Density profiles and turbulence in tokamak and helical plasmas

Tanaka, Kenji*; Takenaga, Hidenobu; Muraoka, Katsunori*; Michael, C.*; Vyacheslavov, L. N.*

In order to understand transport properties in toroidal plasmas, density profiles were compared in tokamak and helical plasmas. The density profiles tended to be peaked as the contribution of anomalous transport increases in JT-60U and LHD plasmas. In JT-60U ELMy H-mode plasmas and LHD plasmas at magnetic axis Rax=3.5 m, where the contribution of anomalous transport is large, a peaking factor of the density profile increased with decreasing normalized collisionality *. In LHD plasmas at Rax=3.6 m, where the contribution of anomalous transport is small, this factor decreased with decreasing * and the density profile became hollow one. In JT-60U ELMy H-mode plasmas, coherence increased as the density profile becomes peaked one. On the other hand, when the peaking factor of the density profile decreased with increasing heating power in LHD plasmas at Rax=3.6 m, anomalous diffusion increased due to increase in turbulence level and the direction of the convection velocity changed from inward to outward due to neoclassical transport.