Sarah L. Nelson, Samantha L. Calkins and the National Ignition Team

For more than 60 years, scientists dreamed of a day when one of the most advanced scientific ideas in modern times might reach fruition: a nuclear ignition that creates more energy than it took to produce, a possibility with staggering real-world implications for abundant clean energy and national defense. 

On Dec. 5, 2022, Sarah Nelson and Samantha Calkins, two physical scientists working at the National Nuclear Security Administration, helped make this dream a reality by managing the program that performed the first controlled fusion experiment in history to reach what is known as scientific energy breakeven—a nuclear ignition that produced more energy than it took to complete the process.  

“This historic, first-of-its kind achievement has moved us from hope to confidence that there will be a commercially available clean energy source for future generations, which would be a game-changer for efforts to achieve a net-zero carbon economy,” said Michael Thompson, a principal deputy at the Department of Energy. 

Adding that the breakthrough will enable scientists to modernize nuclear weapons, he said Nelson and Calkins were both immersed in the technical work and oversaw the entire program, ensuring it had sufficient funding and that its different components were aligned. 

“The two women are representative of a couple of decades of federal folks who have supported and been engaged in keeping this program going until we could achieve significant results,” Thompson said. 

Overseeing the scientists and the science 

Mark Anderson, a senior advisor at the NNSA, said Nelson “runs a very complex office and oversees a wide number of programs and people, including federal program managers, the laboratories and senior leadership.” 

Calkins has “the most direct contact with the laboratories and has made sure the people doing the experiments have the resources and the capacity to achieve their goals,” he added. 

As Calkins described it, “I’m managing science and making sure that talented people can do good science.” 

The physical feat behind the achievement involves firing 192 laser beams into two small holes on the top and bottom of a small cylinder that is inside a facility the size of a sports stadium.  

When the beams hit their target, they unleash temperatures and pressures like those in the cores of stars and giant planets and inside exploding nuclear weapons. Although this outcome had been achieved more than a hundred times, never once before had the fusion fuel remained hot, dense and round enough for the time needed to ignite.  

This time the ignition created more energy than it took to fire the lasers: an energy breakthrough. The ramifications, however, lie well beyond the physics. 

A breakthrough for nuclear weapons and clean energy 

On the weapons front, the United States and other nuclear powers agreed in the 1990s to limit and, in many cases, ban nuclear testing, and the U.S. has not tested a nuclear weapon since 1992. Other nations, however, have been known to conduct underground tests, leading to a cat-and-mouse game of bragging or guessing.  

The fusion success shows the U.S. is capable of the most advanced nuclear developments on the planet without needing to prove it with detonation, Anderson said. He added that this success sends a powerful signal that the U.S. can maintain a safe, secure and reliable nuclear deterrent without a return to exploding nuclear weapons. 

As for clean energy, the fusion breakthrough is the first step in a long process to create reliable electricity without the release of greenhouse gases or radioactive waste by-products. 

Nelson said she finds it amazing that she got her start as an intern at the NNSA’s Lawrence Livermore Research Laboratory while finishing her undergraduate degree in chemistry. 

“It was a tremendously influential experience for me, but I had no idea that I’d be sitting in this chair 20 years later when such a scientific breakthrough would be accomplished.” Nelson said. “If we are able to use this technology someday to enable clean energy, this really would be tremendously game-changing.”