ITER poloidal field system requirements for steady state reversed shear scenarios

Steady state operation is a major concern for tokamak reactors. It imposes strong requirements on confinement and MHD stability limits. The interest of current profile shaping to fulfill these requirements has been demonstrated by the enhanced plasma confinement observed in several tokamaks in the reversed shear (RS) configuration. In this paper the possibility to operate ITER in steady state at high fusion gain (Q ∼ 15) with about 100 MW of heating and current drive power is studied. A scenario is derived in which a steady state RS profile with a high bootstrap fraction is maintained with off-axis longer hybrid current drive (LHCD) and central fast wave current drive (FWCD). The main features of the 1-D code Astra which is used to model thermal transport and resistive diffusion of the plasma current density are described in the first part. The capability of the ITER poloidal field system to control the plasma during the whole discharge is checked with the 2D equilibrium code C res which is described in the second part. Finally in the third part the main steps of the scenario are presented along with comments on the requirements on the poloidal field system. (authors)