中国“人造太阳”突破密度极限，聚变点火迎来新路径

Core Viewpoint - The research led by Professor Zhu Ping from Huazhong University of Science and Technology and Associate Professor Yan Ning from the Hefei Institute of Physical Science has made significant breakthroughs in the study of the Tokamak device, confirming the existence of a "density-free regime" and providing new pathways for fusion ignition [1][4][48]. Summary by Sections Breakthroughs in Tokamak Research - The study validates the boundary plasma-wall interaction self-organization (PWSO) theoretical model, confirming the mechanisms behind the long-standing density limit in Tokamak operations [3][4]. - The research demonstrates that the density limit, traditionally viewed as a hard boundary, can be surpassed, allowing for higher plasma density and improved fusion efficiency [4][41]. Understanding Density Limit - The density limit is a critical challenge in magnetic confinement nuclear fusion, as it directly impacts the conditions necessary for fusion reactions to occur, according to the Lawson Criterion [5][6]. - The Greenwald density limit, an empirical scaling law, has historically constrained Tokamak operations, with most devices operating below 1.0 times this limit [10][14]. PWSO Theory and Its Implications - The PWSO model shifts the perspective from viewing core plasma as an isolated fluid to a coupled self-organizing system with the device walls, highlighting the importance of plasma-wall interactions [16][18]. - The model introduces a new critical density limit that incorporates plasma transport parameters and wall interaction physics, revealing a complex relationship between critical density and various physical factors [22][23]. Experimental Validation - The EAST (Experimental Advanced Superconducting Tokamak) utilized its tungsten wall to conduct experiments that successfully crossed the Greenwald limit, maintaining electron density between 1.3 to 1.65 times the limit without experiencing disruptions [41][42]. - The experiments showed that under specific high-pressure conditions, increasing heating power led to a decrease in plasma temperature, effectively triggering the "switch" to enter the density-free regime [43][46]. Future Implications - The findings suggest that future fusion reactors could achieve high-density steady-state operations without the need for impurity injection, paving the way for breakthroughs in achieving fusion ignition and sustainable energy [47][48].