Disruption halo current rotation scaling on Alcator C-Mod and HBT-EP

Asymmetric halo currents (HCs) can exert large net forces on the vacuum vessel and other components during disruptions on tokamaks. The displacements caused by these forces can then be amplified if these asymmetric forces rotate at frequencies resonant with the vessel. This paper reports on the investigation of a recently proposed scaling law for the disruption HC rotation frequency that combines measurements on Alcator C-Mod with those on HBT-EP. We find that a new non-circular version of the scaling law ( *m/ \propto 1 B*T*(S/pi) ) takes into consideration the dependence of f_rot on the poloidal structure of the MHD instability (m) driving the asymmetry and describes the disruption-averaged rotation frequency on C-Mod. Disruption rotation is also found to be insensitive to the vertical position and impurity content of the plasma at the onset of the disruption.However, a stagnation in the time-evolution of f_rot is occasionally observed. Observations are consistent with the dominance of poloidal rotation during the disruption, which is motivated by the poloidal drift nature of the scaling law.托卡马克（tokamak）发生等离子体破裂时，不对称晕电流（HCs）会对真空室及其他组件施加巨大的净作用力。若这类不对称作用力的旋转频率与真空室固有频率发生共振，则其引发的位移会被进一步放大。本文针对一项新近提出的破裂晕电流旋转频率定标律展开研究，该定标律结合了阿尔卡特C-Mod（Alcator C-Mod）与HBT-EP两台托卡马克装置的实验测量数据。我们发现，该定标律的新型非圆截面形式（$m/f_{ ext{rot}} propto 1/B_T cdot (S/pi)$）兼顾了旋转频率$f_{ ext{rot}}$对驱动不对称性的磁流体动力学（MHD）不稳定性极向结构模数$m$的依赖关系，并能够描述阿尔卡特C-Mod装置上测得的破裂平均旋转频率。研究还发现，破裂发生时的旋转频率对等离子体破裂起始时刻的垂直位置与杂质含量不敏感。不过，研究中偶尔会观测到旋转频率$f_{ ext{rot}}$的时间演化出现停滞现象。观测结果与破裂过程中极向旋转占主导的结论相符，这一结论也得到了该定标律极向漂移特性的支撑。