The effect of divertor closure on the impurity stagnation point in detached L-mode discharges on DIII-D

M. G. Burke; F. Scotti; S. L. Allen; W. H. Meyer; A. Holm; M. Zhao; A. G. McLean; M. Fenstermacher; H. Q. Wang; R. Wilcox

doi:10.1016/j.nme.2025.101888

The effect of divertor closure on the impurity stagnation point in detached L-mode discharges on DIII-D

M. G. Burke
, F. Scotti
, S. L. Allen
, W. H. Meyer
, A. Holm
, M. Zhao
, A. G. McLean
, M. Fenstermacher
, H. Q. Wang
, R. Wilcox

Advanced Tokamak Physics

Research output: Contribution to journal › Article › peer-review

Abstract

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.

Original language	English
Article number	101888
Journal	Nuclear Materials and Energy
Volume	42
DOIs	https://doi.org/10.1016/j.nme.2025.101888
State	Published - Mar 2025

Funding

This material is based upon work supported by the U.S. Department of Energy, Office of Science , Office of Fusion Energy Sciences , using the DIII-D National Fusion Facility, a DOE Office of Science user facility, under Award(s) DE-FC02-04ER54698 , DE-AC52-07NA27344 , and DE-AC05-00OR22725 . This material is based upon work supported by the U.S. Department of Energy, Office of Science, Office of Fusion Energy Sciences, using the DIII-D National Fusion Facility, a DOE Office of Science user facility, under Award(s) DE-FC02-04ER54698, DE-AC52-07NA27344, and DE-AC05-00OR22725. This report was prepared as an account of work sponsored by an agency of the United States Government. Neither the United States Government nor any agency thereof, nor any of their employees, makes any warranty, express or implied, or assumes any legal liability or responsibility for the accuracy, completeness, or usefulness of any information, apparatus, product, or process disclosed, or represents that its use would not infringe privately owned rights. Reference herein to any specific commercial product, process, or service by trade name, trademark, manufacturer, or otherwise does not necessarily constitute or imply its endorsement, recommendation, or favoring by the United States Government or any agency thereof. The views and opinions of authors expressed herein do not necessarily state or reflect those of the United States Government or any agency thereof.

Keywords

Divertor
Tokamak

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10.1016/j.nme.2025.101888

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title = "The effect of divertor closure on the impurity stagnation point in detached L-mode discharges on DIII-D",

abstract = "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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doi = "10.1016/j.nme.2025.101888",

language = "English",

volume = "42",

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T1 - The effect of divertor closure on the impurity stagnation point in detached L-mode discharges on DIII-D

AU - Burke, M. G.

AU - Scotti, F.

AU - Allen, S. L.

AU - Meyer, W. H.

AU - Holm, A.

AU - Zhao, M.

AU - McLean, A. G.

AU - Fenstermacher, M.

AU - Wang, H. Q.

AU - Wilcox, R.

PY - 2025/3

Y1 - 2025/3

N2 - 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.

AB - 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.

KW - Divertor

KW - Tokamak

UR - https://www.scopus.com/pages/publications/85217686921

U2 - 10.1016/j.nme.2025.101888

DO - 10.1016/j.nme.2025.101888

M3 - Article

AN - SCOPUS:85217686921

SN - 2352-1791

VL - 42

JO - Nuclear Materials and Energy

JF - Nuclear Materials and Energy

M1 - 101888

ER -

The effect of divertor closure on the impurity stagnation point in detached L-mode discharges on DIII-D

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