Author: Jessica L. Li
Requested Type: Consider for Invited
Submitted: 2022-03-04 15:30:26
Co-authors: M.D.J.Cole, A.Reiman, M.Zarnstorff, C.S.Chang
Princeton Plasma Physics Lab
100 Stellarator Rd
Princeton, NJ 08540
Plasma transport in tokamaks and optimized stellarators is dominated by turbulence. It has been shown both experimentally and numerically that negative triangularity shaping in toroidal plasmas produces a stabilizing effect, likely due to the suppression ion-scale modes, which leads to lower levels of turbulent transport and thus improved confinement.
We investigate linear and nonlinear properties of ion-temperature-gradient (ITG) and trapped-electron-mode (TEM) instabilities through first-principles turbulence simulations using the global electromagnetic gyrokinetic code XGC. Microinstability growth rates are directly compared between simulations of equivalent positive- and negative-triangularity geometries of DIIID-D-like equilibria. Electrostatic adiabatic electron simulations show that linear adiabatic ITG can be modified by negative triangularity. Electromagnetic kinetic electron simulations at low beta find that linear kinetic ITG and TEM can both be stabilized by negative triangularity. The effects of various temperature and density profiles are explored, and temperature critical gradients are identified. We also examine the effectiveness and viability of this turbulence suppression mechanism when moving to reactor-relevant parameters such as high beta.