Ion flow measurements in the vicinity of magnetic islands in DIII-D

Three-dimensional flows in the vicinity of magnetic islands have been imaged in the scrape off layer (SOL) for the first time in a tokamak. 3D flow measurements are essential to validate the numerical models used for developing island divertors for advanced stellarators like W7-X and to explain the resonant magnetic field (RMP) suppression of ELMs in future tokamak devices like ITER. In the case of island divertors, momentum loss from adjacent counterstreaming flows near magnetic islands can prevent access to the desired high-recycling regime [1, 2]. These flows have been observed experimentally in LHD [3] and HSX [1] and have been modeled extensively, along with 3D flows more generally, using the plasma fluid and kinetic neutral gas transport model EMC3-EIRENE [4, 1, 5, 6]. 2D and 3D measurements of the flow perturbation around magnetic islands has been achieved on DIII-D using Doppler Coherence Imaging measurements of C+ 2 impurity ions in the scrape off layer (SOL).