Distinct Turbulence Saturation Regimes in Stellarators

G. G. Plunk, P. Xanthopoulos, and P. Helander

Phys. Rev. Lett. 118, 105002 – Published 8 March 2017; Erratum Phys. Rev. Lett. 119, 139901 (2017)

Abstract

In the complex 3D magnetic fields of stellarators, ion-temperature-gradient turbulence is shown to have two distinct saturation regimes, as revealed by petascale numerical simulations and explained by a simple turbulence theory. The first regime is marked by strong zonal flows and matches previous observations in tokamaks. The newly observed second regime, in contrast, exhibits small-scale quasi-two-dimensional turbulence, negligible zonal flows, and, surprisingly, a weaker heat flux scaling. Our findings suggest that key details of the magnetic geometry control turbulence in stellarators.