Scientists working with China's fully superconducting Experimental Advanced Superconducting Tokamak (EAST) have successfully reached a long-theorized "density-free regime" in fusion plasma experiments, breaking through a barrier that has limited fusion progress for decades.

The breakthrough experiment confirmed that plasma can remain stable even at extreme densities if its interaction with the reactor walls is carefully controlled. This finding removes a major obstacle that has slowed progress toward fusion ignition and brings humanity closer to clean, unlimited energy.

A Critical Milestone for Fusion Energy

Nuclear fusion is widely seen as a potential source of clean and sustainable energy. The process mimics what happens inside stars, where hydrogen atoms fuse together under extreme heat and pressure to form helium, releasing enormous amounts of energy. On Earth, scientists use powerful magnetic fields inside tokamak reactors to contain the superheated plasma needed for fusion.

For decades, researchers believed there was a fundamental limit to how dense plasma could become before it would become unstable and disrupt the fusion reaction. This "density limit" has been one of the biggest challenges in achieving sustained fusion reactions that produce more energy than they consume.

The research team, co-led by Professor Ping Zhu of Huazhong University of Science and Technology and Associate Professor Ning Yan of the Hefei Institutes of Physical Science at the Chinese Academy of Sciences, developed a new high-density operating approach for EAST. Their results, published in Science Advances, showed that plasma density can be pushed well past long-standing empirical limits without triggering the disruptive instabilities that usually end experiments.

While significant challenges remain before fusion power becomes a commercial reality, this breakthrough demonstrates that fundamental physics barriers previously thought insurmountable may have solutions. The work provides critical insights for the design of next-generation fusion reactors, including ITER currently under construction in France and future power plants.