The simulation of the advanced non-inductive operating regimes was carried out by means of 1.5D predictive transport code ASTRA. The goal of the study was to investigate the steady-state operations in ITER under constrain of ITER heating and current drive systems and different assumptions regarding energy confinement including transport barriers in reversed-shear configurations (q' < 0).

Neutral Beam (NB) alone or in combination with the Electron Cyclotron Resonance (ECR) waves were employed to heat the plasma and sustain the plasma current. NB absorption, power deposition in the plasma and current generation were simulated taking into account ITER beam and plasma geometry and under limitation of total NB power P_NB ² 50 MW. Simulation of the ECR heating and CD was performed with the help of a simplified model derived from and benchmarked with the more elaborate Fokker-Plank calculations (code OGRAY). The ECR power was also limited by 50 MW, however, to make a wider scan it was extended to 100 MW in some of the runs.

The first set of calculation was done for the standard H-mode regimes. In this case the local transport coefficients for the thermal conductivity were normalized to obtain the energy confinement time given by the global H-mode scaling. Plasma density was assumed to be flat and the helium ash content was calculated self consistently under assumption t_He^*/t_E = 5-7. It was found that the steady-state operation with exclusively non-inductive current drive can be achieved even at the standard confinement (ELMy H-mode) or at slightly improved confinement with enhancement factor H = 1.5. The plasma currents of 10 to 15 MA can be generated by NB alone or in a combination with ECR waves. However, in the H-mode the steady state regimes can be achieved only at a low plasma density and hence have low Q values (Q = P_fus/P_aux ) which hardly reaches the design goal Q=5. At the available total power of 100 MW the H-mode energy confinement is not sufficient to achieve high density regimes with the high fraction of the bootstrap current (IBS/I_p = 70-80%).

Regimes with a thermal barrier look much more attractive for SS operation in ITER. The regimes were modeled by reducing ion heat transport and particle diffusion (including He diffusion) to the neoclassical value in the region with negative shear, q' < 0. Inverse shear was achieved in the simulations by off-axis ECR current drive. It was found that after creation of the transport barrier ion temperature significantly grows which give rise to the fusion power and facilitate transition to the regimes with high bootstrap current. In spite of the transport barrier, only a small increase in the central He concentration was observed in the simulations. Non-inductive current of 10 to 14 MA can be maintained by a combination of ECR and NB powers of 50 and 10 MW correspondingly. Bootstrap fraction reaches 75% at higher plasma densities. The thermonuclear gain up to Q = 30 has been demonstrated in the simulations.