摘要:
在磁约束聚变等离子体装置中，面对等离子体的第一壁将直接影响高温等离子体性能及第一壁寿命，具有表面自我修复的、能有效抑制边界粒子再循环的液态金属锂第一壁越来越被重视，其中液态锂第一壁与等离子体相互作用的研究尤其重要。本文研究了HT-7装置液态锂限制器实验中锂的表面腐蚀及在装置内沉积特性、及其对等离子体性能影响。实验表明，当锂与等离子体相互作用较弱时，锂以微弱的蒸发及溅射形式从表面腐蚀并进入等离子体，表现为锂的线辐射有所增强，等离子体内杂质水平降低，氢再循环降低，有利于等离子体约束性能提高；当锂与等离子体间的相互作用比较强时，锂主要以锂滴形式直接进入等离子体，引起锂的辐射爆发，最终引发等离子体放电破裂。通过对锂斑及样品的分析发现，锂主要沉积在限制器周围，并且在低场侧及沿着等离子体电流方向沉积居多，表现为极向和环向分布不均匀，这也导致边界粒子再循环分布的不均匀。这些实验为研究液态锂第一壁与等离子体相互作用，分析液态锂第一壁在托卡马克装置上应用具有重要参考意义。
Abstract:
In the magnetic confinement fusion device, the first wall as plasma facing components will directly affect the performance of high temperature plasma. And the interaction of plasma and materials also affect the life of the first wall. Liquid lithium first wall receives more and more attention due to the properties of repairing itself and effectively inhibiting boundary particle recycling. So the research of the interaction between liquid lithium wall and plasma is particularly important. Erosion and deposition characteristics of lithium and its influence on the performance of plasma during lithium limiter experiment in HT-7 device are studied in-depth in this paper. Experimental results show that when the interaction between Li and plasma is weak, Li enters into the plasma mainly by weak surface evaporation and sputtering. During this process, Li line emission is strengthened, impurity and hydrogen recycling is decreased resulting in the improvement of plasma performance. When the interaction between Li and plasma becomes extremely strong, it is found so many big scale Li droplets ejected from liquid lithium surface to cause intense Li e?ux into plasma, leading to plasma discharge disruption. Li atoms coming from Li limiter are ionized in the scrape-off layer (SOL), and entered into hot plasma column as ions (Li+, Li2+, Li3+) and transported in plasma. After the experiment, it can be found that a lot of white spots distributed in the vacuum chamber wall, with its main composition being Li2CO3 by XPS analysis. Through observing Li spot distribution and analyzing the lithium film thickness by scanning electron microscopy (SEM) in different samples, it is observed that the lithium is primarily deposited around the limiter, but the number of Li spots is more at the low field side than that at the high field side of the device, and the Li film gradually becomes thinner along the toroidal direction of the HT-7 device, leading to the non-uniformity of impurity and hydrogen recycling. The experiment may provide a reference for studying the interaction of plasma and liquid lithium first wall and the application of liquid lithium first wall in future tokamak device.
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