中国“人造太阳”实验，有新突破！

Core Viewpoint - The research team from the Hefei Institutes of Physical Science has confirmed the existence of a density-free zone in the EAST (Experimental Advanced Superconducting Tokamak), providing significant physical evidence for high-density operation in magnetic confinement nuclear fusion devices [1][5]. Group 1: Research Findings - The EAST device utilizes magnetic confinement to achieve controlled nuclear fusion, with plasma density being a critical parameter that directly affects fusion reaction rates [4]. - Previous research indicated a density limit where plasma would rupture and escape magnetic confinement, releasing significant energy and impacting device safety [4]. - The team developed a theory model called Plasma-Wall Self-Organization (PWSO), identifying the role of boundary impurities in triggering radiation instability that leads to the density limit [5]. Group 2: Experimental Methods and Results - By utilizing a fully metallic wall environment in EAST, the researchers employed methods such as electron cyclotron resonance heating and pre-filling gas to reduce boundary impurity sputtering, effectively delaying the onset of the density limit and plasma rupture [5]. - The physical conditions of the target plate were adjusted to reduce tungsten impurity sputtering, allowing plasma to surpass the density limit and enter a new density-free zone [5]. - The experimental results closely matched the predictions of the PWSO theory, marking the first confirmation of the existence of a tokamak density-free zone [5].