Researchers at the brink of fusion ignition at National Ignition Facility

From 2011 to the present, the fusion yield (megajoules). Credit: LLNL
Inertial confinement fusion research has been ongoing for decades. A record yield of over 1.3 megajoules (MJ), from fusion reactions, was finally achieved in the laboratory during an experiment at Lawrence Livermore National Laboratory (LLNL) National Ignition Facility(NIF) on August 8, 2021. These results represent an 8-fold improvement on experiments performed in spring 2021, and a 25 percent increase over NIF’s 2018 record yield (Figure).

NIF precisely guides, amplifies and reflects 192 powerful laser beams onto a target approximately the same size as a pencil eraser. This is done in just a few billionthsof a second. NIF can generate temperatures of over 180 million F in the target and pressures of more that 100 billion Earth atmospheres. These extreme conditions cause hydrogenatoms in the target react with heat to create energy and fuse together.

Debbie Callahan, a LLNL physicist, will speak about this achievement at a plenary session of the 63rd Annual meeting of the APS Division for Plasma Physics. Although there has been extensive media coverage about this achievement, this talk will be the first chance to address these results in a scientific conference setting.

These large yields have been a goal for inertial confinement research since the beginning. It puts researchers at the threshold to fusion ignition. This is an important goal of NIF (the world's largest laser).

Although there are many technical definitions of ignition in the fusion community, the National Academy of Science adopted the "gain greater than unity" definition of ignition in 1997's NIF review. This refers to fusion yield greater that the laser energy delivered. This experiment yielded a fusion yield that was close to the goal of two-thirds of what was delivered by laser energy.

This experiment was built upon several innovations made by the NIF team over the past several years, including improved diagnostics, target fabrication improvements in capsule shell and fill tube, and hohlraum (a golden cylinder that holds target capsule), laser precision and design changes to increase energy coupled to the implosion.

These breakthroughs open up new research opportunities and allow for benchmark modeling to help understand the relationship between ignition and proximity.

Continue reading Uncovering the steady progress towards fusion energy gains