WallDYN modeling of tungsten migration in the DIII-D divertor*

The DIVIMP-WallDYN code has been applied to DIII-D for the first time, self-consistently combining impurity production and transport models to dynamically model tungsten (W) re-deposition and re-erosion during the 2016 Metal Rings Campaign. Modeling of the transport of strike point-sourced W to other locations in the divertor during DIII-D L-mode discharges is presented. Collector probes in DIII-D, DiMES and MiMES, have been used to measure W deposition across a range of plasma conditions. However, modeling is needed to link measured W sourcing to measured deposition, and benchmarking with experimental observations from collector probes and W-I spectroscopy can be used as figures of merit for the model. While many aspects of the model are constrained by diagnostics, some key parameters remain ill-constrained, and model sensitivity to these parameters (plasma ion temperature, radial and poloidal electric fields, and mixed-material sputtering) is examined. It is found that both long-range single-step transport and short-range transport due to multiple re-erosion steps are important contributors to W transport in DIII-D.