Stability-transport modeling of the SINP tokamak discharges

A one-dimensional stability transport code has been developed to simulate t he evolution of tokamak plasma discharges. Explicit finite-difference metho ds have been used to follow the temporal evolution of the electron temperat ure equation. The poloidal field diffusion equation has been solved at ever y time step. The effects of MHD instabilities have been incorporated by sol ving equations for MHD mixing and tearing modes as and when required. The c ode has been applied to follow the evolution of tokamak plasma discharges o btained in the Saha Institute of Nuclear Physics (SINP) tokamak. From these simulations, we have been able to identify the possible models of thermal conductivity, diffusion and impurity contents in these discharges. Effects of different MHD modes have been estimated. It has been found that in low q (a) discharge m = 1, n = 1 and m = 2, n = 1 modes play major role in discha rge evolution. These modes are found to result in the positive jump in the loop voltage which was also observed in the experiments. Hollow current den sity profile j(phi) and negative shear in the p profile have also been foun d in the rising phase of a discharge.