关键词: 限制器, 热斑, 烧蚀, EXL-50, 聚变装置

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