In recent experiments of the HL-2A tokamak, the effect on the pedestal dynamics by the plasma fuelling with supersonic molecular beam injection (SMBI) has been intensively investigated. Experimental results in several tokamaks suggested that SMBI is a promising technique for ELM mitigation. In addition to the fuelling, the impact of impurities on the pedestal dynamics and instabilities has been investigated in HL-2A. Experimental results have shown that during the H-mode phase, a broadband electromagnetic (EM) turbulence was driven by peaked impurity density profile at the edge plasma region, and governed by double critical gradients of the impurity density. The absolute value of the threshold in positive gradient region is much lower than that in the negative region. This strong asymmetry in the critical gradients has been predicted by theoretical simulation. The results reveal that pedestal dynamics and heat loads can be actively controlled by exciting or changing pedestal instabilities.
在HL-2A托卡马克近期实验中，超声分子束注入（SMBI）等离子体加料对台基动力学的影响得到了深入研究。多个实验结果表明，SMBI是一种有前景的边缘局域模（ELM）缓解手段。除加料效应外，HL-2A装置还研究了杂质对台基动力学及不稳定性的影响。实验结果显示，在H模阶段，峰值杂质密度分布驱动了宽谱电磁湍流，该湍流受杂质密度的双临界梯度支配。正梯度方向的阈值绝对值显著低于负梯度方向。这种临界梯度的强不对称性已得到理论模拟的验证。研究结果表明，通过主动激发或改变台基不稳定性，可以有效控制台基动力学及热负荷。