Plasma size scaling of avalanche-like heat transport in tokamaks

Jolliet, S.; Idomura, Yasuhiro   

The influence of plasma size on global Ion Temperature Gradient turbulence is studied with the full- Eulerian code GT5D. Plasma sizes from to are studied by scaling the minor radius and the input power. For the first time, worse-than-Bohm scaling is observed in experimentally realistic conditions. Global effects are investigated by looking at the force balance relation and the avalanches dynamics. It is found that the parallel momentum and radial electric field profiles are coupled. A low shearing rate region is induced in the large plasma size simulation and enhances heat transport. In this region, the dynamics of avalanches is altered. GT5D simulations therefore highlight avalanches as a non-local mechanism for broken gyro-Bohm scaling and point out the importance of the yet unknown plasma size effects on momentum transport.