The untold history behind fusion ignition

On December 5, 2022, researchers at the National Ignition Facility achieved a major milestone in plasma physics: nuclear fusion ignition. For the first time, a laboratory fusion reaction created more energy than it consumed.

While the experimental run that reached ignition took just nanoseconds, it was built on more than 50 years of research. That history was presented by Mordecai Rosen, who played a key role in all that work leading up to ignition. He not only detailed the technical work of the experiments, but also the personal stories of researchers involved, some of whom have been nearly forgotten to history.

Rosen cited several key lessons that were learned along the way, including international collaboration, which was increased by efforts to declassify the research in the 1990s, and external advice, which helped shape an approach that ultimately enabled ignition. Perhaps foremost in the journey to ignition was the inherent flexibility of inertial confinement fusion (ICF), which can vary how the fuel targets are compressed.

“The big picture lesson learned is the beauty of ICF, with its superpower — the ability to innovate,” Rosen said. “It helped us circumvent the stumbling blocks that we discovered along the way and make progress.”

While ignition has been achieved, the journey is by no means over. Proposed upgrades to the facilities could see gains improved by an order of magnitude.

“We’ve only just begun,” Rosen said. “All of this work is just what’s required to get to the next steps that we’ve always wanted, which is a much larger laser that could get us gigajoules of gains.”

Source: “The long road to ignition: An eyewitness account,” by Mordecai D. Rosen, Physics of Plasmas (2024). The article can be accessed at https://doi.org/10.1063/5.0221005 .