Nuclear fusion milestone creates "burning plasma" for the first time
For the prospect of limitless, clean energy produced through nuclear fusion to become a reality, scientists need the reactions at the heart of the technology to become self-sustaining, and newly published research has edged them closer to that goal. Scientists using a high-powered laser at the National Ignition Facility in the US have achieved "burning plasma" for the first time, demonstrating for a fleeting moment how the fuel can provide much of the heat needed to keep the reactions going.
Scientists have been pursuing nuclear fusion technology at the National Ignition Facility since it came online in 2009, using 192 lasers housed inside a 10-story building to deliver 1.9 megajoules of ultraviolet energy onto a fuel capsule roughly the size of a ball bearing. This creates tremendous pressure and temperature that causes separate atoms to fuse into helium, a reaction that releases vast amount of energy.
This mimics the reactions that take place inside the Sun, but the trouble is creating them here on Earth requires huge amounts of energy to initiate the process. The overarching objective in this field is to have the fusion reactions become the primary source of heat instead, creating a self-sustaining form of nuclear fusion and ongoing energy production.
The results of experiments undertaken at the National Ignition Facility in November 2020 and February 2021 confirm small but critical steps toward this aim. The scientists made a few tweaks to the setup that included scaling up the amount of laser energy focused on the fuel, while changing the geometry of the target and the way energy is transferred between the laser beams. The result of this was a novel way to control the implosion process that compresses and heats the fuel, enabling the creation of self-heating plasma.
“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,” said lead author Annie Kritcher.
Though the lifetime of the plasma was measured in just nanoseconds, the achievement of burning plasma is a step toward nuclear ignition, where the process continues to fuel itself to produce energy. That reality is likely still decades away, but the scientists see these short-lived snippets of self-heating plasma as an important proof-of-concept.
“Fusion experiments over decades have produced fusion reactions using large amounts of ‘external’ heating to get the plasma hot," said lead author Alex Zylstra. "Now, for the first time, we have a system where the fusion itself is providing most of the heating. This is a key milestone on the way to even higher levels of fusion performance.”
The research was published in the journal Nature.