Tungsten erosion during L-mode discharges in the DIII-D SAS-VW divertor

G. Sinclair; T. Abrams; M. S. Parsons; S. H. Messer; J. Mateja; S. A. Zamperini; D. M. Thomas; J. D. Elder; R. Maurizio; T. Odstrcil; R. S. Wilcox; J. L. Herfindal; D. D. Truong; J. G. Watkins; A. G. McLean; D. L. Rudakov; J. Ren; D. Donovan

doi:10.1016/j.nme.2025.101884

Tungsten erosion during L-mode discharges in the DIII-D SAS-VW divertor

G. Sinclair, T. Abrams, M. S. Parsons, S. H. Messer, J. Mateja, S. A. Zamperini, D. M. Thomas, J. D. Elder, R. Maurizio, T. Odstrcil, R. S. Wilcox, J. L. Herfindal, D. D. Truong, J. G. Watkins, A. G. McLean, D. L. Rudakov, J. Ren, D. Donovan

Advanced Tokamak Physics

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

Abstract

A series of L-mode plasma discharges was performed in the DIII-D tokamak to assess the impact of outer strike point (OSP) position and toroidal magnetic field direction on erosion and core contamination potential of the recently-installed, tungsten-coated Small Angle Slot (SAS-VW) divertor. In one discharge, in-slot emission spectroscopy measured an < 48 % increase in the W gross erosion rate when the OSP was moved 3 cm outwards, away from the V-shaped vertex of the slot divertor. However, the effective W yield (erosion rate divided by the incident D flux) was, overall, insensitive to changes in OSP location. Consistently low estimates of the effective W yield based on measurements taken a few cm outwards from the vertex suggest potentially significant C surface contamination. No W emission signal was detected when orienting the toroidal magnetic field such that the ion B×∇B drift direction is pointed away from the X-point. However, measurements of W content in the plasma core for both toroidal magnetic field directions suggest the presence of additional, unmeasured sources of erosion. The difference in the measured core W density with OSP position is much greater than the difference in the measured erosion rates, which may suggest that the leakage of eroded impurities out of the divertor is governed primarily through the parallel ion temperature gradient and friction forces.

Original language	English
Article number	101884
Journal	Nuclear Materials and Energy
Volume	42
DOIs	https://doi.org/10.1016/j.nme.2025.101884
State	Published - Mar 2025

Funding

This work was supported by the U.S. Department of Energy under Grants U.S. DE-FC02-04ER54698, DE-SC0020093, DE-SC0019256, DE-SC0023378, DE-AC05-00OR22725, DE-NA0003525, and DE-AC52-07NA27344. Authors would like to thank Al Hyatt, Ivo Carvalho, and Tony Leonard for their assistance executing this experiment as physics operators and beam programmers and providing useful input that ensured its success. Authors would also like to thank Huiqian Wang for their assistance in analyzing Langmuir probe data. Authors would also like to thank Gilson Ronchi for their assistance in analyzing filterscope data. Authors would also like to thank Jacob Nichols for providing valuable insight on the interpretation of erosion measurements. DIII-D data shown in this paper can be obtained in digital format by following the links at https://fusion.gat.com/global/diii-d/dmp. 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. This work was supported by the U.S. Department of Energy under Grants U.S. DE-FC02-04ER54698 , DE-SC0020093 , DE-SC0019256 , DE-SC0023378 , DE-AC05-00OR22725 , DE-NA0003525 , and DE-AC52-07NA27344 . Authors would like to thank Al Hyatt, Ivo Carvalho, and Tony Leonard for their assistance executing this experiment as physics operators and beam programmers and providing useful input that ensured its success. Authors would also like to thank Huiqian Wang for their assistance in analyzing Langmuir probe data. Authors would also like to thank Gilson Ronchi for their assistance in analyzing filterscope data. Authors would also like to thank Jacob Nichols for providing valuable insight on the interpretation of erosion measurements. DIII-D data shown in this paper can be obtained in digital format by following the links at https://fusion.gat.com/global/diii-d/dmp .

Keywords

Divertor
Optical spectroscopy
Plasma-material interactions
Tokamaks
Tungsten

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10.1016/j.nme.2025.101884

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Sinclair, G., Abrams, T., Parsons, M. S., Messer, S. H., Mateja, J., Zamperini, S. A., Thomas, D. M., Elder, J. D., Maurizio, R., Odstrcil, T., Wilcox, R. S., Herfindal, J. L., Truong, D. D., Watkins, J. G., McLean, A. G., Rudakov, D. L., Ren, J., & Donovan, D. (2025). Tungsten erosion during L-mode discharges in the DIII-D SAS-VW divertor. Nuclear Materials and Energy, 42, Article 101884. https://doi.org/10.1016/j.nme.2025.101884

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title = "Tungsten erosion during L-mode discharges in the DIII-D SAS-VW divertor",

abstract = "A series of L-mode plasma discharges was performed in the DIII-D tokamak to assess the impact of outer strike point (OSP) position and toroidal magnetic field direction on erosion and core contamination potential of the recently-installed, tungsten-coated Small Angle Slot (SAS-VW) divertor. In one discharge, in-slot emission spectroscopy measured an < 48 \% increase in the W gross erosion rate when the OSP was moved 3 cm outwards, away from the V-shaped vertex of the slot divertor. However, the effective W yield (erosion rate divided by the incident D flux) was, overall, insensitive to changes in OSP location. Consistently low estimates of the effective W yield based on measurements taken a few cm outwards from the vertex suggest potentially significant C surface contamination. No W emission signal was detected when orienting the toroidal magnetic field such that the ion B×∇B drift direction is pointed away from the X-point. However, measurements of W content in the plasma core for both toroidal magnetic field directions suggest the presence of additional, unmeasured sources of erosion. The difference in the measured core W density with OSP position is much greater than the difference in the measured erosion rates, which may suggest that the leakage of eroded impurities out of the divertor is governed primarily through the parallel ion temperature gradient and friction forces.",

keywords = "Divertor, Optical spectroscopy, Plasma-material interactions, Tokamaks, Tungsten",

author = "G. Sinclair and T. Abrams and Parsons, \{M. S.\} and Messer, \{S. H.\} and J. Mateja and Zamperini, \{S. A.\} and Thomas, \{D. M.\} and Elder, \{J. D.\} and R. Maurizio and T. Odstrcil and Wilcox, \{R. S.\} and Herfindal, \{J. L.\} and Truong, \{D. D.\} and Watkins, \{J. G.\} and McLean, \{A. G.\} and Rudakov, \{D. L.\} and J. Ren and D. Donovan",

note = "Publisher Copyright: {\textcopyright} 2025 The Authors",

year = "2025",

month = mar,

doi = "10.1016/j.nme.2025.101884",

language = "English",

volume = "42",

journal = "Nuclear Materials and Energy",

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Sinclair, G, Abrams, T, Parsons, MS, Messer, SH, Mateja, J, Zamperini, SA, Thomas, DM, Elder, JD, Maurizio, R, Odstrcil, T, Wilcox, RS , Herfindal, JL, Truong, DD, Watkins, JG, McLean, AG, Rudakov, DL, Ren, J & Donovan, D 2025, 'Tungsten erosion during L-mode discharges in the DIII-D SAS-VW divertor', Nuclear Materials and Energy, vol. 42, 101884. https://doi.org/10.1016/j.nme.2025.101884

TY - JOUR

T1 - Tungsten erosion during L-mode discharges in the DIII-D SAS-VW divertor

AU - Sinclair, G.

AU - Abrams, T.

AU - Parsons, M. S.

AU - Messer, S. H.

AU - Mateja, J.

AU - Zamperini, S. A.

AU - Thomas, D. M.

AU - Elder, J. D.

AU - Maurizio, R.

AU - Odstrcil, T.

AU - Wilcox, R. S.

AU - Herfindal, J. L.

AU - Truong, D. D.

AU - Watkins, J. G.

AU - McLean, A. G.

AU - Rudakov, D. L.

AU - Ren, J.

AU - Donovan, D.

PY - 2025/3

Y1 - 2025/3

N2 - A series of L-mode plasma discharges was performed in the DIII-D tokamak to assess the impact of outer strike point (OSP) position and toroidal magnetic field direction on erosion and core contamination potential of the recently-installed, tungsten-coated Small Angle Slot (SAS-VW) divertor. In one discharge, in-slot emission spectroscopy measured an < 48 % increase in the W gross erosion rate when the OSP was moved 3 cm outwards, away from the V-shaped vertex of the slot divertor. However, the effective W yield (erosion rate divided by the incident D flux) was, overall, insensitive to changes in OSP location. Consistently low estimates of the effective W yield based on measurements taken a few cm outwards from the vertex suggest potentially significant C surface contamination. No W emission signal was detected when orienting the toroidal magnetic field such that the ion B×∇B drift direction is pointed away from the X-point. However, measurements of W content in the plasma core for both toroidal magnetic field directions suggest the presence of additional, unmeasured sources of erosion. The difference in the measured core W density with OSP position is much greater than the difference in the measured erosion rates, which may suggest that the leakage of eroded impurities out of the divertor is governed primarily through the parallel ion temperature gradient and friction forces.

AB - A series of L-mode plasma discharges was performed in the DIII-D tokamak to assess the impact of outer strike point (OSP) position and toroidal magnetic field direction on erosion and core contamination potential of the recently-installed, tungsten-coated Small Angle Slot (SAS-VW) divertor. In one discharge, in-slot emission spectroscopy measured an < 48 % increase in the W gross erosion rate when the OSP was moved 3 cm outwards, away from the V-shaped vertex of the slot divertor. However, the effective W yield (erosion rate divided by the incident D flux) was, overall, insensitive to changes in OSP location. Consistently low estimates of the effective W yield based on measurements taken a few cm outwards from the vertex suggest potentially significant C surface contamination. No W emission signal was detected when orienting the toroidal magnetic field such that the ion B×∇B drift direction is pointed away from the X-point. However, measurements of W content in the plasma core for both toroidal magnetic field directions suggest the presence of additional, unmeasured sources of erosion. The difference in the measured core W density with OSP position is much greater than the difference in the measured erosion rates, which may suggest that the leakage of eroded impurities out of the divertor is governed primarily through the parallel ion temperature gradient and friction forces.

KW - Divertor

KW - Optical spectroscopy

KW - Plasma-material interactions

KW - Tokamaks

KW - Tungsten

UR - https://www.scopus.com/pages/publications/85216857595

U2 - 10.1016/j.nme.2025.101884

DO - 10.1016/j.nme.2025.101884

M3 - Article

AN - SCOPUS:85216857595

SN - 2352-1791

VL - 42

JO - Nuclear Materials and Energy

JF - Nuclear Materials and Energy

M1 - 101884

ER -

Tungsten erosion during L-mode discharges in the DIII-D SAS-VW divertor

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Keywords

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