Reactor-scale, 3D FRC simulations with WarpX's new hybrid-PIC solver

The field reversed configuration (FRC) has been extensively studied in the C-2W experiment [1] at TAE Technologies, where neutral beam injection, fueling, and edge biasing sustain advanced FRCs for many milliseconds. Stability simulations of these FRCs require fully kinetic ions due to their large fast ion populations. As a result, a kinetic-ion fluid-electron hybrid algorithm has recently been added [2] to the ECP particle-in-cell (PIC) code, WarpX [3]. The algorithm calculates the electric field using Ohm’s law without electron inertia and displacement current effects, and quasineutrality assumed. The solver models larger cell-sizes and time-steps compared to fully kinetic PIC codes, making reactor scale simulations possible. We present the application of WarpX’s hybrid solver to 3D, reactor scale, FRC simulations. Cylindrical domains are modeled on a 3D Cartesian grid using embedded boundaries (EBs) and cut-cell functionality in WarpX via AMReX. First, normal modes and dispersion relations of Alfvén waves in a cylindrical plasma with metallic walls are reproduced to verify the EB functionality. Next, n = 1 toroidal modes in FRCs are discussed, with a focus on the onset and growth of the tilt mode. Agreement with existing literature shows that WarpX’s hybrid solver is well-suited for FRC stability studies.

[1] H. Gota et al., Nucl. Fusion 61 106039 (2021).

[2] R. Groenewald et al., Sherwood Fusion Theory Conf. (2023).

[3] L. Fedeli et al., Int. Conf. for HPC, Networking, Storage and Analysis (2022).