A possibility of `advanced tokamak' operation based on RF heating and current drive is studied using 1-D transport modelling for long pulse tokamaks such as Tore Supra. A current drive with lower hybrid and fast magnetosonic waves and strong electron heating with ion cyclotron waves are applied in this scenario. The self-consistent evolution of the energy, particles and current densities is simulated, starting from an ohmic plasma and arriving at a non-inductive steady state equilibrium. An estimation of the RF power required for the setting up of this equilibrium characterized by an improved confinement due to the building up of particle and energy internal transport barriers in the reversed magnetic shear configuration is presented. The maximum bootstrap current fraction attained in this scenario is about 50%. A limit on the bootstrap current fraction in plasmas with an L mode edge and improved core confinement produced due to the stabilizing effect of a low or negative magnetic shear is found. The conventional operational techniques with fixed plasma current or controlled plasma flux and non-inductive current are compared with the operation with the current profile control algorithm, and the advantages of current profile control are shown. The results presented are relevant to present tokamaks operating with RF heating and current drive and possibly to future tokamak projects aimed at advanced operation.
Overview of RF techniques in new confinement regimes with modified shear