The extreme heat flux anticipated in fusion reactor divertor plasma facing components (PFCs) is perhaps the most challenging technology issue for fusion energy development. Most divertor PFCs are designed based on the maximum steady-state operational limits. Application of lithium (Li) in NSTX resulted in improved H-mode confinement, H-mode power threshold reduction, and reduction in the divertor peak heat flux while maintaining essentially Li-free core plasma operation even during H-modes. These promising Li results in NSTX and related modeling calculations motivated the passive and active radiative liquid lithium divertor concepts (RLLD and ARLLD) (Ono et al. in Nucl Fusion 53:113030, 2013; Fusion Eng Des 89:2838, 2014). This radiative process has the desired effect of spreading the localized divertor heat load to the rest of the divertor chamber wall surfaces, facilitating divertor heat removal with relatively small amount of lithium ~ few moles/s to handle the expected steady-state high divertor heat load. However, in addition to the high steady-state heat flux, the fusion reactor divertor PFCs could also experience significant transient heat flux such as ELMs and/or other magnetic reconnection events which can deposit large transient heat flux onto the divertor PFCs. If unprotected, it could damage the divertor PFC surfaces which could lead to a highly undesirable unplanned shutdown for PFC repair and/or replacement. In this paper, we explore feasibility of LLD and ARLLD concepts in handling such transient heat flux to protect the divertor PFCs from the extreme transient heat flux while maintaining the normal plasma operations. We also suggest a possible implementation technique using inductive pellet injector for the reactor PFC protection from transient heat flux which can be tested on NSTX-U.

中文翻译：

---

用于处理瞬态高热通量事件的有源辐射液态锂转向器

聚变反应堆偏滤器面向等离子体组件 (PFC) 中预期的极端热通量可能是聚变能源开发中最具挑战性的技术问题。大多数偏滤器 PFC 都是根据最大稳态操作限制设计的。锂 (Li) 在 NSTX 中的应用导致改进的 H 模式限制、H 模式功率阈值降低和偏滤器峰值热通量的降低，同时即使在 H 模式期间也能保持基本无锂的核心等离子体运行。NSTX 和相关建模计算中的这些有希望的 Li 结果激发了被动和主动辐射液态锂偏滤器的概念（RLLD 和 ARLLD）（Ono 等人，Nucl Fusion 53:113030, 2013; Fusion Eng Des 89:2838, 2014）。这种辐射过程具有将局部偏滤器热负荷分散到偏滤器室壁表面的其余部分的预期效果，使用相对少量的锂（约几摩尔/秒）促进偏滤器热去除，以处理预期的稳态高偏滤器热负荷. 然而，除了高稳态热通量之外，聚变反应堆偏滤器 PFC 还可能经历显着的瞬态热通量，例如 ELM 和/或其他磁重联事件，这些事件可以将大量瞬态热通量沉积到偏滤器 PFC 上。如果没有保护，它可能会损坏偏滤器 PFC 表面，这可能导致非常不希望的 PFC 维修和/或更换意外停机。在本文中，我们探索了 LLD 和 ARLLD 概念在处理此类瞬态热通量方面的可行性，以保护偏滤器 PFC 免受极端瞬态热通量的影响，同时保持正常的等离子体操作。我们还建议了一种可能的实施技术，使用感应颗粒喷射器来保护反应堆 PFC 免受瞬态热通量的影响，可以在 NSTX-U 上进行测试。