How far 3D shaping can reduce turbulent transport
In plain words
Optimized stellarators have nearly eliminated collisional heat loss, so turbulence now dominates. How much turbulence can be reduced just by choosing the magnetic shape is unknown.
Precise statement
In W7-X, ion-temperature-gradient turbulence clamps the ion temperature near 1.5 keV in electron-heated plasmas unless the density profile is peaked. Determine the minimum nonlinear gyrokinetic ion heat flux at fixed normalized gradients achievable by 3D shaping, using nonlinear gyrokinetics inside the optimization loop, and validate the predicted reduction experimentally. An answer is the attainable reduction factor relative to W7-X at fixed gradients.
What would settle it
An optimized configuration whose predicted turbulence reduction is confirmed in a new or modified stellarator experiment.