Results from an extensive profile database analysis of JET density profiles in H-mode show that the density peaking factor ne0/ < ne > in JET H-modes increases as the effective collisionality drops from ∼1 at mid-radius to below 0.1 as expected for ITER. Density peaking is also strongly correlated with the Greenwald number NG, the particle outward flux Γ from the neutral beam source and Ti/Te. The correlations with li, q95, βN, ρ*, LTe, LTi, the toroidal Mach number and its shear are weak or insignificant. H- modes heated only by ICRH are, on average, only slightly less peaked than H-modes dominated by NBI, demonstrating that neutral beam fuelling can only explain a modest part (∼20%) of the peaking. Scaling expressions involving νeff, NG, RΓ/(neχ) and Ti/Te suggest that ne0/<ne > may exceed 1.5 in ITER, providing a boost of fusion power of more than 30% for fixed β and average density with respect to the usual assumption of a flat density profile.
Impact of fast ions on density peaking in JET: fluid and gyrokinetic modeling