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The effect of divertor closure on the impurity stagnation point in detached L-mode discharges on DIII-D
This paper presents experimental measurements of the location of the impurity flow stagnation point in the scrape-off-layer (SOL) of a tokamak plasma. Coherence imaging of carbon-2+ emission (465 nm) is used to track the main-chamber impurity velocity of DIII-D L-mode plasmas with B×∇B out of the divertor. The C2+ flow stagnates near the top or crown of the plasma when an open divertor (no baffling) is used. In contrast, with matched conditions and using a divertor with baffling, the C2+ flow stagnates near the outer divertor leg (X-point). The C2+ poloidal emission is hollow, peaking near the divertor legs, in the open configuration. In contrast, in the closed configuration, the C2+ emission is flat through most of the main-chamber SOL. Changing divertor dissipation from attached to detached conditions had only a minor effect on the main-chamber midplane impurity velocity. Numerical simulations using the multi-fluid edge transport code UEDGE including cross-field drifts show qualitative agreement with the open divertor experimental result.
The effect of divertor closure on the impurity stagnation point in detached L-mode discharges on DIII-D
This paper presents experimental measurements of the location of the impurity flow stagnation point in the scrape-off-layer (SOL) of a tokamak plasma. Coherence imaging of carbon-2+ emission (465 nm) is used to track the main-chamber impurity velocity of DIII-D L-mode plasmas with B×∇B out of the divertor. The C2+ flow stagnates near the top or crown of the plasma when an open divertor (no baffling) is used. In contrast, with matched conditions and using a divertor with baffling, the C2+ flow stagnates near the outer divertor leg (X-point). The C2+ poloidal emission is hollow, peaking near the divertor legs, in the open configuration. In contrast, in the closed configuration, the C2+ emission is flat through most of the main-chamber SOL. Changing divertor dissipation from attached to detached conditions had only a minor effect on the main-chamber midplane impurity velocity. Numerical simulations using the multi-fluid edge transport code UEDGE including cross-field drifts show qualitative agreement with the open divertor experimental result.
The effect of divertor closure on the impurity stagnation point in detached L-mode discharges on DIII-D
M.G. Burke (author) / F. Scotti (author) / S.L. Allen (author) / W.H. Meyer (author) / A. Holm (author) / M. Zhao (author) / A.G. McLean (author) / M. Fenstermacher (author) / H.Q. Wang (author) / R. Wilcox (author)
2025
Article (Journal)
Electronic Resource
Unknown
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