Scaling study for positive magnetic shear ELMy H-mode plasmas in JT-60U

Abstract

Scaling of the density peaking for positive magnetic shear ELMy H-mode plasmas in JT-60U has been developed. Although the density peaking generally depends on collisionality, a variation of the density peaking factor for the same collisionality exists, and the variation is different between plasmas with co-directed and ctr-directed toroidal rotation(co-VT plasmas and ctr-VT plasmas). The variation of the co-VT plasmas can be explained by particle source profile. As a result of scaling, the peaking factor of the co-VT plasmas depends on the particle source rate profile from neutral beams (NBs) as much as collisionality. The dataset of the ctr-VT plasmas has a larger variation of the peaking factor compared to that of the co-VT plasmas. The larger variation stems from that the peaking factor of the ctr-VT plasmas also depends on the normalized ion temperature gradient at the edge region. As a result of scaling, the normalized ion temperature gradient influences the peaking factor as much as or a little larger than collisionality. The parameter regime of the ctr-VT plasmas ranges from the trapped electron mode (TEM) to the ion temperature gradient mode (ITG mode). The plasmas with the positive correlation between the normalized density gradient and the normalized ion temperature gradient are dominated by the TEM. On the other hand, the plasmas with the negative correlation are dominated by the ITG mode.