Design and physics basis for the upcoming DIII-D SAS-VW campaign to quantify tungsten leakage and transport in a new slot divertor geometry. (8th December 2021)

• Record Type: Journal Article
• Authors: Abrams, T; Sinclair, G; Nichols, J H; Unterberg, E A; Donovan, D C; Duran, J; Elder, J D; Glass, F; Grierson, B A; Guo, H Y; Hall, T; Ma, X; Maurizio, R; McLean, A G; Murphy, C; Nguyen, R; Rudakov, D L; Stangeby, P C; Thomas, D M; Zamperini, S A
• Is Part Of: Physica scripta. Volume 96:Number 12(2021)
• Publication Date: 2021-12-08
• Subjects: tungsten -- DIII-D -- divertors -- SOLPS -- DIVIMP -- spectroscopy -- tokamaks; Physics -- Periodicals; 530.05
• DOI: 10.1088/1402-4896/ac3c5f
• Languages: English
• ISSNs: 0031-8949

Abstract

Abstract: A set of experiments are planned to exploit the high SOL collisionality enabled by a tightly baffled slot divertor geometry to suppress tungsten leakage in DIII-D. A toroidal row of graphite tiles from the Small Angle Slot (SAS) divertor is being coated with 10–15 μ m of tungsten. New spectroscopic viewing chords with in-vacuo optics will measure the W gross erosion source from the divertor surface with high spatial and temporal resolution. In parallel, the bottom of the SAS divertor is changed from a flat to a 'V' shape. New SOLPS-ITER/DIVIMP simulations conducted with drifts using the planned 'V' shape predict a substantial reduction in W sourcing and SOL accumulation in either B × ∇B direction relative to either the old SAS divertor shape or the open, lower divertor. Dedicated studies are planned to carefully characterize the level of W sourcing, leakage, and scrape-off-layer (SOL) accumulation in DIII-D over a wide range of plasma scenarios. Various actuators will be assessed for their efficacy in further reducing high-Z impurity sources and leakage from the slot divertor geometry. This coupled code-experiment validation effort will be used to stress-test physics models and build confidence in extrapolations to advanced, high-Z divertor geometries for next-step devices.