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中国物理学会期刊

聚变装置不同壁处理涂层在氘粒子轰击下的物理溅射行为模拟研究

CSTR: 32037.14.aps.74.20250805

Simulation study of physical sputtering behavior of different wall conditioning layers in fusion devices under deuterium particle bombardment

CSTR: 32037.14.aps.74.20250805
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  • 聚变装置表面涂覆壁处理如锂化、硼化、硅化等形成的涂层在高能氘粒子的轰击下会因为物理化学溅射损失, 从而使壁条件变差, 影响等离子体放电性能. 为了评估不同壁涂层的溅射损失行为, 本文采用两体碰撞近似模型, 对以碳、钨为基材的锂、硼和硅涂层材料在氘粒子轰击下的物理溅射行为进行了模拟分析. 结果表明, 因锂具有低的表面结合能而硅具有高的原子序数, 锂和硅分别在一定入射条件下溅射产额最大. 对于双层靶, 钨基涂层的溅射产额在特定能量出现剧增, 主要是由于钨溅射阈值高, 入射粒子在钨界面被大量反射, 并且具有较高的能量. 最后, 由于靶表面成分会随着入射通量增加而变化, 涂层材料的溅射产额也随之变化. 本研究为聚变装置壁处理涂层寿命的评估提供数据支持, 并为壁处理涂层材料设计及处理策略提供了重要的理论参考.

     

    Wall conditioning coatings—lithium (Li), boron (B) and silicon (Si)—introduced by lithiumization, boronization, or siliconization, serve as a critical strategy for suppressing fuel recycling and reducing impurity fluxes from the wall of a tokamak. These techniques directly improve plasma initiation, reproducibility, energy confinement, and operational stability in fusion devices. However, these coatings undergo both physical and chemical sputtering by boundary plasma bombardment. This erosion behavior critically determines coating lifetime and, consequently, long-pulse plasma performance. To evaluate the influence of physical sputtering on coating durability and to compare material-specific differences, binary collision approximation (BCA) simulations are conducted to investigate the physical sputtering behaviors of Li, B, and Si coatings. Carbon (C) and tungsten (W) substrates are also modeled to assess interface effects. The results reveal the significant differences in sputtering yields between Li, B, and Si in incident angles and deuterium energies. Owing to its low surface binding energy, lithium exhibits the highest sputtering yield at large angles and low energies, while silicon, with the highest atomic number, presents the highest sputtering yield at small angles and high energies. Sputtering yields of carbon-based and tungsten-based coatings vary with angle and energy, driven by their differences of deuterium backscattering and substrate sputtering at the interface. Notably, for tungsten-based coatings, the sputtering yields increase dramatically at specific energies. This occurs because tungsten’s high surface binding energy causes incident deuterium atoms to reflect off the tungsten interface and then collide with coating elements. Consequently, when the energy transferred to the surface element is higher than its sputtering threshold, the sputtering yield increases. Additionally, increasing incident fluence modifies the target composition, leading to corresponding changes in the sputtering yields of coating materials. In summary, coating materials should be selected according to the expected angle distribution and energy distribution of the incident plasma particles. To suppress the abrupt yield increase observed in tungsten substrates at specific energies, the coatings must be sufficiently thick. These findings provide a theoretical basis for selecting conditioning materials and optimizing wall conditioning strategies in fusion devices.

     

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