Experimental study of the poloidal flow effect on magnetic island dynamics in LHD and TJ-II

The dynamics of a magnetic island is studied by focusing on the poloidal flows in the helical devices LHD and TJ-II. An experimental result implying the temporal increment of the E × B poloidal flow prior to the magnetic island transition from growth to healing is observed. The direction of the poloidal flow is in the electron-diamagnetic direction in LHD and in the ion-diamagnetic direction in TJ-II. From the magnetic diagnostics, it is observed that a current structure flowing in the plasma moves ∼π rad poloidally in the electron-diamagnetic direction during the transition in LHD experiments. These experimental observations from LHD and TJ-II show that the temporal increment of the poloidal flow is followed by the transition (growth to healing) of the magnetic island regardless of the flow direction and suggests the fact that a significant poloidal flow affects the magnetic island dynamics.