Characterization of Turbulence and Transport in a Tokamak Power Plant

Starting from some general considerations, a simple model of transport in a tokamak power plant is proposed. The most important conclusion is that the plasma must be sufficiently well-coupled that there is significant ion thermal transport across the plasma core, even though alpha heating of the electrons will dominate over other heating processes. In addition, the lower collisionality of a future reactor relative to current devices means that neoclassical transport will be inherently weaker relative to turbulent processes in a reactor. When combined with the “fingerprint” paradigm [1], it then follows that tokamak reactor transport must be dominated by ion temperature gradient and/or kinetic ballooning mode turbulence across most of the confined plasma volume. In the context of core-edge integration, the key open questions are whether these instabilities will control transport across the entire confined plasma volume, and if not, how close to the edge does the transition to a different dominant transport process happen for reactor-relevant conditions? Implications for topics including density peaking and model validation in current facilities will be discussed.



[1] M. Kotschenreuther et al, Nuclear Fusion 59 096001 (2019)