Simulations of ITER with combined effects of internal and edge transport barriers

Predictive simulations of ITER with the presence of both an edge transport barrier (ETB) and an internal transport barrier (ITB) are carried out using the BALDUR integrated predictive modelling code. In these simulations, the boundary is taken at the top of the pedestal, where the pedestal values are described using theory-based pedestal models. These pedestal temperature models are based on three different pedestal width scalings: magnetic and flow shear stabilization (Δ ∝ ρis2), flow shear stabilization () and normalized poloidal pressure (). The pedestal width scalings are combined with a pedestal pressure gradient scaling based on the ballooning mode limit to predict the pedestal temperature. A version of the semi-empirical Mixed Bohm/gyroBohm (Mixed B/gB) core transport model that includes ITB effects is used to compute the evolution of plasma profiles. In this model, the anomalous transport in the core is stabilized by the influence of Er × B flow shear and magnetic shear, which results in the formation of ITB. The combination of the Mixed B/gB core transport model with ITB effects, together with the pedestal model, is used to simulate the time evolution of plasma current, temperature, and density profiles for ITER standard type I ELMy H-mode discharges. It is found that ITER fusion performance using the BALDUR code with Mixed B/gB transport model without the presence of ITB is quite pessimistic (Fusion Q ∼ 3). The presence of ITB is crucial and can result in a significant improvement, which is needed for achieving a target Fusion Q of 10. The improvement due to the presence of ITB is almost the same for all simulations with those three pedestal temperature models. This is caused by the predicted pedestal temperature from each pedestal temperature model varying just slightly. The presence of ITB has a strong impact on both temperature profiles, especially near the centre of the plasma, but has a small impact on electron, deuterium, tritium and carbon density profiles, except the helium density profile. The formation of ITB does not impact on the pedestal. It is also found that during a sawtooth crash, the temperature profiles drop significantly, but there is a small change in the density profiles. However, the sawtooth oscillation has no impact on the pedestal. When the auxiliary heating power is turned off, it is found that significant fusion power is sustained.