EAST集成型小ELM H模高Z金属杂质输运机理研究

高Z杂质输运一直是高参数、稳态长脉冲H模放电中的重要研究课题。在ELMy H-mode放电中，边界局域模带来的瞬时粒子流和热流轰击会导致第一壁高Z金属杂质进入主等离子体，这些高Z杂质的聚芯会带来严重的辐射功率损失并降低H模的约束性能和放电稳定性。对EAST上多种类型H模放电对比研究发现集成型小ELM（Integrated small-ELM,ISE）H模的杂质约束时间和整体辐射水平只与L模放电相当，同时可以维持较高的等离子体约束性能（H98~1.5, beta_N~1.5）。本项目将针对EAST ISE H模放电开展系统的实验研究，并结合边界与芯部杂质输运程序的模拟，理解这种模式下高Z金属杂质聚芯被抑制的物理机制，为EAST H模放电主动抑制高Z杂质提供物理依据。此项研究不仅有助于EAST实现高参数、稳态长脉冲的目标，而且对于将来ITER和CFETR高约束模式运行具有重要的参考意义。

High-Z impurities behavior is an essential issue must be concerned on approaching steady state high performance operation in future tokamak devices which have high-Z metal walls. The tungsten (W, Z=74) behavior in ELMy H-mode discharges is investigated on Experimental Advanced Superconducting Tokamak (EAST), which has a ITER-like tungsten divertor. The result shows a new regime of H-mode called integrated small-ELM (ISE) characterized by high q95, high radio-frequency (RF) heating power manifests an impurity confinement time and radiative power loss comparable to that of L-mode. The ISE H-mode also maintained a beta_N value ~1.5 which is apparent higher than that in high-enhanced-recycling (HER) and low-enhanced-recycling (LER) H-mode. In this item, combining the experiments and code modeling, deep investigations will be initiated for understanding the reason of impurity suppression in this H-mode regime and to push forward the high-Z impurity problem in steady state high performance operation in tokamak.