology, the University of California, Berkeley, and Princeton University; international partners, including the United Kingdom’s Atomic Weapons Establishment and the French Alternative Energies and Atomic Energy Commission; and stakeholders at DOE and NNSA and in Congress.

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• Published: 14 December 2022

Highlights of 2022

A milestone in fusion research is reached

• R. Betti 1  

Nature Reviews Physics volume  5 ,  pages 6–8 ( 2023 ) Cite this article

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• Laser-produced plasmas
• Nuclear fusion and fission

Ignition of a millimetre-sized pellet containing a mix of deuterium–tritium, published in 2022, puts to rest questions about the capability of lasers to ignite thermonuclear fuel.

Key advances

An experiment at the National Ignition Facility, published in 2022, achieved ignition for the first time via inertial confinement fusion.

This achievement comes on the back of other experiments in 2020–2021, which achieved the first demonstration of a burning plasma in the laboratory.

These advances arise from a long series of improvements to the experimental design, and in turn suggest pathways to further increase the fusion yield.

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Abu-Shawareb, H. et al (Indirect Drive ICF collaboration). Lawson criterion for ignition exceeded in an inertial fusion experiment. Phys. Rev. Lett. 129 , 075001 (2022).

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Le Pape, S. et al. Fusion energy output greater than the kinetic energy of an imploding shell at the National Ignition Facility. Phys. Rev. Lett. 120 , 245003 (2018).

Zylstra, A. B. et al. Burning plasma achieved in inertial fusion. Nature 601 , 542–548 (2022).

Kritcher, A. L. et al. Design of an inertial fusion experiment exceeding the Lawson criterion for ignition. Phys. Rev. E 106 , 025201 (2022).

Zylstra, A. B. et al. Experimental achievement and signatures of ignition at the National Ignition Facility. Phys. Rev. E 106 , 025202 (2022).

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Acknowledgements

The author thanks O. Hurricane, A. Kritcher, A. Zylstra, C. Deeney and E. M. Campbell for thoughtful comments. This material is based upon work supported by the US Department of Energy National Nuclear Security Administration under award nos. DE-NA0003856 and DE-NA0003868, the University of Rochester, and the New York State Energy Research and Development Authority.

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Laboratory for Laser Energetics and Departments of Mechanical Engineering and Physics & Astronomy, University of Rochester, Rochester, NY, USA

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Betti, R. A milestone in fusion research is reached. Nat Rev Phys 5 , 6–8 (2023). https://doi.org/10.1038/s42254-022-00547-y

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Published : 14 December 2022

Issue Date : January 2023

DOI : https://doi.org/10.1038/s42254-022-00547-y

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A history of fusion research and development Part 5

This article is the last one in a 5 part series on the history of fusion research and development by Matteo Barbarino, a Nuclear Plasma Fusion Specialist from the International Atomic Energy Agency (IAEA)

The 28th Fusion Energy Conference (FEC 2020) will take place in Nice, France, this year in October. Meanwhile, let’s glance through some of the core papers from the FEC 2018 and learn about how they relate to historic developments in fusion energy research.

Overview of HL-2A Recent Experiments (OV/5-1)

The HL-2A tokamak at the Southwestern Institute of Physics (SWIP), in China, is a great example of how fusion research institutes work together worldwide and support one another. Since 2002, this tokamak operates using some parts from the old German tokamak ASDEX .

In addition, scientists and engineers at SWIP are currently working on an upgrade of the machine, HL-2M, which will come online this year. When operational, HL-2M will contribute to filling the gap in the understanding of magnetic confinement plasma physics for the operation of future fusion power reactors.

This paper highlighted the significant progress achieved on the HL-2A in reaching high performance operation and plasma instabilities control.

First plasma in HL-2A was obtained at the end of 2002, and first results from the experiments were presented at the FEC 2004:

LIU, Y., et al., “Recent advances in the HL-2A tokamak experiments”, Fusion Energy Conference (Proc. 20th Int. Conf. Vilamoura, 2004, Paper No. OV/5-1Ra) IAEA, Vienna (2005).

Physics Research on the TCV Tokamak Facility: from Conventional to Alternative Scenarios and beyond (OV/5-2)

An all-round device with highly flexible heating systems, extended diagnostics and the capability of producing a variety of plasma shapes, the TCV tokamak at the Swiss Plasma Center is not only employed in a large number of research areas in support of ITER, but also in exploring advanced tokamak scenarios and divertor configurations with an eye to DEMO . Studying alternative shapes can help improve plasma confinement and stability.

T his paper highlighted recent progress and results from disruption avoidance and mitigation, and first successful generation of a doublet (figure of eight) plasma configuration, among others.

First experimental results from TCV and its plasma shaping versatility were presented at the FEC 1994:

LISTER, J.B., et al., “Variable configuration plasmas in TCV”, Plasma Physics and Controlled Nuclear Fusion Research (Proc. 15th Int. Conf. Seville, 1994, Paper No. CN-60/A5-2) IAEA, Vienna (1995) 627.

Overview of Operation and Experiments in the ADITYA-U Tokamak (OV/5-3)

ADITYA is the first tokamak fully designed and built in India. This medium-size tokamak contributes to the international database of experimental results in disruption mitigation and it was recently equipped with a new divertor.

This paper highlighted the results achieved operating the upgraded device.

ADITYA first results were presented at the FEC 1992:

JHA, R., et al., “Intermittency in tokamak edge turbulence”, Plasma Physics and Controlled Nuclear Fusion Research (Proc. 14th Int. Conf. Würzburg, 1992, Paper No. CN-56/A-7-9) IAEA, Vienna (1993) 467.

Tokamak Research in Ioffe Institute (OV/5-4)

Founded in 1918, the Ioffe Institute , in Russia, recently celebrated its 100th anniversary and more than six decades of remarkable contributions to plasma physics and fusion research.

This paper presented recent tokamak research on GLOBUS-M and TUMAN-3M.

The first small tokamak at Ioffe Institute, TUMAN-1, was put into operation in 1964:

GOLANT, V.E., et al., “Plasma compression by a magnetic field in a toroidal-type device”, Plasma Physics and Controlled Nuclear Fusion Research (Proc. 2nd Int. Conf. Culham, 1965) IAEA, Vienna (1966) 829.

NSTX-U Theory, Modelling and Analysis Results (OV/5-5Ra) and Overview of New MAST Physics in Anticipation of First Results from MAST Upgrade (OV/5-5Rb)

NSTX at the Princeton Plasma Physics Laboratory , in the United States, and MAST at Culham Centre for Fusion Energy (CCFE), in the United Kingdom, are two fusion devices operating since the late 1990s based on the spherical tokamak concept – an apple-shaped machine configuration that holds the plasma in tighter magnetic fields, forming a more compact core.

Scientists and engineers at the Oak Ridge National Laboratory (ORNL), in the United States, and at CCFE were pioneers of this concept which features a high plasma beta (the ratio of plasma to magnetic pressure) and a very large bootstrap current which are key requirements for steady-state operation. These attributes may offer the possibility of a having more compact device for the same total fusion power but increase the demand on the materials technology.

While MAST is undergoing an upgrade which is nearing completion, NSTX-U (U=Upgrade) operated for some weeks in 2016 but it has been undergoing repair since then. When back online, both machines will provide new capabilities to address key physics and technologies issues for the operation of ITER and also for the performance of future spherical tokamaks .

These papers highlighted the results from NSTX-U studies and the analysis of MAST data and numerical modelling which contribute to predicting the performance of future spherical tokamaks.

The idea of a spherical tokamak concept raised from magnetohydrodynamics (MHD) stability calculations indicating that a low-aspect-ratio tokamak would allow very high plasma beta. News of a proposal for a Spherical Torus Experiment (STX) was announced at the FEC 1986:

CARRERAS, B.A., et al., “MHD stability in low aspect ratio tokamaks”, Plasma Physics and Controlled Nuclear Fusion Research (Proc. 11th Int. Conf. Kyoto, 1986, Vol. 2, Paper No. CN-47/E-I-2-4) IAEA, Vienna (1987) 53.

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Research finds Americans supportive but misinformed about fusion energy's promise

by University of Oklahoma

Research led by Hank Jenkins-Smith, Ph.D., director of the Institute for Public Policy Research and Analysis at the University of Oklahoma, explores American adults' perceptions of fusion energy. This first-of-its-kind study reveals broad public support from respondents, but their limited knowledge of the technology and frequent misconceptions could pose a challenge to those seeking to develop fusion energy in the U.S.

The paper is published in the journal Fusion Science and Technology .

"Our research questions public perceptions of nuclear fission and whether these opinions could affect the potential for fusion energy to become a major power source for the U.S. electrical grid," he said. "It turns out that these social perspectives are significant and must be addressed by engineers, physicists, and regulatory specialists for this technology to be widely adopted."

Fission energy, or the splitting of atoms, differs from fusion energy, which combines two atoms under extreme heat and pressure. According to the International Atomic Energy Agency, the fusion process is intrinsically safe. It offers an abundant source of energy with very little greenhouse gas emissions or long-living radioactive waste. The same cannot be said for fission energy.

"We discovered that less than half of all respondents had heard of fusion energy, and many confused fission and fusion," he said. "This confusion, along with pop cultural references of Godzilla or Homer Simpson and memories of spectacular accidents, like those at Three Mile Island, Chernobyl or Fukushima, cause them to believe that fusion technology is extraordinarily risky."

Based on their research findings, Jenkins-Smith's team determined that the public wants decision-makers to think carefully about the safety constraints and future incentives for fusion energy in America.

"The fusion industry should look at how the fission industry has developed an amazing safety culture. They've built in many layers and processes to reduce the possibility of accidents," he said. "These are things that fusion regulators must develop ahead of time rather than waiting for a disaster to strike and fixing the problem later."

According to Jenkins-Smith, messaging is an important takeaway from this research. He believes there are potential opportunities for misleading statements, leveraged by fusion opponents, to confuse and scare Americans and to undermine public trust for information from technology supporters.

"Because the public is not well-informed, opponents could fairly easily generate false narratives linking fission to fusion and thereby poisoning public acceptance of fusion moving forward," he said.

"To combat this, developers, regulators, and advocacy groups must be aware of and careful about what they say about fusion energy. They must have humility and avoid making overly optimistic claims that will be difficult or impossible to achieve. Doing so will go a long way in retaining societal acceptance of this technology ."

Study respondents currently express high trust for regulators and operators of prospective fusion energy facilities. These positive views of fusion are based, in part, on technological optimism.

"Americans have a propensity to believe that new technologies can help improve their lives. We're technological optimists," he said. "The more technologically optimistic someone is, the more likely they are to support fusion energy . Harnessing this optimism could help grow our economy, tackle climate change, and address international security and energy concerns."

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• The Inventory

New Kind of Fusion Reactor Built at Government Lab

The stellarator has permanent magnets, a first for a fusion experiment..

A team of physicists and engineers at Princeton Plasma Physics Laboratory built a twisting fusion reactor known as a stellarator that uses permanent magnets, showcasing a potentially cost-effective way of building the powerful machines. Their experiment, called MUSE, relies on 3D-printed and off-the-shelf parts.

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Nuclear fusion, the reaction that powers stars like our Sun, produces huge amounts of energy by merging atoms (not to be confused with nuclear fission, which produces less energy by splitting atoms). Nuclear fission is the reaction at the core of modern nuclear reactors that power electric grids; scientists have yet to crack the code on nuclear fusion as an energy source. Even once that long-sought goal is reached, scaling the technology and making it commercially viable is its own beast .

Stellarators are cruller-shaped devices that contain high-temperature plasmas, which can bed tuned to foster the conditions for fusion reactions. They are similar to tokamaks, doughnut-shaped devices that run fusion reactions . Tokamaks rely on solenoids , which are magnets that carry electric current. MUSE is different.

“Using permanent magnets is a completely new way to design stellarators,” said Tony Qian, a graduate student at Princeton Plasma Physics Laboratory and lead author of two papers published in the Journal of Plasma Physics and Nuclear Fusion that describe the design of the MUSE experiment. “This technique allows us to test new plasma confinement ideas quickly and build new devices easily.”

Permanent magnets don’t need electric current to generate their magnet fields and can be purchased off-the-shelf. The MUSE experiment stuck such magnets onto a 3-D printed shell.

“I realized that even if they were situated alongside other magnets, rare-earth permanent magnets could generate and maintain the magnetic fields necessary to confine the plasma so fusion reactions can occur,” Michael Zarnstorff, a research scientist at the laboratory and principal investigator of the MUSE project, in a press release. “That’s the property that makes this technique work.”

Last year, scientists at the Department of Energy’s Lawrence Livermore National Laboratory (LLNL) achieved breakeven in a fusion reaction ; that is, the reaction produced more energy than it took to power it . However, that accolade neglects to account for the “wall power” necessary to induce the reaction. In other words, there’s still a long, long road ahead.

The LLNL breakthrough was done by shining powerful lasers at a pellet of atoms, a different process than the plasma-based fusion reactions that occur in tokamaks and stellarators. Little tweaks to the devices, like the implementation of permanent magnets in MUSE or an upgraded tungsten diverter in the KSTAR tokamak , make it easier for scientists to replicate the experimental setups and perform experiments at high temperatures for longer.

Taken together, these innovations will allow scientists to do more with the plasmas at their fingertips, and maybe—just maybe—reach the vaunted goal of usable and scalable fusion energy.

Correction: A previous version of this article incorrectly referred to Princeton Plasma Physics Laboratory as part of Princeton University. Though the university manages the lab for the Department of Energy, the lab is not part of the university.

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Electrical Engineering and Systems Science > Image and Video Processing

Title: lidar-guided cross-attention fusion for hyperspectral band selection and image classification.

Abstract: The fusion of hyperspectral and LiDAR data has been an active research topic. Existing fusion methods have ignored the high-dimensionality and redundancy challenges in hyperspectral images, despite that band selection methods have been intensively studied for hyperspectral image (HSI) processing. This paper addresses this significant gap by introducing a cross-attention mechanism from the transformer architecture for the selection of HSI bands guided by LiDAR data. LiDAR provides high-resolution vertical structural information, which can be useful in distinguishing different types of land cover that may have similar spectral signatures but different structural profiles. In our approach, the LiDAR data are used as the "query" to search and identify the "key" from the HSI to choose the most pertinent bands for LiDAR. This method ensures that the selected HSI bands drastically reduce redundancy and computational requirements while working optimally with the LiDAR data. Extensive experiments have been undertaken on three paired HSI and LiDAR data sets: Houston 2013, Trento and MUUFL. The results highlight the superiority of the cross-attention mechanism, underlining the enhanced classification accuracy of the identified HSI bands when fused with the LiDAR features. The results also show that the use of fewer bands combined with LiDAR surpasses the performance of state-of-the-art fusion models.

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