Publication Date:
2014-12-20
Description:
Modulation charge eXchange recombination spectroscopy measurements with high spatial and temporal resolution have made the evaluation of the toroidal plasma flow of fully stripped carbon impurity ions ( V ϕ C 6 + ) in the JT-60U tokamak peripheral region (including, in particular, the separatrix) possible with a better signal-to-noise ratio. By comparing co- and counter-neutral beam injection discharges experimentally, we have identified the boundary condition of V ϕ C 6 + and radial electric field shear ( ∇ E r ) imposed at the separatrix in high confinement (H-mode) plasmas with edge localized modes (ELMs). The V ϕ C 6 + value at the separatrix is not fixed at zero but varies with the momentum input direction. On the other hand, the ∇ E r value is nearly zero (or very weakly positive) at the separatrix. Furthermore, the edge localized mode perturbation does not appear to affect both V ϕ C 6 + and ∇ E r values at the separatrix as strongly as that in the pedestal region. The above experimental findings based on the precise edge measurements have been used to validate a theoretical model and develop a new empirical model. A better understanding of the physical process in the edge transport barrier (ETB) formation due to the sheared E r formation is also discussed.
Print ISSN:
1070-664X
Electronic ISSN:
1089-7674
Topics:
Physics
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