A High-order piecewise field-aligned triangular finite element method for electromagnetic gyrokinetic particle simulations of tokamak plasmas with open field lines
Zhixin Lu, Guo Meng, Eric Sonnendrücker, Roman Hatzky, Giorgio Daneri, Gengxian Li, Peiyou Jiang, Klaus Reuter, Matthias Hoelzl
Abstract
Abstract A high-order piecewise field-aligned triangular finite element method is developed and implemented for global electromagnetic gyrokinetic particle-in-cell simulations of tokamak plasmas with open field lines. The approach combines locally field-aligned finite element basis functions with unstructured C 1 triangular meshes in cylindrical coordinates, enabling whole-volume simulations with substantially reduced computational effort, while avoiding the grid distortion associated with globally field-aligned coordinates and the associated singularity at the separatrix of diverted plasmas. The formulation is compatible with both δ f and full- f models and employs mixed-variable representations, along with a generalized pullback scheme, to control numerical cancellation in electromagnetic simulations. The method is implemented in the TRIMEG-C1 code and demonstrated using linear and nonlinear electromagnetic simulations of the Tokamak á configuration variable-X21 configuration. The results indicate that the approach accurately captures the key features of electromagnetic ion-temperature-gradient and kinetic ballooning mode physics, including the separatrix regions in the simulation, thereby providing a robust framework for whole-volume electromagnetic gyrokinetic simulations in realistic tokamak geometries.
BibTeX
@article{Lu_2026,
title={A High-order piecewise field-aligned triangular finite element method for electromagnetic gyrokinetic particle simulations of tokamak plasmas with open field lines},
volume={68},
ISSN={1361-6587},
url={http://dx.doi.org/10.1088/1361-6587/ae6ace},
DOI={10.1088/1361-6587/ae6ace},
number={5},
journal={Plasma Physics and Controlled Fusion},
publisher={IOP Publishing},
author={Lu, Zhixin and Meng, Guo and Sonnendrücker, Eric and Hatzky, Roman and Daneri, Giorgio and Li, Gengxian and Jiang, Peiyou and Reuter, Klaus and Hoelzl, Matthias},
year={2026},
month=May,
pages={055027} }