Density peaking in He plasmas

Angioni, C.*; Weisen, H.*; Zabolotsky, A.*; Ryter, F.*; Takenaga, Hidenobu

In order to contribute to the consideration that He plasmas will be used for the initial operation phase in ITER, density profiles are investigated in He plasmas on multi machines such as TCV, JET, AUG and JT-60U. He edge neutrals penetrate much less than H edge neutrals, because ratio CX to ionization rate coefficients is about one order of magnitude smaller in He. Despite of this, no significative difference in the density profiles is observed between pairs of similar D and He plasmas in TCV, JET, AUG, and JT-60U, in both L- and H-mode. This result provides further confirmation that neutral penetration (particle source/NBI fuelling) is not the main ingredient leading to peaked density profiles. AUG and JET He plasmas in H-mode have been included in the AUG/JET/C-Mod density peaking database. The subset of He plasmas exhibits the same collisionality dependence as the D plasmas, although there are no enough data to perform statistics though.