China's fusion reactor exceeded the Greenwald density limit.

Researchers at the EAST tokamak report achieving a "density-free regime" that produced plasma densities about 65% above the Greenwald limit. The result, described in Science Advances, used controlled start-up conditions and plasma-wall self-organization.

Chinese scientists operating the Experimental Advanced Superconducting Tokamak (EAST) report a technical advance in controlling plasma density. Their study describes a density-free regime that allowed plasma densities about 65 percent above the Greenwald limit. The team achieved this by organizing plasma-wall interactions from start-up and by applying electron cyclotron resonance heating for each discharge. The work was published in the journal Science Advances. Key findings: - The experiments reached plasma densities roughly 65 percent beyond the Greenwald density limit. - Researchers used controlled initial fuel gas pressure and electron cyclotron resonance heating to enable plasma-wall self-organization (PWSO). - The reported state is described as a "density-free regime" achieved in the EAST tokamak at the Chinese Academy of Sciences. - EAST previously contained high-confinement plasma for nearly 17 minutes, improving on an earlier 403-second record. - The authors note remaining challenges, especially materials able to withstand long-term fusion conditions, and say lessons may apply to ITER, where China is a partner. Summary: The authors state the findings point to a practical pathway for extending density limits in tokamaks and future burning-plasma devices. The research team aims to reproduce the density-free regime under higher-performance plasma conditions. Many technical challenges remain, including developing materials for sustained fusion environments, and the results may inform work on ITER.