Study of tungsten transport and redeposition during the DIII-D Metal Rings Campaign using the impurity tracing code GITRm

Experiments have been conducted at DIII-D to understand W impurity transport using toroidally symmetric metal rings located in the lower divertor region of the tokamak. Experimental measurements of W gross erosion and redeposition in the outboard lower divertor and mid-plane collector probes indicate that the long-range transport of W impurities depends significantly on 3D effects induced by poloidal and radial E x B drifts [1]. Here we develop and apply the unstructured mesh-based, and accelerator/GPU-enabled, Global Impurity Tracing code, GITRm [2], to track particles through the entire DIII-D vessel, within the trace-impurity assumption. GITRm has been used to study the erosion, long-range transport, and redeposition of W in the lower divertor and mid-plane collector probes, and benchmarked to previous studies. Background plasmas were extended to the wall and have been previously used to match radial profiles of tungsten deposition with far-SOL collector probes. These benchmarked results demonstrate the utility of GITRm compared to other impurity tracing codes, and highlight the need for 3-dimensional modeling of impurity transport in the scrape-off-layer.



[1] Zamperini et al., Nuclear Materials and Energy 25 (2020) 100811

[2] Shephard et al. A 3D Unstructured Mesh-based Global Impurity Transport Code [abstract]. In: 63rd Annual Meeting of the APS Division of Plasma Physics, Session NM09; 2021 Nov. 13, Pittsburgh, PA. NM09.00005.