For decades, in the mountains of northern New Mexico, scientists at Los Alamos National Laboratory have pursued fusion energy, hoping to create in their experimental facilities the same clean, inexhaustible energy source that’s found inside the sun and stars. Despite recent breakthroughs, the goal remains elusive.
“For more than 60 years, there has been a worldwide quest to solve incredibly complex physics challenges and achieve controlled, peaceful fusion, which would transform our world’s energy needs,” says Mark Chadwick, interim deputy director for Science, Technology, and Engineering at Los Alamos. “It’s only in the realm of possibility because of the findings that took place at Los Alamos decades ago.”
In December 2022 and July 2023, Lawrence Livermore National Laboratory, with support from Los Alamos and other institutions, took a step forward in the journey. Scientists at Livermore’s National Ignition Facility (NIF) achieved what is called “fusion ignition”—when the energy from a controlled fusion reaction produces more power than it consumes. “Simply put, this is one of the most impressive scientific feats in the 21st century,” U.S. Secretary of Energy Jennifer Granholm said during a news conference. She called the laboratory-based fusion ignition a milestone that “moves us one significant step closer” to having zero-carbon fusion energy “powering our society.”
The NIF achievements are accompanied by other global fusion breakthroughs. In late 2021, the United Kingdom’s Joint European Torus (JET) produced the world’s greatest amount of fusion energy generated in a single experiment: 59 megajoules. In April 2023, China’s Experimental Advanced Superconducting Tokamak (EAST) set a record by generating and sustaining an extremely hot, highly confined plasma for nearly seven minutes—a crucial step for creating fusion energy. Across the world, the quest continues for this ultimate energy source.
If fusion energy could be produced on a large scale, it would be unlimited and inexpensive, plus it wouldn’t generate pollution. Unlike fossil fuels, fusion does not release carbon dioxide into the atmosphere. Also, fusion generates significantly less waste than nuclear fission reactions and poses no risk of nuclear meltdown. These qualities have inspired scientists to continue to look for ways to initiate and control fusion, despite the many challenges along the way.
So, what exactly is fusion?
Let’s circle back to the sun, the giant natural fusion reactor. In the sun’s core, immense gravity compresses rapidly moving atoms, causing them to mash together, or fuse, at high speeds and high temperatures, which, in turn, releases tremendous amounts of energy.
Most fusion experiments here on Earth use two kinds of hydrogen molecules: deuterium and tritium. Deuterium is found in sea water, and tritium can be generated from the element lithium, which is extracted from the ground. Deuterium and tritium are both positively charged and repel one another. Fusion researchers aim to keep the deuterium and tritium together (confine them under pressure) and create enough heat that the molecules collide and fuse, forming an electrically charged gas known as a plasma—the fourth state of matter. A successful fusion reaction creates what is called a burning plasma that emits great amounts of energy.
When comparing the amount of energy fusion reactions produce to fission reactions, which split atoms rather than combining them, fusion fuel is more potent and can generate four times as much energy by weight. Theoretically, fusion energy can be achieved using an extremely small amount of fuel. According to experts, a thimble of fusion fuel can potentially generate as much energy as 20 tons of coal. Einstein’s famous equation, energy equals mass times the speed of light squared, reveals that a small amount of mass can be converted into a large amount of energy. That’s the concept behind making fusion work.
Los Alamos’ contributions to the quest
The journey to create fusion in the laboratory has been fraught with setbacks—and also significant milestones. NIF’s recent ignition achievements reflect decades of fusion research, much of which has taken place at Los Alamos.
“Los Alamos has an extensive fusion research legacy,” says John Kline, director of Fusion Energy Sciences at the Laboratory. Many of the first breakthroughs took place in the 1940s during Project Y of the Manhattan Project (what would later become Los Alamos National Laboratory). The scientists working to build the first atomic bombs suggested creating a new, extremely powerful type of nuclear weapon— a thermonuclear weapon—by using a fission reaction to trigger a fusion reaction. In 1951, Los Alamos scientists proved this concept during Operation Greenhouse George, a nuclear test that resulted in the first terrestrial production of fusion energy.
“We produced more fusion than anyone could dream of,” Chadwick says of Greenhouse George. In 1952, scientists tested Ivy Mike, the world’s first thermonuclear device (essentially an undeliverable weapon, due to its massive size). Like Greenhouse George, Ivy Mike was detonated in the Enewetak Atoll in the Pacific Ocean.
In 1954, the B17 and B24 thermonuclear bombs, carried aboard the Convair B-36 Peacemaker aircraft, entered the U.S. nuclear stockpile. Fusion weapons have been part of America’s nuclear deterrent ever since.
While researchers were exploring ways to apply fusion to national security issues, they also delved into fusion energy experiments. In 1951, Los Alamos scientist James Tuck started the Lab’s fusion energy program by building a device he whimsically dubbed “the Perhapsatron.” This machine led to the development of the “pinch concept” to confine plasma and achieve fusion conditions. In the late 1960s and ’70s, Los Alamos built a set of fusion machines called the Scylla series, which also employed a related magnetic confinement “pinch” concept.
Another significant development in the Lab’s fusion energy history focused on using high-energy carbon dioxide laser systems to create fusion conditions. The last of these devices, named Antares, was commissioned in 1975 and terminated in 1985.
Although fusion energy research continues today at Los Alamos, much of the current fusion-focused work concentrates on national security applications. Ever since the 1992 moratorium on full-scale nuclear weapons testing, the United States has relied on nonnuclear and subcritical experiments coupled with advanced computer modeling and simulations to evaluate the health and extend the lifetimes of America’s nuclear weapons. This approach is called stockpile stewardship. Through fusion experiments, such as those at NIF, scientists have been able to create certain conditions needed to collect data for running computer simulations to evaluate America’s nuclear stockpile.
Los Alamos has an extensive fusion research legacy.”
“At Los Alamos, we are actively engaged in all aspects of fusion research,” says Charlie Nakhleh, associate Laboratory director for Weapons Physics. “Understanding fusion reactions and achieving ignition at NIF are important components of stockpile stewardship.”
The pursuit of fusion has also led to multiple breakthroughs in materials research, weapons technology, and the overall understanding of basic science and physics. “Fusion is a ‘grand challenge’ scientific problem that tests our codes, our people, our facilities, and our integrated capabilities,” Kline says.
Creating extreme conditions inside the laboratory also enhances research in other areas, according to Patrick Knapp, who leads the Pulsed Power Inertial Confinement Fusion and High Energy Density physics programs at Los Alamos. “We can use this capability to study all sorts of really exciting things like planetary formation, nuclear physics, atomic physics, solar physics, the list goes on and on,” he says. “We as a Laboratory are just starting to learn how to exploit this capability to answer important and exciting questions, and the possibilities are almost limitless.”
One goal, multiple approaches
So, how do scientists replicate the power of the sun inside a laboratory? The bottom line is finding a way to duplicate the intense heat, pressure, and confinement needed to maintain a fusion reaction long enough to produce energy. Scientists have experimented with two basic ways to do this: Inertial confinement fusion (ICF) and magnetic confinement fusion (MCF). Other approaches combine both inertial and magnetic concepts. At Los Alamos, scientists support research at other national laboratories and conduct their own fusion energy experiments.
Inertial confinement fusion
The basic idea behind ICF is to direct a large amount of energy at a tiny fuel target the size of a grain of rice. Scientists have experimented with a variety of ways to deliver that energy. Short pulses of electron beams, ion beams, and protons, as well as lasers have been used to generate the initial energy that sparks a fusion reaction.
NIF uses lasers as its initial energy source. The machine takes energy from a giant capacitor bank and transforms it into 192 pulsed laser beams focused onto a tiny target capsule that contains deuterium and tritium—aka the fusion fuel. The deuterium and tritium are forced together at enormous pressure and temperature. The result is a burning plasma, which is a critical step toward self-sustaining fusion energy.
Fusion is a huge, multinational problem with the potential to revolutionize global energy security and climate change."
That’s also what happened in December 2022 when NIF achieved ignition, an achievement that required the combined efforts of scientists from throughout the nuclear enterprise. Kevin Meaney, a Los Alamos plasma physics scientist, helped confirm the success of that experiment. His diagnostics measured how the fusion reaction progresses over time in the burning plasma. “Our measurements confirmed we are stepping into a new regime. The plasma is burning. It’s propagating. Being able to say that with confidence is thanks to Los Alamos diagnostics,” he says.
Nakhleh calls the ignition breakthrough “truly a national achievement. Los Alamos has been involved in the research on inertial confinement fusion for decades and has contributed to recent experiments and diagnostics on NIF in a significant and important way.”
Another approach to ICF is taking place at Sandia National Laboratories using a device called the Z Machine, named after the technique of using a Z pinch (zeta pinch) to compress plasma and create energy leading to a fusion reaction. Los Alamos scientists work with Sandia scientists to conduct experiments with the Z Machine.
“Getting data relies on large experimental facilities,” Meaney says. “These are the only facilities in the world that can make these conditions.”
Knapp says he is grateful to be able to conduct experiments with both the Z Machine and at NIF, but he is already looking toward the future. “The facilities we use today to study inertial confinement fusion are a long way off from facilities that will be needed for power generation,” Knapp says. “We need to learn how to operate much bigger facilities at much higher frequency—multiple times a second compared to once a day. These are huge challenges, but they are exciting ones.”
Magnetic confinement fusion
Magnetic confinement fusion uses magnetic fields to confine fusion fuel in the form of a plasma. Stellarators and tokamaks are two types of machines that use magnetic coils to contain plasma.
Glen Wurden, a longtime Los Alamos plasma physicist, frequently travels to Germany to conduct experiments on a stellarator device called the The Wendelstein 7-X fusion reactor. “We have been able to maintain a burning plasma for up to 30 minutes,” Wurden says, noting these international experiments advance many aspects of plasma physics.
Today, fusion looks more realistic than it did a decade ago. Every achievement is a stepping stone to answer questions and achieve a higher level of confidence.”
Tokamaks are doughnut-shaped machines that use magnetic fields to confine plasmas. This is the approach used by ITER, a multinational fusion research and engineering project underway in France. Originally an acronym for “International Thermonuclear Experimental Reactor,” project leaders now emphasize that “ITER” is Latin for “the way.” The United States is one of seven countries partnering on ITER. Since the initiation of the project, Laboratory scientists have participated in numerous efforts to support ITER’s development, including designing a system that will process and deliver deuterium and tritium to the facility, which is scheduled to begin operations in 2035.
The Plasma Liner Experiment and other combined approaches
Some experiments combine aspects of both magnetic and inertial confinement. Sandia has developed a technique called magnetized liner inertial fusion, or MagLIF, that uses an extremely high-current pulse to create a Z pinch magnetic field that crushes a preheated fuel-filled cylinder. These tests are being carried out using the Z Machine.
At Los Alamos, the Plasma Liner Experiment (PLX) uses plasma guns arranged in a sphere to fire ionized gas to compress and heat a pre-injected fusion fuel target plasma. Funded by the Department of Energy’s Advanced Research Projects Agency-Energy program, researchers are using the device to study plasma compression and heating. They will then compare their results with computer simulations to determine the viability of this approach.
“PLX is an innovative alternative concept that is still in the early stages,” explains Sam Langendorf, the Los Alamos physicist leading the project. He says the PLX approach could eliminate the need to rely on the solid fusion targets that get destroyed in other fusion devices, thus providing a more practical approach to fusion power. “With a plasma target you can envision how you can create an economical reactor.”
Although the Los Alamos PLX project will wrap up in 2024, Langendorf hopes that private industry will invest in similar programs.
Supporting research and development
Research on other fusion energy concepts and the technology that supports them is ongoing. “The pursuit of one thing leads to another thing,” Kline says. “Los Alamos works on key diagnostics, deuterium and tritium reaction history, neutron imaging, fusion rate as a function of time, and other diagnostics,” he says.
Because fusion reactors must be built from materials that can withstand high temperatures, irradiation, and stress, materials research and development is also needed. Lab scientists recently developed a new tungsten-based alloy that performs well in extreme environments. This alloy and similar materials bring researchers closer to their goal of building power plants that use fusion reactions to generate electricity.
“The new alloy has shown superior radiation tolerance and extraordinary potential,” says Osman El-Atwani, a former Los Alamos scientist instrumental in this research. Experiments conducted at Los Alamos’ Ion Beams Materials Laboratory have tested the alloy for irradiation resistance to ensure it can withstand the neutron damage that occurs in reactors.
“These newly developed tungsten-based high-entropy alloys are an important step to tame the harsh conditions faced by materials in fusion devices,” says Yongqiang Wang, a scientist who leads the Lab’s Radiation Science experimental team.
El-Atwani agrees, noting that “the development of this alloy, and the agreement between modeling and experimentation that it represents, points the way toward the development of further useful alloys, an essential step in making fusion power generation more robust, cost effective, economically predictable, and attractive to investors.”
Saryu Fensin, a team leader at the Lab’s Center for Integrated Nanotechnologies, adds that Los Alamos is uniquely positioned for this work. “We have expertise in studying materials under dynamic and temperature extremes—key to our core mission. We can now use that expertise in processing, characterization, irradiation, and mechanical testing to help the fusion community.”
Los Alamos scientists are also researching tritium—a radioactive isotope of hydrogen and one of the fuels required for many fusion designs. Tritium does not occur naturally. Currently, it is produced in the Tennessee Valley Authority’s Watts Bar Nuclear Plant and processed at the Savannah River Site in South Carolina. Understanding tritium behavior will play a crucial role in the success of fusion energy.
Researcher Victoria Hypes-Mayfield notes that there are a limited number of people who have the experience to design systems in line with tritium best practices. “Los Alamos has the knowledge to provide this expertise to the fusion community at large,” she says.
Exploration of other ways to use hydrogen in place of tritium is also underway, which would make some experiments safer and more economically feasible. “Reducing the amount of tritium held in a fusion power plant is a key consideration for bringing fusion devices to the grid,” says Hypes-Mayfield, who notes that “fusion is a huge, multinational problem with the potential to revolutionize global energy security and climate change. To be a part of the solution to such a wide-reaching problem is an awesome opportunity.”
What’s next? Bigger, better machines are necessary to conduct new types of experiments that would yield new data to advance our understanding of fusion.
“Right now, Los Alamos is partnering with Sandia to advocate for funding a next generation pulsed power facility that would be capable of demonstrating ignition and energy gain,” Knapp says. “This helps the nation diversify its technological paths to achieving necessary conditions in the laboratory for stockpile stewardship, and it also helps develop alternate paths that industry could benefit from. Pulsed power drivers are much more efficient at coupling energy to targets than lasers are. For a power plant, efficiency really matters, so understanding if it is possible to use this technology for fusion yield really benefits both missions.”
Meanwhile at NIF, scientists are outlining upgrades needed to generate more energy as well as update the aging device, which has been in operation since 2009.
As the national laboratories focus on expanding and upgrading their machines, they are also building new partnerships with private industry. “I am really excited about the prospects of collaborating with some of the private fusion companies that are out there,” Knapp says. “Given the pace at which these companies can innovate, we in the labs are likely to learn as much from them as they are from us.”
The future of fusion
As fusion research continues, scientists are exploring many areas where they can apply breakthroughs. For example, “fusion can be very useful for other purposes, such as fusion rocket engines for planetary defense,” Wurden says. When it comes to clean energy, however, he believes “that fusion energy for commercially competitive electricity is a long way off.”
Just how long is a long way off? Kline smiles, saying that scientists once claimed a working commercial fusion reactor was just 30 years away, but now “we’ve made significant progress. Now it’s only 20 years away,” he quips.
Despite the difficulty, scientists agree that fusion energy is no longer a question of if but rather when. “We are on a much more concrete path,” Meaney says. “Today, fusion looks more realistic than it did a decade ago. Every achievement is a stepping stone to answer questions and achieve a higher level of confidence.”
Kline agrees. “Energy is life,” he says. “Everybody needs electricity. Whether we solve the problem today or in 70 years, it’s still going to be of value.” ★