Predicting tungsten erosion and leakage properties for the new V-shaped small angle slot divertor in DIII-D. (1st October 2022)

• Record Type: Journal Article
• Authors: Sinclair, G.; Maurizio, R.; Ma, X.; Abrams, T.; Elder, J.D.; Guo, H.Y.; Thomas, D.M.; Leonard, A.W.
• Is Part Of: Nuclear fusion. Volume 62:Number 10(2022)
• Publication Date: 2022-10-01
• Subjects: plasma-material interactions -- SOLPS-ITER -- divertor closure -- tungsten -- erosion -- DIII-D; Nuclear fusion -- Periodicals; 621.48405
• DOI: 10.1088/1741-4326/ac8b95
• Languages: English
• ISSNs: 0029-5515

Abstract

Abstract: Impurity transport modeling of the new tungsten (W)-coated, V-shaped small angle slot (SAS) divertor in the DIII-D tokamak was conducted using the SOLPS-ITER plasma edge code package and the DIVIMP impurity tracking code. The inboard baffle of the current SAS divertor will be shifted closer to the outboard baffle, creating a V-corner at the slot vertex. In addition, the outboard baffle will be coated with 10–15 μ m of W for experiments studying high-Z sourcing and leakage in a closed divertor. Modeling of the 'SAS-VW' divertor predicts that these changes to the inner baffle will reduce W gross erosion by 40× relative to the existing SAS divertor when the outer strike point (OSP) is at the V-corner and the ion B × ∇ B drift is towards the divertor, driven primarily by significant cooling near the slot vertex. Most W erosion in SAS-VW is expected to occur near the slot entrance, which may pose a higher risk to core contamination than W eroded deeper in the slot. Adding a new sheath-based prompt redeposition model outlined in Guterl et al (2021 Nucl. Mater. Energy 27 100948) increases the sensitivity of redeposition estimates to near-target plasma conditions and may provide more accurate predictions of net erosion. Moving the OSP outboard from the slot vertex ∼4 cm onto the W-coated region yields a 40× increase in the gross erosion rate and a 50% decrease in the core leakage fraction. Thus slight variations in strike point location may counteract the potential benefits of the tightly-baffled V slot on minimizing erosion. This impurity transport modeling provides useful guidance for future experiments on the SAS-VW divertor focused on high-Z erosion/redeposition, scrape-off layer transport, and core leakage.