Ignition confirmed in record 1.3 megajoule shot

“Achieving the conditions needed for ignition has been a long-standing goal for all inertial confinement fusion research and opens access to a new experimental regime where alpha-particle self-heating outstrips all the cooling mechanisms in the fusion plasma.”

The papers outline the results from August 2021 that made the breakthrough possible.

The lab conducted experiments in the “burning plasma” regime for the first time, which set the stage for the record shot. Alex Zylstra, LLNL physicist, lead experimentalist, and first author of the experimental Physical Review E paper, noted in 2020 and early 2021.

“From that design, we made several improvements to get to the Aug. 8, 2021, shot,” he said. “Improvements to the physics design and quality of target all helped lead to the success of the August shot, which is discussed in the Physical Review E papers.”

Close up of atomic particle background science 3D illustration.

This experiment was then altered to include an improved target design.

“Reducing the coasting-time with more efficient hohlraums compared to prior experiments was key in moving between the burning plasma and ignition regimes,” said LLNL physicist Annie Kritcher, lead designer and first author of the design Physical Review E paper.

“The other main changes were improved capsule quality and a smaller fuel fill tube.”

Since their success last August, the researchers have been trying to recreate the record-breaking performance in order to understand its experimental sensitivities.

“Many variables can impact each experiment,” Kritcher said. “The 192 laser beams do not perform exactly the same from shot to shot, the quality of targets varies, and the ice layer grows at differing roughness on each target. These experiments provided an opportunity to test and understand the inherent variability in this new, sensitive experimental regime. “