Nuclear Fusion Threshold Crossed

One of the last remaining milestones in fusion research before attaining ignition and self-sustaining energy production is creating a burning plasma. In this state, the fusion reactions themselves become the dominant source of heating in the plasma, but do not yet overcome all mechanisms of energy loss.

A burning plasma state was achieved on November 2020 and February 2021 at Lawrence Livermore National Laboratory’s National Ignition Facility (NIF), the world’s most energetic laser.

The work, which focuses on the designs that led to these results, is featured in the Jan. 26 issue of Nature titled “Design of inertial fusion implosions reaching the burning plasma regime,” with LLNL physicists Annie Kritcher and Chris Young serving as lead authors.

“In these experiments we achieved, for the first time in any fusion research facility, a burning plasma state where more fusion energy is emitted from the fuel than was required to initiate the fusion reactions, or the amount of work done on the fuel,” Kritcher said.

This was achieved through an energy feedback process called self-heating, where the fusion plasma heats itself. When the energy from self-heating is dominant over the energy that was injected to initiate the fusion reactions, the plasma enters a burning plasma state. Creating this new regime in a controlled laboratory setting is of great scientific importance for fundamental fusion research as well as supporting the National Nuclear Security Administration’s science-based Stockpile Stewardship program. This work also was the basis for the recent monumental success of NIF in achieving 1.35 MJ in the laboratory for the first time. This accomplishment also validates the work done decades ago to establish the power and energy specifications for NIF.


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