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

Abstract

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. The 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. The 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 reduced by geometrical optimization. On the other hand, in LHD plasmas having relatively larger neoclassical transport than that in the above case, the peakedness of the density profiles decreased with decreasing collisionality. Density profiles in LHD plasmas tend to approach those in JT-60U, which are dominated by anomalous transport, as the contribution of neoclassical transport was reduced.