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Neoclassical flows in deuterium-helium plasma density pedestals

Stefan Buller (Institutionen för fysik, Subatomär fysik och plasmafysik (Chalmers)) ; István Pusztai (Institutionen för fysik, Subatomär fysik och plasmafysik (Chalmers)) ; Sarah Newton (Institutionen för fysik, Subatomär fysik och plasmafysik (Chalmers)) ; John Omotani (Institutionen för fysik, Subatomär fysik och plasmafysik (Chalmers))
(2016)
[Preprint]

In tokamak transport barriers, the radial scale of profile variations can be comparable to a typical ion orbit width, which makes the coupling of the distribution function across flux surfaces important in the collisional dynamics. We use the radially global steady-state neoclassical δf code Perfect to calculate poloidal and toroidal flows, and radial fluxes, in the pedestal. In particular, we have studied the changes in these quantities as the plasma composition is changed from a deuterium bulk species with a helium impurity to a helium bulk with a deuterium impurity, under specific profile similarity assumptions. The poloidally resolved radial fluxes are not divergence-free in isolation in the presence of sharp radial profile variations, which leads to the appearance of poloidal return-flows. These flows exhibit a complex radial-poloidal structure that extends several orbit widths into the core and is sensitive to abrupt radial changes in the ion temperature gradient. We find that a sizable neoclassical toroidal angular momentum transport can arise in the radially global theory, in contrast to the local.

Nyckelord: Neoclassical transport fusion tokamak helium deuterium flows



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Denna post skapades 2016-11-29.
CPL Pubid: 245720