Comparisons of density profiles in JT-60U tokamak and LHD helical plasmas with low collisionality

Takenaga, Hidenobu; Tanaka, Kenji*; Muraoka, Katsunori*; Urano, Hajime; Oyama, Naoyuki; Kamada, Yutaka; Yokoyama, Masayuki*; Yamada, Hiroshi*; Tokuzawa, Tokihiko*; Yamada, Ichihiro*

In order to understand particle transport systematically in toroidal plasmas, electron density profiles were compared in JT-60U tokamak and LHD helical plasmas with low collisionality. Peakedness of density profiles increased with decreasing collisionality in ELMy H-mode plasmas of JT-60U, when the collisionality at half the minor radius was in the collisionless regime. Collisionality dependence of density profiles in LHD plasmas was similar to that in JT-60U plasmas in the same collisionality regime, when neoclassical transport was suppressed by geometrical optimization. On the other hand, in the LHD plasmas having relatively larger neoclassical transport than that in the above case, peakedness of density profiles decreased with decreasing collisionality. Neoclassical transport enhanced by the non-axisymmetric effect significantly affected density profiles with low collisionality in LHD plasmas. Density profiles in LHD plasmas tended to approach those in JT-60U, which are dominated by anomalous transport, as the contribution of neoclassical transport was reduced.