Steady state tokamak equilibrium with specified magnetic axis and two magnetic null points

An analysis method of tokamak plasma equilibrium by a relaxation method with specified magnetic axis and null points (two magnetic separatrix points) is developed. The six degrees of freedom due to designated positions of the magnetic axis and null points is possible by using six poloidal field coil currents. Stable steady state tokamak plasma equilibria are calculated along with the MHD (magnetohydrodynamic) potential energy. Assuming an RF heating plasma, the plasma generates a plasma current which partially or fully cancels the magnetic field from the poloidal field coils. For low-temperature plasmas, the plasma current distribution is centrally peaked; for high-temperature plasmas, the plasma current has a hole. A centrally peaked current distribution in a low-temperature plasma is evolved into a current distribution with a hole by increasing the plasma pressure by heating. These calculations show that, under sufficient heating, the pressure driven current in tokamak plasmas form a current hole which minimizes the MHD potential energy. (author)