Effects of edge safety factor on the toroidal flow velocities during the resonant magnetic perturbations and compact torus injection experiments on the STOR-M tokamak

Abstract

ABSTRACTThe effects of the edge safety factor on the toroidal flow velocity modification due to resonant magnetic perturbation (RMP) and tangential compact torus injection (CTI) have been investigated on the Saskatchewan Torus-Modified (STOR-M) tokamak. The (l = 2, n = 1) RMP coils are wound against the outer surface of the vacuum vessel. The safety factor has been varied by changing the plasma current at a fixed toroidal magnetic field. As the edge safety factor is reduced, the magnetic perturbations on the q = 2 surface are expected to shift radially outwards, moving closer towards the RMP coils. The evolution of the plasma flow velocity was measured through ion Doppler spectroscopy (IDS). It has been found that RMP changes the flow velocity towards the direction of the plasma current direction and this effect is enhanced when the edge safety factor is reduced. When CT was injected tangentially along the plasma current direction, similar changes in the flow velocity have been found. However, the change is not sensitive to the edge safety factor in the CT injection case.