Integrated modeling of solid boron injection for real-time coating of tokamak plasmas-facing components*

New integrated modeling of real-time wall conditioning via boron (B) powder injection in the DIII-D tokamak shows qualitative agreement with the experimentally observed formation of B-rich coatings near the outer strike point, where B growth rates of ~0.9 nm/s were measured. The results indicate a more uniform toroidal and balanced poloidal distribution of coatings, accounting for the observed B deposition level on the outer divertor.

The Dust Injection Simulator (DIS) was combined with EMC3-EIRENE to model the B powder particle transport and ablation, revealing B flux distribution asymmetries similar to single-point injection modeling [1]. However, these models do not account for erosion and re-deposition, failing to replicate the observed B deposition on the outer divertor target.

Therefore, erosion, migration, and re-deposition of B were modeled by integrating EMC3-EIRENE and DIS with WallDYN3D [2]. This approach, including the mixed-material dynamics at the surface, more realistically replicates real-time wall coating with B powders, achieving B surface concentrations of 0.4 close to those observed in experimental B-C layers.

This integrated modeling approach provides a basis for analyzing real-time coatings and conditioning techniques in advanced tokamak scenarios and predictive studies for solid boron injection in ITER.

[1] F. Effenberg et al 2021 Nucl. Mater. and Energy 26 100900

[2] K. Schmid et al 2020 Nucl. Mater. Energy 25 100821