Density peaking in low collisionality ELMy H-mode in JET

Low collisionality, low particle source, ELMy H-modes (type-III) with sawteeth are produced in JET in order to address the question of density profile evolution in the reference q ₉₅ = 3 ITER scenario. The paper focuses on particle transport in the core zone around the mid-radius. The pedestal region including ELMs and the region affected by sawteeth are not considered. By replacing a significant part of the neutral beam heating by RF power the beam particle flux at mid-radius has been reduced to γ _Beam/n _c = 0.07m s ^-1. The additional flux due to wall neutrals is estimated as γ _wall/n _c ≤ 0.12 m s ^-1. Density profiles are found to be modestly peaked under these conditions with a relative density difference of δn/〈n〉 = 0.23 across the zone not affected by sawteeth and ELMs. In a region around the mid-radius the ratio of effective particle diffusivity to electron thermal diffusivity is found to be D _e,eff/χ _e ≈ 0.2, which might indicate an anomalous pinch provided the particle diffusivity D _e is sufficiently large. The measured values of D _e,eff/χ _e are at the lower end of the range used in ITER models.