Stabilization of Low-m Kink Modes in Tokamaks

Abstract

Numerical studies on magnetohydrodynamic (MHD) stability in a cylindrical tokamak are presented for various current profiles, including a hollow distribution. The stability to low-m external kink modes is found to be improved by concentrating the current density toward the center whilst keeping constant both the total current and the current density at the origin. The control of current profile is made through a new parameter which relates to the derivative of current density near the plasma surface. The effect of this parameter on tearing modes is also discussed when toroidicity and finite beta are taken into account.