China's 'artificial sun' reactor exceeds major fusion density limit

China's EAST tokamak held plasma stably at about 1.3–1.65 times the Greenwald Limit, and the results were published Jan. 1 in Science Advances as evidence for a plasma‑wall self‑organization pathway to higher densities.

China's Experimental Advanced Superconducting Tokamak (EAST) has held plasma stably at densities beyond the commonly accepted Greenwald Limit. The research team reported maintaining plasma at roughly 1.3 to 1.65 times that limit. They reported that control of initial fuel gas pressure and electron cyclotron resonance heating helped manage plasma‑wall interactions. The findings were published Jan. 1 in Science Advances and are described as testing a theory called plasma‑wall self organization. Key facts: - EAST maintained stable plasma at about 1.3–1.65 times the Greenwald Limit. - Researchers adjusted initial gas pressure and electron cyclotron resonance heating to control plasma‑wall interaction. - The experiment reached a previously theorized "density‑free regime," reported under the plasma‑wall self organization (PWSO) framework. - Other teams have also reported Greenwald Limit breaches, including DIII‑D in 2022 and an experimental device at the University of Wisconsin–Madison in 2024. - The work was published Jan. 1 in Science Advances and was reported in a statement from the Chinese Academy of Sciences. Summary: The study is presented as evidence of a practical pathway for extending density limits in tokamaks and may inform design and operation of future fusion devices. Fusion research remains experimental and reactors typically consume more energy than they produce, so practical power plants are not immediate. International efforts such as ITER are intended to further test sustained fusion at larger scale, with ITER scheduled to begin producing full‑scale fusion reactions in 2039.