中国“人造太阳”实验，有了新进展！

Core Insights - The research team from the Hefei Institute of Physical Science, Chinese Academy of Sciences, has confirmed the existence of a density-free zone in the EAST (Experimental Advanced Superconducting Tokamak), which is crucial for high-density operation in magnetic confinement nuclear fusion [1][5]. Group 1: Research Findings - The tokamak device utilizes magnetic confinement to achieve controlled nuclear fusion, with plasma density being a key parameter that directly affects fusion reaction rates [2][3]. - Previous studies indicated a density limit for plasma, beyond which the plasma would break apart and escape magnetic confinement, releasing significant energy and impacting the device's safe operation [2][3]. - The research team developed a boundary plasma-wall interaction self-organization (PWSO) theoretical model, identifying the role of boundary impurities in triggering radiation instability at the density limit [5]. Group 2: Experimental Techniques - The team employed methods such as electron cyclotron resonance heating and pre-filling gas to reduce boundary impurity sputtering, actively delaying the onset of the density limit and plasma disruption [5]. - By adjusting the physical conditions of the target plate, the researchers managed to lower tungsten impurity-induced sputtering, allowing the plasma to surpass the density limit and enter a new density-free zone [5]. Group 3: Collaborative Efforts - This work was a collaborative effort involving the Hefei Institute of Physical Science, Huazhong University of Science and Technology, and Aix-Marseille University in France, supported by the National Magnetic Confinement Fusion Program [6].