WarpX modeling of positive-ion neutral beam injection from acceleration grid to post-neutralization transport at Realta Fusion

Neutral beam injection (NBI) is an established heating method in magnetic confinement fusion. Accurate modeling of NBI systems requires simulating both the acceleration grids and neutral interactions through charge exchange and impact ionization. As part of the INFUSE collaboration, these capabilities were recently implemented in the particle-in-cell (PIC) code WarpX. This work presents a start-to-end NBI simulation including the extraction of beamlets through a plasma source, acceleration through biased grids, and neutralization in a gas target. In the absence of space charge effects, the steady-state neutralization fraction agrees well with theoretical predictions. Current efforts focus on how space charge affects the neutralization efficiency, which is crucial for NBI performance optimization.