In the face of rising global energy demands and mounting environmental pressures, the search for clean, safe, and sustainable energy sources has become a shared mission for scientists and policymakers around the world. Nuclear fusion—an advanced energy technology still under development—is attracting significant attention across the U.S. and Europe. Thanks to its immense energy potential and near-zero carbon emissions, fusion is increasingly seen as a key breakthrough in the transition toward a sustainable energy future.
Fusion is the same energy process that powers the sun and other stars. When two light atomic nuclei, such as isotopes of hydrogen—deuterium and tritium—fuse under extremely high temperatures and pressures, they form a heavier nucleus, like helium, and release a tremendous amount of energy. This reaction produces vastly more energy than traditional fossil fuels or nuclear fission, and it does so without emitting carbon dioxide or generating long-lived radioactive waste.
Reproducing and controlling this stellar process on Earth is a dream that scientists have pursued for decades. To make it possible, researchers are developing methods to generate and maintain plasma—the ultra-hot, electrically charged state of matter where fusion occurs. In this state, atoms are stripped of their electrons, forming a mix of ions and free electrons that can be manipulated using powerful magnetic fields. Achieving and sustaining these conditions is the key challenge to unlocking controlled fusion energy.
The U.S. Department of Energy (DOE) has long invested in fusion research, playing a leading role in global efforts to make this technology viable. The federal government began supporting fusion in the 1950s through the Atomic Energy Commission, a predecessor to the DOE. Since then, the DOE’s Office of Science, through its Fusion Energy Sciences (FES) program, has continued to support fundamental research while collaborating on major international projects, most notably ITER.
ITER, based in France, is the world’s largest magnetic confinement fusion experiment. Its core device, known as a tokamak, uses a donut-shaped magnetic field to confine plasma long enough for sustained fusion reactions to occur. Unlike smaller experimental tokamaks around the world—including U.S. facilities such as the DIII-D National Fusion Facility—ITER aims to achieve a "burning plasma," where the plasma is heated mainly by its own fusion reactions rather than external sources. DOE is a major contributor to ITER, and its involvement underscores America’s commitment to advancing global fusion science.
In addition to tokamak research, U.S. institutions are exploring alternative confinement systems. The Princeton Plasma Physics Laboratory, for instance, is developing a device called a stellarator. Unlike the symmetrical design of tokamaks, stellarators use complex, twisted magnetic fields to confine plasma without requiring constant current. Although technically more challenging to build, stellarators offer the promise of longer, steadier plasma confinement, which could make them more suitable for continuous fusion energy production.
Beyond magnetic confinement, the U.S. has also achieved groundbreaking results in inertial confinement fusion (ICF). This approach uses intense laser beams to compress and heat a tiny fuel pellet, initiating fusion. The National Ignition Facility (NIF) at Lawrence Livermore National Laboratory is the world’s most advanced ICF facility. It fires 192 lasers at a tiny target containing frozen hydrogen isotopes, creating a burst of X-rays that cause the target to implode. This process generates extreme temperatures and pressures—similar to those inside stars and nuclear weapons—and triggers a fusion reaction before the fuel can disperse.
In 2022, NIF achieved a historic milestone: ignition. For the first time, a laboratory fusion reaction produced more energy than the laser energy delivered to the target. This long-anticipated breakthrough represents a major scientific triumph, especially for the National Nuclear Security Administration's Stockpile Stewardship Program, which maintains the U.S. nuclear arsenal without explosive testing. Since then, ignition has been successfully repeated multiple times, validating the experiment and boosting confidence in fusion’s future as an energy source.
Fusion’s potential goes far beyond electricity generation. It offers a future energy source that could simultaneously provide high-grade heat for hydrogen production, support industrial processes, power water desalination systems, and enable carbon capture technologies. Deuterium is abundantly available in seawater, and tritium can be bred within fusion reactors using lithium, potentially creating a closed fuel cycle that reduces dependency on scarce resources.
However, significant technical hurdles remain. One of the most pressing challenges is the development of materials that can withstand the extreme environment inside a fusion reactor. The high-energy neutrons generated during fusion can damage reactor walls over time, causing structural degradation. As a result, researchers are working to develop new, radiation-resistant materials that can maintain performance over extended operation periods.
Managing radioactive waste is another consideration. While fusion does not produce long-lived radioactive byproducts like fission, some structural components can become temporarily activated by neutron bombardment. Developing efficient recycling and short-term storage solutions is essential to mitigate environmental risks.
Fuel cycle management is also a critical issue. Tritium, although used in small quantities, is radioactive and scarce in nature. Establishing a reliable breeding and handling process within the reactor is necessary to support continuous operation.
In addition, fusion reactors require integration of multiple high-performance systems, including vacuum chambers, superconducting magnets, radiofrequency heating, and advanced diagnostics—making system engineering an enormous challenge.
To address these gaps and accelerate commercialization, DOE launched several high-risk, high-reward funding initiatives through its Advanced Research Projects Agency–Energy (ARPA-E) beginning in 2015.
These programs focus on supporting innovative technologies and startups that explore more compact, efficient, and deployable fusion systems. Private-sector engagement has since expanded significantly, with several fusion startups securing public and private funding to develop next-generation prototypes.
This fusion innovation ecosystem is not limited to government labs. It includes a growing community of researchers, engineers, and young scientists. One such scientist, Alexandra LeViness, a former graduate student at the Princeton Plasma Physics Laboratory, has worked hands-on with components of a stellarator—a large, intricately coiled fusion device. In a striking image, she stands beside a massive metallic assembly, a ribbed copper segment rising above her head, symbolizing the human ambition to harness the forces of the cosmos.
The push toward fusion energy also requires a responsible approach to risk management, especially regarding nuclear nonproliferation. While fusion itself does not involve fissile materials, some experimental configurations may raise concerns about materials handling or neutron activation.
The U.S. and its partners maintain strict oversight and international cooperation to ensure that fusion development aligns with peaceful objectives.
Through continued innovation, robust international partnerships, and bold strategic investments, the U.S. and European nations are working to bring fusion energy from scientific theory to industrial reality.
While commercial fusion power is still on the horizon, recent breakthroughs have turned what was once thought of as science fiction into a credible path forward. As these efforts continue, fusion may well emerge as one of the most transformative clean energy sources of the 21st century.