Based on a gyrokinetic analysis of and extrapolation from TCV discharges with large negative and positive triangularity δ, the potential of extreme in reducing turbulent transport is assessed. Linearly, both positive and negative δ can exert a stabilizing influence, with substantial sensitivity to the radial wavenumber kx. Nonlinear fluxes are reduced at extreme δ in a trapped-electron-mode regime, whereas low-amplitude ion-temperature-gradient turbulence is boosted by large negative δ. Focusing on the former case, nonlinear fluxes exceed quasilinear ones at negative δ, a trend that reverses as δ > 0. A change in saturation efficiency is the cause of these features: the zonal-flow residual is boosted at δ > 0, reducing fluxes compared with the linear drive as δ is increased, and a shift towards larger zonal-flow scales occurs with increasing δ due to finite-kx modes weakening with δ.
This paper explores how the triangularity of the magnetic field lines, a key parameter in fusion reactors, can significantly impact turbulent transport and reduce energy losses. The results show that both positive and negative triangularity can have a stabilizing effect, with the potential to boost fusion performance.