Dependence of up–down asymmetry on the edge safety factor in the Saha Institute of Nuclear Physics–Tokamak (SINP–Tokamak)

Inside the limiter of Saha Institute of Nuclear Physics–Tokamak (SINP–Tokamak) [A. N. Sekar Iyengar, S. K. Majumdar, J. Basu, R. K. Paul, R. Pal, and S. Chowdhury, Pramana, J. Phys. 39, 181 (1992)] plasma potential was investigated using Langmuir probe arrays with poloidal and radial resolution and as a function of the safety factor at the limiter. A poloidal asymmetry was observed in floating potential in the edge region. Quantitatively, its up–down difference exhibits an almost square of safety factor divided by toroidal magnetic field-like scaling. A radial electric field, also observed in this region, was seen to increase with the edge safety factor. The plasma seems to be collisional here with the mean free path shorter than the connection length, where Pfirsch–Schluter current causes a qualitatively similar up–down asymmetry. However, its magnitude was seen to be much lower than the observed results. It has been shown that the presence of radial and/or toroidal component of the electric and magnetic...