‘Burning Plasma’ – New Discoveries in Fusion Reactions (Lawrence Livermore National Laboratory News Release)

The following is an excerpt from a news release published on November 14, 2022, by the Lawrence Livermore National Laboratory here.

Researchers at Lawrence Livermore National Laboratory (LLNL) have discovered that ions behave differently in fusion reactions than previously expected, thus providing important insights for the future design of a laser­–fusion energy source.

The findings are featured in a new paper in the Nov. 14 issue of Nature Physics and is titled “Evidence for suprathermal ion distribution in burning plasmas.”

The work shows that neutron energy measurements on the high-yield burning and igniting inertial confinement fusion experiments (ICF) showed that the average neutron energy produced is higher than expected for a deuterium-tritium (D-T) plasma that is in thermal equilibrium.

“This implies that the ions undergoing fusion have more energy than expected in the highest-performing shots, something that isn’t predicted — or able to be predicted — by the normal radiation hydrodynamics codes used to simulate ICF implosions,” said Alastair Moore, LLNL physicist and lead author of the paper.

While researchers don’t have a clear understanding of what is driving this observation, it is one of the most direct measurements of the ions undergoing fusion and is not captured by the simulations that are used to understand how to improve ICF implosions and deliver on the Lab’s mission generating a robust and reliable ignition platform.

In an article on the Vice news website Motherboard, physicist Alex Zylstra, who was one of the leaders of this study explained why these results were so significant.

He said that fusion normally requires that the fuel is heated to extremely high temperatures, “The significance of a burning plasma is that now the fusion itself is providing, actually, the majority of the heating of the fuel . . . Fusion is doing more heating than what we’re doing, and that’s a key scientific step on the way to getting the fuel to be able to become more self-sustaining.”