Hannover 2016 – scientific programme

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P: Fachverband Plasmaphysik

P 21: Magnetic Confinement II

P 21.2: Invited Talk

Thursday, March 3, 2016, 11:30–12:00, b302

Energy and Particle Core Transport in Tokamaks and Stellarators compared — •Marc Beurskens, Clemente Angioni, Craig Beidler, Andreas Dinklage, Golo Fuchert, Matthias Hirsch, Thomas Puetterich, and Robert Wolf — Max-Planck-Institut für Plasmaphysik, 17491 Greifswald/85748 Garching, Germany

The paper discusses expectations for core transport in the Wendelstein 7-X stellarator (W7-X) and presents a comparison to tokamaks. In tokamaks, the neoclassical trapped-particle-driven losses are small and turbulence dominates the energy and particle transport. At reactor relevant low collisionality, the heat transport is limited by ion temperature gradient limited turbulence, clamping the temperature gradient. The particle transport is set by an anomalous inward pinch, yielding peaked profiles. A strong edge pedestal adds to the good confinement properties. In traditional stellarators the 3D geometry cause increased trapped orbit losses. At reactor relevant low collisionality and high temperatures, these neoclassical losses would be well above the turbulent transport losses. The W7-X design minimizes neoclassical losses and turbulent transport can become dominant. Moreover, the separation of regions of bad curvature and that of trapped particle orbits in W7-X may have favourable implications on the turbulent electron heat transport. The neoclassical particle thermodiffusion is outward. Without core particle sources the density profile is flat or even hollow. The presence of a turbulence driven inward anomalous particle pinch in W7-X (like in tokamaks) is an open topic of research.