Study of Magnetohydrodynamic Stability in Damavand Tokamak with Large Aspect Ratio

Ideal magnetohydrodynamic (MHD) equilibrium is vulnerable to numerous unstabilizing mechanisms. Instabilities introduce distortions to the plasma magnetic surfaces and their boundaries, their driving force being the radial gradient of plasma toroidal current density. For certain modal numbers, internal kink modes may develop, and their study is feasible according to the energy principle, in which the change in total potential energy is evaluated due to the disturbance. In this paper, we present a new analysis of MHD equilibrium and stability, and apply it to Damavand Tokamak which has a large aspect ratio. For this purpose, we combine the perturbation and Green's function methods to solve the equilibrium configuration problem. At this stage, plasma profiles are found explicitly in terms of Bessel functions, and we present a simple expression for estimation of total toroidal plasma current. Then the rest of plasma profiles, including poloidal magnetic flux, safety factor, and toroidal current density, are obtained and plotted. In the next step, we turn to the stability calculations and characterize the stable and unstable ideal MHD modes of Damavand plasma.