Abstract: ENN’s independently developed EXL-50, China’s first medium-scale spherical tokamak for exploratory experiments on commercial fusion power generation, encountered ablation of the copper-plated tungsten central column limiter during physical experiments, which is highly detrimental to stable plasma operation. Studies reveal that this phenomenon stems from two primary causes: First, installation deviations between the limiter and both the geometric axis of the central column and the magnetic field line axis expose the limiter to the strike zone of plasma magnetic field lines, subjecting it to meet intense thermal load impacts. Second,the limited bonding strength between the tungsten coating and copper substrate of the copper-plated tungsten limiter leads to ablation and spalling under repeated thermal load cycles. To fundamentally address the ablation issue, structural optimization and material upgrade of the limiter were implemented, accompanied by thermal-solid coupling field simulations under baking conditions. Results show that the optimized central column limiter meets requirements in both thermal performance and deformation control. Experimental verification confirms that the optimized structure exhibits no thermal spots or ablation phenomena.

Key words: Limiter, Thermal spot, Ablation, EXL-50, Fusion device

摘要： 由新奥集团自主研发设计的中等规模球形托卡马克聚变商用发电探索性实验装置玄龙-50(EXL-50)，在物理实验中出现铜镀钨中心柱限制器烧蚀现象，对等离子体稳定运行极为不利。经研究发现，此现象一方面是由于限制器与中心柱几何轴线及磁力线轴线的安装偏差，导致限制器暴露在等离子体磁力线的打击范围内而承受较大热负荷的冲击所致；另一方面是由铜镀钨限制器的钨涂层与铜基层的结合力有限，在热负荷反复冲击下，出现烧蚀剥落。为彻底解决烧蚀问题，对限制器进行了结构优化和材料升级，并模拟分析了烘烤工况下的热固耦合场。结果表明，优化后的中心柱限制器在热性能和变形量上均满足要求，实验结果也验证了优化后结构未出现热斑、烧蚀现象。

关键词: 限制器, 热斑, 烧蚀, EXL-50, 聚变装置