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Here’s how scientists reached nuclear fusion ‘ignition’ for the first time.

The experiment, performed in 2022, also revealed a never-before-seen phenomenon

In December 2022, scientists at the National Ignition Facility (pictured) achieved nuclear fusion “ignition,” in which the energy produced by the fusing of atomic nuclei exceeds that needed to kick the fusion off.

Jason Laurea/LLNL

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By Emily Conover

February 16, 2024 at 9:30 am

One of nuclear fusion’s biggest advances wouldn’t have happened without some impeccable scientific artistry.

In December 2022, researchers at Lawrence Livermore National Laboratory in California created fusion reactions that produced an excess of energy — a first. In the experiment, 192 lasers blasted a small chamber, setting off fusion reactions — in which smaller atomic nuclei merge to form larger ones — that released more energy than initially kicked them off ( SN: 12/12/22 ). It’s a milestone known as “ignition,” and it has been decades in the making.

Now, researchers have released details of that experiment in five peer-reviewed papers published online February 5 in Physical Review Letters and Physical Review E . The feat demanded an extraordinary level of finesse, tweaking conditions just so to get more energy out of the lasers and create the ideal conditions for fusion.

The work is “exquisitely beautiful,” says physicist Peter Norreys of the University of Oxford. Norreys, who was not involved with the research, compares the achievement to conducting a world-class orchestra: Different elements of the experiment had to be meticulously coordinated and precisely timed.

Scientists also discovered a long-predicted heating effect that could expose the physics of other violent environments, such as exploding stars called supernovas. “People say [physics is] a dry subject,” Norreys says. “But I always think that physics is at the very forefront of creativity,”

The road to nuclear fusion’s big break

Fusion, the same process that takes place in the sun, is an appealing energy source. Fusion power plants wouldn’t emit greenhouse gases. And unlike current nuclear fission power plants, which split atomic nuclei to produce energy, nuclear fusion plants wouldn’t produce dangerous, long-lived radioactive waste. Ignition is the first step toward harnessing such power.

Generating fusion requires extreme pressures and temperatures. In the experiment, the lasers at LLNL’s National Ignition Facility pelted the inside of a hollow cylinder, called a hohlraum, which is about the size of a pencil eraser. The blast heated the hohlraum to a sizzling 3 million degrees Celsius — so hot that it emitted X-rays. Inside this X-ray oven, a diamond capsule contained the fuel: two heavy varieties of hydrogen called deuterium and tritium. The radiation vaporized the capsule’s diamond shell, triggering the fuel to implode at speeds of around 400 kilometers per second, forming the hot, dense conditions that spark fusion.

Previous experiments had gotten tantalizingly close to ignition ( SN: 8/18/21 ). To push further, the researchers increased the energy of the laser pulse from 1.92 million joules to 2.05 million joules. This they accomplished by slightly lengthening the laser pulse, which blasts the target for just a few nanoseconds, extending it by a mere fraction of a nanosecond. (Increasing the laser power directly, rather than lengthening the pulse, risked damage to the facility.)

The team also thickened the capsule’s diamond shell by about 7 percent — a difference of just a few micrometers — which slowed down the capsule’s implosion, allowing the scientists to fully capitalize on the longer laser pulse.  “That was a quite remarkable achievement,” Norreys says.

But these tweaks altered the symmetry of the implosion, which meant other adjustments were needed. It’s like trying to squeeze a basketball down to the size of a pea, says physicist Annie Kritcher of LLNL, “and we’re trying to do that spherically symmetric to within 1 percent.”

That’s particularly challenging because of the mishmash of electrically charged particles, or plasma, that fills the hohlraum during the laser blast. This plasma can absorb the laser beams before they reach the walls of the hohlraum, messing with the implosion’s symmetry.

To even things out, Kritcher and colleagues slightly altered the wavelengths of the laser beams in a way that allowed them to transfer energy from one beam to another. The fix required tweaking the beams’ wavelengths by mere angstroms — tenths of a billionth of a meter.

“Engineering-wise, that’s amazing they could do that,” says physicist Carolyn Kuranz of the University of Michigan in Ann Arbor, who was not involved with the work. What’s more, “these tiny, tiny tweaks make such a phenomenal difference.”

After all the adjustments, the ensuing fusion reactions yielded 3.15 million joules of energy — about 1.5 times the input energy, Kritcher and colleagues reported in Physical Review E . The total energy needed to power NIF’s lasers is much larger, around 350 million joules. While NIF’s lasers are not designed to be energy-efficient, this means that fusion is still far from a practical power source.

Another experiment in July 2023 used a higher-quality diamond capsule and obtained an even larger energy gain of 1.9, meaning it released nearly twice as much energy as went into the reactions ( SN: 10/2/23 ). In the future, NIF researchers hope to be able to increase the laser’s energy from around 2 million joules up to 3 million , which could kick off fusion reactions with a gain as large as 10.

What’s next for fusion

The researchers also discovered a long-predicted phenomenon that could be useful for future experiments: After the lasers heated the hohlraum, it was heated further by effects of the fusion reactions, physicist Mordy Rosen and colleagues report in Physical Review Letters .

Following the implosion, the ignited fuel expanded outward, plowing into the remnants of the diamond shell. That heated the material, which then radiated its heat to the hohlraum. It’s reminiscent of a supernova, in which the shock wave from an exploding star plows through debris the star expelled prior to its explosion ( SN: 2/8/17 ).

“This is exactly the collision that’s happening in this hohlraum,” says Rosen, of LLNL, a coauthor of the study. In addition to explaining supernovas, the effect could help scientists study the physics of nuclear weapons and other extreme situations.

NIF is not the only fusion game in town. Other researchers aim to kick off fusion by confining plasma into a torus, or donut shape, using a device called a tokamak. In a new record, the Joint European Torus in Abingdon, England, generated 69 million joules , a record for total fusion energy production, researchers reported February 8.

After decades of slow progress on fusion, scientists are beginning to get their atomic orchestras in sync.

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Scientists achieve a breakthrough in nuclear fusion. Here’s what it means.

A U.S. lab has successfully sparked a fusion reaction that released more energy than went into it. But there’s still a long way to go toward fusion as a clean energy source.

For more than 60 years, scientists have pursued one of the toughest physics challenges ever conceived: harnessing nuclear fusion, the power source of the stars , to generate abundant clean energy here on Earth. Today, researchers announced a milestone in this effort. For the first time, a fusion reactor has produced more energy than was used to trigger the reaction.

On December 5, an array of lasers at the National Ignition Facility (NIF), part of the Lawrence Livermore National Laboratory in California, fired 2.05 megajoules of energy at a tiny cylinder holding a pellet of frozen deuterium and tritium, heavier forms of hydrogen. The pellet compressed and generated temperatures and pressures intense enough to cause the hydrogen inside it to fuse. In a tiny blaze lasting less than a billionth of a second, the fusing atomic nuclei released 3.15 megajoules of energy—about 50 percent more than had been used to heat the pellet.

Though the conflagration ended in an instant, its significance will endure. Fusion researchers have long sought to achieve net energy gain, which is called scientific breakeven. “Simply put, this is one of the most impressive scientific feats of the 21st century,” U.S. Energy Secretary Jennifer Granholm said at a Washington, D.C. media briefing.

In reaching scientific breakeven, NIF has shown that it can achieve “ignition”: a state of matter that can readily sustain a fusion reaction. Being able to study the conditions of ignition in detail will be “a game-changer for the entire field of thermonuclear fusion,” says Johan Frenje, an MIT plasma physicist whose laboratory contributed to NIF’s record-breaking run.

The achievement does not mean that fusion is now a viable power source. While NIF’s reaction produced more energy than the reactor used to heat up the atomic nuclei, it didn’t generate more than the reactor’s total energy use. According to Kim Budil, director of Lawrence Livermore National Laboratory, the lasers required 300 megajoules of energy to produce about 2 megajoules’ worth of beam energy. “I don’t want to give you the sense that we’re going to plug the NIF into the grid—that’s not how this works,” Budil added. “It’s a fundamental building block.”

Even so, after decades of trying, scientists have taken a major step toward fusion power. “It looks like science fiction, but they did it, and it’s fantastic what they’ve done,” says Ambrogio Fasoli, a fusion physicist at the Swiss Federal Institute of Technology in Lausanne.

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Sparking fusion ignition.

Though nuclear fusion and nuclear fission both draw energy from the atom, they operate differently. Today’s nuclear power plants rely on nuclear fission, which releases energy when large, heavy atoms such as uranium break apart due to radioactive decay. In fusion, however, small, light atoms such as hydrogen fuse into bigger ones. In the process, they release a small part of their combined mass as energy.

In laboratories, coaxing hydrogen nuclei to fuse into helium requires creating and confining a “plasma”—an electrically charged gas, where electrons are no longer bound to atomic nuclei—at temperatures several times hotter than inside the sun. Scientists learned decades ago how to unleash this process explosively inside hydrogen bombs, and today’s fusion reactors can make it happen in a controlled way for fleeting instants.

Since the late 1950s and early 1960s, fusion reactors have had the same basic goal: create as hot and dense a plasma as possible, and then confine that material for long enough that the nuclei within it reach ignition. The trouble is, plasma is unruly: It’s electrically charged, which means it both responds to magnetic fields and generates its own as it moves. To support fusion, it has to reach truly staggering temperatures. Yet it’s so diffuse, it easily cools off.

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Physicist Riccardo Betti, an expert on laser-driven nuclear fusion at the University of Rochester, likens the challenge of fusion ignition to burning gasoline in an engine. A small amount of gasoline mixes with air and then ignites from a spark. The spark isn’t massive, but it doesn’t have to be: All it has to do is ignite a small fraction of the gasoline-air mixture. If that tiny fraction ignites, the energy it releases is enough to ignite the rest of the fuel.

In terms of energy released, nuclear reactions pack roughly a million times more punch than chemical reactions do—and are vastly harder to get going. Past fusion experiments may have achieved the right temperatures or the right pressures or the right plasma confinement times to reach ignition, but not all those factors at once. “Basically, the spark was generated, but it wasn’t strong enough,” Betti says.

A pellet of fuel

NIF’s method of sparking the nuclear fuel starts with a peppercorn-size pellet that contains a frozen mix of deuterium and tritium, two heavier isotopes of hydrogen. This capsule is placed within a gold cylinder roughly the size of a pencil eraser that’s called a hohlraum, which is then mounted on an arm in the middle of a large, laser-studded chamber.

To trigger fusion, NIF fires 192 lasers all at once at the hohlraum, which angle into it through two holes. The beams then slam into the hohlraum’s inner surface, which causes it to spit out high-energy x-rays that rapidly heat up the outer layers of the capsule, making them burn off and fly outward. The inner part of this capsule rapidly compresses to nearly a hundred times denser than lead—which forces the deuterium and tritium inside to reach the temperatures and pressures needed for fusion.

In 1997, the National Academy of Sciences defined what “ignition” would mean for the facility , which broke ground that same year: when fusion energy released exceeds the energy of the lasers.The facility opened in 2009, and reaching this threshold ended up taking more than a decade. In August 2021, NIF reported its best-ever experimental run up to that point: 1.32 megajoules of released fusion energy for 1.92 megajoules of inputted laser energy.

The 2021 run signaled that ignition could be achieved within the NIF reactor. To finally cross the threshold, NIF researchers made a few minor tweaks, which included operating at slightly higher laser energies. “Any small changes, if you do them right, will have significant changes on the outcome,” Frenje says.

The dream of a fusion power plant

For all of NIF’s success, commercializing this style of fusion reactor wouldn’t be easy. Betti, the University of Rochester physicist, says that such a reactor would need to generate 50 to 100 times more energy than its lasers emit to cover its own energy use and put power into the grid. It’d also have to vaporize 10 capsules a second, every second, for long periods of time. Right now, fuel capsules are extremely expensive to make, and they rely on tritium, a short-lived radioactive isotope of hydrogen that future reactors would have to make on-site.

But most of these challenges aren’t unique to NIF, and the world’s many fusion labs and companies are chipping away at them. Last year the Joint European Torus (JET), an experimental reactor in Culham, England, set a record for the most fusion energy ever released during a single experimental run. Construction on JET’s successor— a huge international experiment known as ITER —is underway in France. And private companies in the United States and United Kingdom have built next-generation superconducting magnets, which could help create smaller, more powerful kinds of reactors.

It’s hard to say when, or even if, this work will yield a new energy future. But fusion researchers see the technology as an incredible tool for humankind whenever it’s ready—whether that’s 20, 50, or 100 years from now.

“When people say fusion is very complex, it’s true, but when people say that fusion is too complex, it’s not,” Fasoli says. “We know how to do complex things … Going to the moon is not simple. Achieving this result in fusion, it’s not simple. And we’ve demonstrated we can do it.”

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• 15 December 2023
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US nuclear-fusion lab enters new era: achieving ‘ignition’ over and over

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At the US National Ignition Facility in Livermore, California, 192 lasers (beamlines shown here) run into a target chamber (highlighted in blue) and focus on a capsule containing hydrogen isotopes. Credit: Damien Jemison/NIF/LLNL

In December 2022, after more than a decade of effort and frustration , scientists at the US National Ignition Facility (NIF) announced that they had set a world record by producing a fusion reaction that released more energy than it consumed — a phenomenon known as ignition. They have now proved that the feat was no accident by replicating it again and again, and the administration of US President Joe Biden is looking to build on this success by establishing a trio of US research centres to help advance the science.

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Nature 625 , 11-12 (2024)

doi: https://doi.org/10.1038/d41586-023-04045-8

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Correction 17 December 2023 : An earlier version of this article incorrectly stated the name of William & Mary.

Correction 19 December 2023 : An earlier version of this article incorrectly stated John Kerry’s title.

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Major Energy Breakthrough: Milestone Achieved in US Fusion Experiment

The National Ignition Facility achieves ignition in a fusion reactor.

An artist's rendering of the hohlraum and nuclear fusion reaction at the National Ignition Facility.

It was touted as a "major scientific breakthrough" and, it seems, the rumors were true : On Tuesday, scientists at Lawrence Livermore National Laboratory announced that they have, for the first time, achieved net energy gain in a controlled fusion experiment. 

"We have taken the first tentative steps toward a clean energy source that could revolutionize the world," Jill Hruby, administrator of the National Nuclear Security Administration, said in a press conference Tuesday.

The triumph comes courtesy of the National Ignition Facility at LLNL in San Francisco. This facility has long tried to master nuclear fusion -- a process that powers the sun and other stars -- in an effort to harness the massive amounts of energy released during the reaction because, as Hruby points out, all that energy is "clean" energy.

Despite decades of effort, however, there had been a major kink in these fusion experiments: the amount of energy used to achieve fusion has far outweighed the energy coming out. As part of the NIF mission, scientists had long hoped to achieve "ignition," where the energy output is "greater than or equal to laser drive energy." 

Some experts have remained skeptical that such a feat was even possible with fusion reactors currently in operation. But slowly, NIF pushed forward. In August last year, LLNL revealed it had  come close to this threshold by generating around 1.3 megajoules (a measure of energy) against a laser drive using 1.9 megajoules. 

But on Dec. 5, LLNL's scientists say, they managed to cross the threshold. 

They achieved ignition.

The target chamber at the National Ignition Facility.

All in all, this achievement is cause for celebration. It's the culmination of decades of scientific research and incremental progress. It's a critical, albeit small, step forward, to demonstrate that this type of reactor can , in fact, generate energy. 

"Reaching ignition in a controlled fusion experiment is an achievement that has come after more than 60 years of global research, development, engineering and experimentation," Hruby said.

"It's a scientific milestone," Arati Prabhakar, policy director for the White House Office of Science and Technology, said during the conference, "but it's also an engineering marvel."

Still, a fully operational platform, connected to the grid and used to power homes and businesses, likely remains a few decades away. 

"This is one igniting capsule at one time," Kim Budil, director of LLNL, said. "To realize commercial fusion energy you have to do many things. You have to be able to produce many, many fusion ignition events per minute, and you have to have a robust system of drivers to enable that." 

So how did we get here? And what does the future hold for fusion energy? 

Simulating stars

The underlying physics of nuclear fusion has been well understood for almost a century.

Fusion is a reaction between the nuclei of atoms that occurs under extreme conditions, like those present in stars. The sun, for instance, is about 75% hydrogen and, because of the all-encompassing heat and pressure at its core, these hydrogen atoms are squeezed together, fusing to form helium atoms.

If atoms had feelings, it would be easy to say they don't particularly like being squished together. It takes a lot of energy to do so. Stars are fusion powerhouses; their gravity creates the perfect conditions for a self-sustaining fusion reaction and they keep burning until all their fuel -- those atoms -- are used up.

This idea forms the basis of fusion reactors. 

A technician adjusts an optic inside the preamplifier support structure at the National Ignition Facility of the Lawrence Livermore National Laboratory.

Building a unit that can artificially re-create the conditions within the sun would allow for an extremely green source of energy. Fusion doesn't directly produce greenhouse gases, like carbon dioxide and methane, which contribute to global warming. 

And critically, a fusion reactor also doesn't have the downsides of nuclear fission, the splitting of atoms used in nuclear bombs and reactors today. 

In other words, a fusion power plant wouldn't produce the radioactive waste associated with nuclear fission.

The big fusion experiment

The NIF, which takes up the space of around three football fields at LLNL, is the most powerful "inertial confinement fusion" experiment in the world.

In the center of the chamber lies a target: a "hohlraum," or cylinder-shaped device that houses a tiny capsule. The capsule, about as big as a peppercorn, is filled with isotopes of hydrogen, deuterium and tritium, or D-T fuel, for short. The NIF focuses all 192 lasers at the target, creating extreme heat that produces plasma and kicks off an implosion. As a result, the D-T fuel is subject to extreme temperatures and pressures, fusing the hydrogen isotopes into helium -- and a consequence of the reaction is a ton of extra energy and the release of neutrons.

You can think of this experiment as briefly simulating the conditions of a star.

This metallic case, called a hohlraum, holds the fuel capsule for NIF experiments. 

The complicated part, though, is that the reaction also requires a ton of energy to start. Powering the entire laser system used by the NIF requires more than 400 megajoules -- but only a small percentage actually hits the hohlraum with each firing of the beams. Previously, the NIF had been able to pretty consistently hit the target with around 2 megajoules from its lasers. 

But on Dec. 5, during one run, something changed.

"Last week, for the first time, they designed this experiment so that the fusion fuel stayed hot enough, dense enough and round enough for long enough that it ignited," Marv Adams, deputy administrator at the NNSA, said during the conference. "And it produced more energy than the lasers had deposited."

More specifically, scientists at NIF kickstarted a fusion reaction using about 2 megajoules of energy to power the lasers and were able to get about 3 megajoules out. Based on the definition of ignition used by NIF, the benchmark has been passed during this one short pulse. 

You might also see that energy gain in a fusion reaction is denoted by a variable, Q. 

Like ignition, the Q value can refer to different things for different experiments. But here, it's referring to the energy input from the lasers versus the energy output from the capsule. If Q = 1, scientists say they have achieved "breakeven," where energy in equals energy out. 

The Q value for this run, for context, was around 1.5. 

In the grand scheme of things, the energy created with this Q value is only about enough to boil water in a kettle.

"The calculation of energy gain only considers the energy that hit the target, and not the [very large] energy consumption that goes into supporting the infrastructure," said Patrick Burr, a nuclear engineer at the University of New South Wales.

The NIF is not the only facility chasing fusion -- and inertial confinement is not the only way to kickstart the process. "The more common approach is magnetically confined fusion," said Richard Garrett, senior advisor on strategic projects at the Australian Nuclear Science and Technology Organization. These reactors use magnetic fields to control the fusion reaction in a gas, typically in a giant, hollow donut reactor known as a tokamak. 

Those devices have a much lower density than NIF's pellets, so temperatures need to be increased to well over 100 million degrees. Garrett said he does not expect the NIF result to accelerate tokamak fusion programs because, fundamentally, the two processes work quite differently. 

However, significant progress is also being made with magnetically confined fusion. For instance, the ITER experiment, under construction in France, uses a tokamak and is expected to begin testing in the next decade. It has lofty goals, aiming to achieve a Q greater than 10 and to develop commercial fusion by 2050.

The future of fusion

The experiment at NIF might be transformative for research, but it won't immediately translate to a fusion energy revolution . This isn't a power-generating experiment. It's a proof of concept.

This is a point worth paying attention to today, especially as fusion has often been touted as a way to combat the climate crisis and reduce reliance on fossil fuels or as a salve for the world's energy problems. Construction and utilization of fusion energy to power homes and businesses is still a ways off -- decades, conservatively -- and inherently reliant on technological improvements and investment in alternative energy sources.

Generating around 2.5 megajoules of energy when the total input from the laser system is well above 400 megajoules is, of course, not efficient. And in the case of the NIF experiment, it was one short pulse. 

View of an NIF laser bay from above. 

Looking further ahead, constant, reliable, long pulses will be required if this is to become sustainable enough to power kettles, homes or entire cities.

"It's unlikely that fusion power … will save us from climate change," said Ken Baldwin, a physicist at the Australian National University. If we are to prevent the largest increases in global average temperature, fusion power is likely going to be a little too late. 

Other investment is going to come from private companies, which are seeking to operate tokamak fusion reactors in the next few years. For instance, Tokamak Energy in the UK is building a spherical tokamak reactor and seeks to hit breakeven by the middle of this decade. 

Then there's Commonwealth Fusion Systems, spun out of MIT, which is hoping to generate around 400 megawatts of power, enough for tens of thousands of homes, by the 2030s. Modern nuclear power plants can produce almost three times as much.

And as CNET editor Stephen Shankland noted in a recent piece , fusion reactors will also need to compete against solar and wind power -- so even with today's revelatory findings, fusion energy remains entrenched in the experimental phase of its existence. 

But we can now cast one eye toward the future. 

It may not prevent the worst of climate change but, harnessed to its full potential, it could produce a near-limitless supply of energy for generations to come. It's one thing to think about the future of energy on Earth and how it will be utilized, but our eyes may fall on horizons even further out -- deep space travel could utilize fusion reactors that blast us well beyond the reaches of our sun's gravity, the very thing that helped teach us about fusion reactions, and into interstellar space. 

Perhaps then, we'd remember Dec. 5, 2022, as the first tiny step toward places we dared once only dream about.

Correction, 8:44 a.m. PT: This article initially misstated the amount of energy in the fusion reaction. NIF powered the lasers with about 2 megajoules and produced 3 megajoules as a result.

‘Breakthrough’ as fusion experiment generates excess energy for the first time

by Hayley Dunning , Laura Gallagher 13 December 2022

Scientists have hailed a ‘true breakthrough’ as a fusion reaction has successfully generated more energy than was used to create it.

For over seventy years, scientists have been attempting to harness thermonuclear fusion - the power source of stars - to generate energy.

This is a true breakthrough moment, which is tremendously exciting. Professor Jeremy Chittenden

Fusion has the potential to produce vast quantities of clean energy using few resources, requiring only a small amount of fuel and generating limited carbon emissions. Once a fusion plasma is ‘ignited,’ it will continue to burn for as long as it is held in place.

However, fusion reactions have proven difficult to control and no fusion experiment had previously produced more energy than had been put in to get the reaction going. At a press briefing today, it was announced that a fusion experiment at the National Ignition Facility (NIF) at Lawrence Livermore National Laboratory in the US has achieved this ‘holy grail,’ producing more energy than the laser pulse that was used to heat the fuel.

The energy in the laser pulse was 2.05 megajoules – equivalent to the energy of two Mars chocolate bars, or enough to boil six kettles of water. The energy from the fusion reactions was 50% higher than the energy of the laser pulse. It was released in the form of energetic neutrons.

Long sought-after goal

Imperial College London physicists are already helping to analyse the data from the successful experiment, which was conducted on 5 December 2022. Imperial has also produced more than 30 PhD students that have gone on to work at the NIF. The College retains strong links with the facility, and others throughout the world, through the  Centre for Inertial Fusion Studies  (CIFS). Professor Jeremy Chittenden , Co-Director of the Centre for Inertial Fusion Studies at Imperial College London, said: “Everyone working on fusion has been trying to demonstrate for over 70 years that it’s possible to generate more energy from fusion than you put in. This is a true breakthrough moment, which is tremendously exciting. It proves that the long sought-after goal, the ‘holy grail’ of fusion, can indeed be achieved. This brings us closer to generating fusion power on a much larger scale.  “To turn fusion into a power source we’ll need to boost the energy gain still further. We’ll also need to find a way to reproduce the same effect much more frequently and much more cheaply before we can realistically turn this into a power plant. It’s hard to say how quickly we might be able to get to that point. If everything aligns we could see fusion power in use in ten years, but it could take far longer. The key thing is that with today’s results we know that fusion power is within reach.” 

Dr Brian Appelbe , a Research Associate in the Centre for Inertial Fusion Studies at Imperial, said: “As well as being a significant step towards fusion power, this experiment is exciting as it will allow us to study matter at temperatures and densities never previously reached in the laboratory. All sorts of interesting Physics can occur at these conditions, such as the creation of antimatter, and the NIF experiments will give us a window into this world.”

Fusion fuel

The type of nuclear reaction that fuels current power stations is fission – the splitting of atoms to release energy. Fusion instead forces atoms of hydrogen together, producing a large amount of energy, and, crucially, limited radioactive waste.

There are two main ways researchers worldwide are currently trying to produce fusion energy. The NIF focuses on inertial confinement fusion, which uses a system of lasers to heat up fuel pellets producing a plasma – a cloud of charged ions.

The fuel pellets contain ‘heavy’ versions of hydrogen – deuterium and tritium – that are easier to fuse and produce more energy. However, the fuel pellets need to be heated and pressurised to conditions found at the centre of the Sun, which is a natural fusion reactor.

Once these conditions are achieved, fusion reactions release several particles, including ‘alpha’ particles, which interact with the surrounding plasma and heat it up further. The heated plasma then releases more alpha particles and so on, in a self-sustaining reaction – a process referred to as ignition.

Article text (excluding photos or graphics) © Imperial College London.

Photos and graphics subject to third party copyright used with permission or © Imperial College London.

Hayley Dunning Communications Division

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Laura Gallagher Communications Division

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Research , Pollution , Sustainability , Energy , Nuclear-energy , REF See more tags

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