偏滤器等离子体中杂质对钨壁材料的侵蚀模拟研究

偏滤器是托卡马克中与等离子体直接接触的部件,为了保证装置的寿命,需要尽可能地减小等离子体对偏滤器靶板的侵蚀.本文用粒子模拟的方法研究了不同等离子体温度情况下碳和铍两种杂质离子对钨偏滤器侵蚀速率的影响.模拟首先得到稳定的鞘层结构、入射到靶板的离子流和能流密度,并通过统计获得了入射离子的能量和角度分布,最终根据这些物理参量,采用经验公式计算出钨靶板的侵蚀速率.研究表明,在等离子体温度不太高的情况下,钨靶板的热侵蚀几乎不起作用,而由于杂质离子对钨的物理溅射阈值较低,并且会通过鞘层加速获得能量,因此其对钨壁材料的物理溅射是导致靶板侵蚀的主要原因,另外靶板材料的侵蚀速率随着等离子体温度升高以及杂质含量增大而急剧增大.

Simulation of erosion of the tungsten wall by impurities in the divertor plasma

Divertor is a component that directly contacts the plasma in tokamak. To ensure the lifetime of the device, it is necessary to reduce the erosion of the divertor wall by plasma. In this work, a particle-in-cell model is used to study the influences of plasma temperature and impurity concentration on the erosion of tungsten divertor wall by carbon and beryllium ions. The steady-state sheath, particle and energy fluxes to the wall, and the energies and angle of the incident ions can be obtained. Then, these data can be used as the input parameters for the plasma-surface interaction model, to evaluate the erosion rate of the plate based on the empirical formulas for physical sputtering. It is found that the erosion by heating plays a negligible role under the plasma condition of this work. Due to the low physical sputtering threshold energy of tungsten by impurities and the impurity ions accelerated by sheath, the physical sputtering of the tungsten by the impurities plays an dominant role in the total erosion. In addition, the erosion rate increases with the increase of plasma temperature and impurity concentration.
Keywords： divertor plasma surface interaction particle-in-cell