Stationary magnetic entropy tokamak states and experimental observations

The assumption that the tokamak magnetic configuration at equilibrium is associated with the stationary magnetic entropy and with minimum plasma thermal energy leads to the prediction of definite profiles for the induced current density and for the pressure. These profiles should characterize the states spontaneously assumed by the tokamak under normal conditions (to be defined in the text). The theoretical results are compared with the observations collected from different tokamaks, plasma regimes and heating methods, taking into account the possible existence of non-inductive currents. The comparison allows the identification of the limits of validity of the model and confirms the robustness, within these limits, of the magnetic entropy concept for the description of the 'privileged' tokamak states.