Breakthrough in nuclear fusion energy: Ignition confirmed in record 1.3 megajoule shot

The research has been published one year after the breakthrough was achieved. Will scientists be able to recreate it?
Loukia Papadopoulos
A nuclear breakthrough was achieved in August 2021.jpg
A nuclear breakthrough was achieved in August 2021.

James Wickboldt/LLNL 

  • In August 2021, a nuclear yield of more than 1.3 megajoules was achieved.
  • On the first anniversary of the event, papers were released describing it.
  • The event could revolutionize the industry.

Last year in August, a yield of more than 1.3 megajoules (MJ) was achieved at Lawrence Livermore National Laboratory’s (LLNL) National Ignition Facility (NIF) for the first time.

One year later

Exactly one year later, the scientific results of this record experiment have been published in three peer-reviewed papers: one in Physical Review Letters and two in Physical Review E, according to a press release by LLNL.

“The record shot was a major scientific advance in fusion research, which establishes that fusion ignition in the lab is possible at NIF,” said Omar Hurricane, chief scientist for LLNL’s inertial confinement fusion program.

“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.”

Breakthrough in nuclear fusion energy: Ignition confirmed in record 1.3 megajoule shot
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.”

Recreating the record-breaking performance

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

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“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.”

While the researchers have not been able to recreate the same level of fusion yield as the August 2021 experiment, all of them have showcased capsule gain greater than unity with yields in the 430-700 kJ range, significantly higher than the previous highest yield of 170 kJ from February 2021.

“It is extremely exciting to have an ‘existence proof’ of ignition in the lab,” Hurricane concluded. “We’re operating in a regime that no researchers have accessed since the end of nuclear testing, and it’s an incredible opportunity to expand our knowledge as we continue to make progress.”