Inboard/outboard asymmetry of poloidal flow observed in the Compact Helical System

The poloidal flow velocity and the density of fully ionized carbon were measured in the Compact Helical System [K. Ida et al., Phys. Rev. Lett. 67, 58 (1991)] using the charge exchange spectroscopy with the bidirectional viewing. The poloidal asymmetry of the poloidal flow velocity observed in the outward shifted plasma is due to the electrostatic potential being constant on the magnetic flux surfaces. The poloidal asymmetry of the ion density can be explained by the conservation of the poloidal ion flux under the strong toroidal viscosity