IN August 2021, a nuclear fusion reaction triggered at the National Ignition Facility (NIF) in California, US, generated more energy than the energy that directly went into heating the target capsule where the reaction took place. Now, a year later, the team has confirmed that the reaction met another important milestone: ignition.
Ignition in fusion is defined by what is called the Lawson criterion, which is a figure of merit that compares the rate of energy generated by fusion reactions in the fusion fuel to the rate of energy losses to the environment. When the rate of production is higher than the rate of loss, the system will produce net energy. If enough of that energy is captured by the fuel to trigger fusion reactions within it, the system will become self-sustaining and is said to be ignited. This is exactly what happens when paper, wood, or coal is burnt: the heat from the burning part increases the temperature locally and sets fire to the adjacent, previously cold, fuel. The NIF uses the largest laser in the world to heat and compress a small capsule containing hydrogen fuel and thereby induce nuclear fusion reactions in the fuel.
Also read:The Science News Round-up
After the initial announcement about the fusion reaction last year, the researchers confirmed that the reaction achieved ignition according to nine different forms of the Lawson criterion. This makes the August 2021 fusion reaction the first laboratory fusion experiment to achieve ignition, bringing researchers another step closer to a Holy Grail of physics: nuclear fusion reactions that produce more energy than they consume. The achievement will have implications for nuclear fusion as a source of energy. The results were published in the August 8 issue of Physical Review Letters and Physical Review E.