The aim of this paper is to estimate the effects of usual drifts and gas puffing/pumping locations on divertor detachment and Ar ion transport in the Experimental Advanced Superconducting Tokamak (EAST) by using the edge plasma code package SOLPS5.1. The simulated results reveal that which target plate first detaches depends strongly on the usual drifts, but not on the location of impurity gas puffing, which could be one of the possible explanations for the experimentally observed phenomenon (Chen et al 2013 Phys. Plasmas20 022311) that the lower inner target first detached compared to the lower outer target with the lower outer gas puffing. The physics behind this phenomenon is that drifts not only can induce background ion flux, plasma density and temperature redistribution in the scrape-off layer (SOL) and divertor region, but also can change the Ar impurity force balance leading to Ar ions being dragged from bottom to top. Furthermore, the simulated results illustrate that the Ar ion transport in the SOL and divertor region is similar for different gas puffing locations including upstream and divertor region before partial detachment. However, the Ar ions penetrate into the core more easily, giving rise to more discharge disruption during complete detachment with upstream gas puffing than with divertor region puffing. Finally, we also estimate the effect of gas pumping on the detachment in order to realize long-pulse partial detachment in EAST. The results indicate that long-pulse partial detachment could be obtained by improving the pumping speed to match the puffing speed in case the excess Ar atoms accumulate in the core plasma during partial detachment in EAST.
本论文旨在利用边界等离子体代码包SOLPS5，评估在实验先进超导托卡马克（EAST）中，通常漂移以及充气位置对偏滤器脱靶和Ar离子输运的影响。模拟结果表明，哪个靶板首先脱靶强烈依赖于通常漂移，而非杂质充气位置，这可能是对实验观测现象（Chen等人，2013，Phys. Plasmas 20, 022311）的一种可能解释，即在下外充气条件下，下内靶首先脱靶。这一现象背后的物理机制在于，漂移不仅能引起刮削层（SOL）和偏滤器区域中背景离子通量、等离子体密度和温度的重新分布，还能改变Ar杂质的力平衡，导致Ar离子从底部被拖拽至顶部。此外，模拟结果还表明，在部分脱靶之前，不同充气位置（包括上游和偏滤器区域）下，SOL和偏滤器区域中的Ar离子输运行为相似。然而，在上游充气时，Ar离子更容易穿透至芯部，从而在完全脱靶期间引发更强的放电破裂风险。最后，我们还评估了抽气对脱靶的影响，以实现EAST中的长脉冲部分脱靶。结果表明，通过提高抽气速率以匹配充气速率，可以避免在部分脱靶期间过量Ar原子在芯部积累，从而获得长脉冲部分脱靶。