Optimum current density profile in a tokamak
Esipchuk Yu. V., Kadomtsev B. B.
A series of experiments on electron-cyclotron-resonance heating of the plasma in the T-10 tokamak shows that as the ratio of the plasma density to the current is increased, the radial profile of the current approaches a limiting profile. This limiting profile can be found from a simple variational principle corresponding to a minimum of the energy of the plasma and of the poloidal magnetic field at the given current.