Tokamak plasma equilibria with a zero total toroidal current

Several tokamak experiments have reported the existence of plasma equilibria with a zero total toroidal current in the AC operations of tokamaks. By taking a toroidal current profile model as a function of a quadratic polynomial of psi, a variety of equilibrium configurations with a zero total toroidal current have been found by solving the Grad-Shafranov equation numerically in the cylindrical coordinate system for the arbitrary cross section and finite aspect ratio. Results from different parametrizations of the current density (pressure) profile are discussed. Using input parameters consistent with experiments, some of the modeling results have been found to be in good agreement with experiment observations. (c) 2008 American Institute of Physics.