Modification of Toroidal Flow in the STOR-M Tokamak

Full text: Flow measurements using ion Doppler spectroscopy (IDS) have been recently used to study toroidal flow velocities of impurity ions. By selecting ion species, such as a CIII line (464.7 nm) with emission intensity peaking at the radial location near r = 7 cm, an OV line (650.0 nm) at, and CVI line (529.0 nm) near the plasma core, an estimated radial resolution of flow velocities can be achieved through a single line of sight along the tangential direction of the torus. During nominal ohmic discharges, the toroidal flow is in the counter-current direction in the core region at r ∼ 0 cm (CVI line) and r = 4 cm (OV line) and changes to co-current direction towards the edge at r = 7 cm (CIII line). In the extreme edge and scrape-off-layer (SOL), the flow is also in the co-current direction as measured by a movable Mach probe. Resonant magnetic perturbations (RMP) using a set of resonant helical coils in the m/n = 2/1 configuration or tangential compact torus injection changes the flow towards the co-current direction in all regions, while during the improved confinement phase triggered by fast gas puffing, the flow changes towards the counter-current direction. (author)