Abstract Details
Abstracts
Author: Jessica L. Li
Requested Type: Poster
Submitted: 2024-04-12 22:07:51
Co-authors: C.S.Chang, A.Reiman, M.Zarnstorff
Contact Info:
Princton Plasma Physics Laboratory
100 Stellarator Rd
Princeton, NJ 08543
USA
Abstract Text:
Negative triangularity shaping has been demonstrated to improve heat confinement in tokamak plasmas both numerically and experimentally. This is theorized to be due to the stabilization of ion-scale microinstabilities such as ion-temperature-gradient (ITG) and trapped-electron-modes (TEM) leading to the suppression of turbulence, which is the dominant mechanism of transport. For this reason, there has been a resurgence of interest in modeling negative triangularity in recent years. We use the global electromagnetic gyrokinetic code XGC to model up-down symmetric positive and negative triangularity geometries of DIII-D-like equilibria at varying temperature and density profiles. We compare linear growth rates and critical gradients of these collisionless microinstabilities to study the triangularity-driven stabilization mechanism in different regimes, and find that in a kinetic-electron model, ITG and TEM are both stabilized by negative triangularity over a broad spectrum of mode numbers "n". However, this effect on ITG is not captured when using an adiabatic-electron model, even though it is conventionally thought that ITGs are driven by adiabatic electrons. In contrast, we identify no effect at low-n and a destabilizing effect of negative triangularity at high-n.
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