Reduction Rate of the MHD Potential Energy by a Toroidal Plasma Current Drive during Tokamak Plasma Formation with DC_CS

Abstract

The reduction rate of the magnetohydrodynamic (MHD) potential energy δW_M is defined as the energy difference between the vacuum magnetic field energy before a tokamak plasma formation and the MHD potential energy of an equilibrium tokamak plasma. Stationary direct current in a central solenoidal coil (DC_CS) can reduce δW_M, which means a reduction of the required heat energy for the tokamak plasma formation. The increase of the hole component ration in a toroidal plasma current distribution increases the toroidal plasma current and the stored thermal energy without increase of the plasma size. For tokamak plasmas with DC_CS = 100 A, δW_M has a local minimum with respect to the toroidal plasma current distribution. In this state, a perturbation of the toroidal plasma current is energetically inhibited.