Possible mechanism responsible for observed impurity outward flow under radio frequency heating

Abstract

The effect of poloidal asymmetry of impurities on impurity transport driven by electrostatic turbulence in tokamak plasmas is analyzed. It is found that in the presence of in-out asymmetric impurity populations the zero-flux impurity density gradient (the so-called peaking factor) is significantly reduced. A sign change in the impurity flux may occur if the asymmetry is sufficiently large. This may be a contributing reason for the observed outward convection of impurities in the presence of radio frequency heating. The effect of in-out asymmetry is most significant in regions with low temperature gradients. In the trapped electron mode dominated case also an up-down asymmetry can lead to a sign change in the peaking factor from positive to negative. The effect of ion parallel compressibility on the peaking factor is significant, and leads to positive peaking factors in regions with high temperature gradients, even in the presence of in-out asymmetry.

19 pages, 14 figures

References in corpus (1)

• Impurity flows and plateau-regime poloidal density variation in a tokamak pedestal

Cited by in corpus (5)

• Impurity transport in trapped electron mode driven turbulence
• Turbulent transport of impurities and their effect on energy confinement
• Effects of the parallel acceleration on heavy impurity transport in turbulent tokamak plasmas
• Impurity transport in Alcator C-Mod in the presence of poloidal density variation induced by ion cyclotron resonance heating
• Radio frequency induced and neoclassical asymmetries and their effects on turbulent impurity transport in a tokamak