Peaked Density Profiles in Low Collisionality H-modes in JET, ASDEX Upgrade and TCV

Results from an extensive database analysis of JET and AUG density profiles in H-mode, show that the density peaking factor ne0/·neÒ increases to above 1.5 as the effective collisionality drops to values close to those expected for ITER. On any single device density peaking is also strongly correlated with the Greenwald number NG and the particle outward flux G from the neutral beam source, when applicable. Fully RF-heated H-modes in JET and TCV show that neutral beam fuelling is not the dominant contributor to density peaking. Multiple regression analyses are performed which show that in the combined database, collisionality is the most relevant parameter. Scalings for density peaking are proposed and implications for ITER performance are discussed.
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