Abstract Details
Abstracts
Author: Tess N Bernard
Requested Type: Consider for Invited
Submitted: 2026-03-10 09:14:08
Co-authors: F.D. Halpern, A.C.D. Hoffmann, M. Francisquez, A. Marinoni, G.W. Hammett, A. Hakim
Contact Info:
General Atomics
3550 General Atomics Ct
San Diego, California 92121
United States
Abstract Text:
We present full-f gyrokinetic simulations of DIII-D inner-wall-limited (IWL) discharges using the Gkeyll code to study how triangularity and neutral interactions influence profile formation and edge turbulence. Building on prior triangularity studies [1], this work incorporates an adaptive source model [2] and neutral collisions to better match experimental data. A semi-dynamic neutral fluid model is coupled to a gyrokinetic model for the plasma species, which is more computationally efficient than kinetic-to-gyrokinetic couplings [3], especially in realistic geometries. It captures essential effects of neutral interactions on the plasma, such as ionization sourcing and ion-neutral friction via charge exchange. These features provide a heat loss channel yielding realistic temperature values in the scrape-off layer with minimal user inputs.
Results demonstrate increased edge pressure values and reduced fluctuation levels and fluxes in negative triangularity (NT) simulations compared to positive triangularity (PT), consistent with experimental observations. A strong negative Reynolds stress is observed outside the last closed flux surface in NT. Applying the sheared spectral filament paradigm [4], we investigate the interplay of magnetic shear and ExB flow shear on turbulent eddies to quantify how turbulent transport is reduced in NT. These results highlight the critical role of plasma-neutral interactions in correctly predicting confinement properties and the importance of a global full-f gyrokinetic code for understanding the nonlinear effects of magnetic geometry on turbulent transport.
[1] Bernard 2024 PPCF 66(11), 115017
[2] Hoffmann 2026 NF, accepted (arXiv:2510.11874)
[3] Bernard 2022 PoP 29(5)
[4] Peret 2025 NF 65(5), 056043
This work was supported by the U.S. DOE contracts DE-AC02-09CH11466 and DE-FG02-04ER54742, as well as DOE’s Distinguished Scientist program and LDRD grants via DOE contract DE-AC02-09CH11466 for PPPL.
Characterization: 2.0
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