EAST装置流动的液态锂限制器放电中锂的辐射屏蔽效应的实验及机理研究

Flowing liquid lithium wall not only can remove particle and heat flux from plasma bombardment, but also has a capability of self-healing of the damaged surfaces. This makes flowing liquid lithium wall attract more and more attention. Bombarded by plasma, eroded lithium resulting from evaporation and sputtering happens and lithium enters into plasma. At the edge region of plasma, lots of lithium condense and form lithium radiative shielding ring to shield heat flux and plasma particle flux including fueling and impurity particle, so it decreases heat and particle flux bombarded onto the first wall. The particle flux entering into plasma is probable to be effectively decreased due to decrease of particle flux released from the first wall and lithium shielding to the particle, which helps to reduce the particle recycling and impurity radiation in plasma and improve plasma confinement. These are beneficial for extending the lifetime of the first wall and the operation of high parameters and long pulse discharges. However, so strong lithium radiation also easily leads to plasma disruption. So it has to build a set of code to simulate lithium transport and distribution in plasma. Combined with the experimental data, it is to study lithium radiative shielding effect, shielding mechanism and the relation between lithium radiation and plasma compatibility. The mechanism of improved plasma performance by applying liquid lithium can be further refined. By the above research, it provides theoretical and experimental supports to assess the application of the flowing liquid lithium wall in the future fusion reactor.

流动的液态锂第一壁，能带走等离子体轰击产生的粒子流及热流，具有传统固态第一壁不具备的腐蚀自愈能力，越来越受到重视。在等离子体轰击下，从锂限制器表面腐蚀的锂进入到等离子体，在等离子体边界区域形成“辐射屏蔽带”，辐射屏蔽等离子体轰击到第一壁的热流及粒子流（燃料及杂质粒子），从而可能减少从壁上释放的燃料及杂质粒子的，有利于降低等离子体的再循环及杂质水平，提高等离子体性能，有利于延长第一壁的寿命及高参数长脉冲放电的运行。但过强的锂辐射也会引起等离子体的破裂，所以需要通过建立一套模拟锂在边界输运及辐射分布的数值模拟模型，结合实验数据，研究锂在边缘等离子体中输运过程及锂的辐射行为等;研究锂对等离子体的热流及粒子流的辐射屏蔽效应，进一步探索锂的辐射屏蔽机理;探索锂的辐射与等离子体兼容性的关系;完善液态锂对改善等离子体性能的工作机制。在此基础上，分析流动的液态锂第一壁在未来聚变装置的应用前景。

流动的液态锂第一壁，能带走等离子体轰击产生的粒子及热流，具有传统固态第一壁不具备的腐蚀自愈能力，越来越受到重视。通过本项目的支持，在EAST装置上成功地开展了基于薄膜流动的液态锂限制器实验。实验中在等离子体的边界区域观察到一个明亮的、空间分布不均匀的、绿色的锂辐射带，这些锂来自于等离子体轰击下限制器表面锂的被动注入及在刮削层的输运。锂的被动注入速率为>5×1020atom/s,通过蒸发、溅射及锂滴注入的方式进入等离子体。锂粒子很快被刮削层等离子体电离，并形成了一个从限制器表面开始的沿环向扩散的“辐射云”。锂的辐射云能够部分地隔离等离子体与壁材料，降低了杂质的释放，引起了等离子体约束性能的提升。同时锂的辐射有效地屏蔽了等离子体轰击产生的粒子流及热流，降低了第一壁的粒子轰击及热负荷，这种现象与其他低Z杂质注入引起的偏滤器脱靶现象类似。结合实验数据，通过SOLPS模拟的方式，研究了锂在边缘等离子体中的输运过程、锂在等离子体中的分布及锂的辐射深度及强度等；同时研究了锂的辐射对等离子体的粒子流及热流的屏蔽效应，明确了锂的辐射屏蔽的机理；完善了液态锂对改善等离子体性能的工作机制。我们在EAST装置上开展的流动液态锂壁实验研究，提高了流动液态锂作为未来聚变装置高热负荷区第一壁部件应用的可行性，为未来聚变装置第一壁提供新的选择，具有重要意义和前瞻性。