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 di...
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| Main Authors: | , , , , , , , , , |
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| Format: | Article |
| Language: | English |
| Published: |
Elsevier
2025-03-01
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| Series: | Nuclear Materials and Energy |
| Subjects: | |
| Online Access: | http://www.sciencedirect.com/science/article/pii/S2352179125000286 |
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| Summary: | 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. |
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| ISSN: | 2352-1791 |