⚡ Nuclear fusion: China breaks the density barrier

Reproducing on Earth the reactions that power the Sun to create an abundant and clean energy source has been a long-standing goal. This quest for nuclear fusion has faced a major obstacle for decades: plasma density. Overcoming this obstacle without generating destructive instabilities had until now been a technical dream. A team of researchers has just achieved this feat.


Nuclear fusion requires heating a plasma to extreme temperatures, comparable to those at the heart of stars. The energy generated increases with the density of this plasma. However, beyond a certain threshold, violent disturbances appear, compromising the reactions and preventing the achievement of optimal yields.

Chinese scientists have just made a major breakthrough with the experimental reactor EAST. Using a new operational approach, they maintained a stable plasma at densities well above established limits. This work, published in Science Advances, indicates that it is possible to avoid destructive instabilities, marking an important step towards mastering fusion.

This experimental success is based on a recent theory: plasma-wall self-organization. Proposed by French physicists, it describes how a precise equilibrium between the plasma and the reactor's metal walls can enable operation where density is no longer limited. The results obtained on EAST provide the first confirmation, offering a renewed vision of these interactions.


To achieve this, the team carefully controlled the initial gas pressure and applied electron cyclotron heating from the start-up. This method reduces impurities and energy losses, allowing a gradual increase in density. The plasma thus reaches a stable state despite extreme conditions.

The project leaders specify that these results offer a concrete path to overcoming the density barrier in tokamaks. They plan to apply this technique during high-performance operations, aiming to achieve the regime under even more demanding conditions. Such an approach could accelerate the development of fusion.

This breakthrough reinforces hopes of one day achieving ignition, the stage where fusion durably produces more energy than it consumes.