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Title: Tungsten erosion by unipolar arcing in DIII-D

Abstract

Here, unipolar arcing was an important mechanism of metal surface erosion during the recently conducted Metal Rings Campaign in DIII-D when two toroidally continuous tile rings with 5 cm wide W-coated TZM inserts were installed in graphite tiles in the lower divertor, one on the floor and one on the shelf. Most of the arc damage occurred on the shelf ring. The total amount of W removed by arcing from the affected ~4% of the shelf ring area was estimated ~0.8 × 10 21 at., about half of the total amount of W eroded and redeposited outside the inserts (1.8 ± 0.9)×10 21 at. The rings were exposed for a total of ~480 discharges, an equivalent of plasma time on W surfaces (with $${{I}}_{{\rm{p}}}\gt 0.5$$ MA) ~10 3 s. Arcing was monitored in situ with WI (400.9 nm) filtered camera and photomultipliers and showed that: (i) arcing only occurred during ELMs and disruptions, (ii) arcing rate was much lower on the floor than on the shelf ring, and (iii) arcing had a low cut off power flux density about 2 MW m –2. About half of arc tracks had large $${10}^{\circ }$$ pitch angle and probably were produced during disruptions. Such tracks were only found on the shelf. Moderate toroidal variation of the arc track density and W erosion with nearly n = 1 pattern has been measured.

Authors:
ORCiD logo [1]; ORCiD logo [2]; ORCiD logo [2];  [1]; ORCiD logo [3];  [4];  [1]; ORCiD logo [1]; ORCiD logo [1];  [2]; ORCiD logo [5]; ORCiD logo [1];  [6];  [6];  [6]
  1. Univ. of California (San Diego), La Jolla, CA (United States)
  2. General Atomics, San Diego, CA (United States)
  3. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
  4. Sandia National Lab. (SNL-NM), Albuquerque, NM (United States)
  5. Univ. of Wisconsin-Madison, Madison, WI (United States)
  6. Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
Publication Date:
Research Org.:
Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
Sponsoring Org.:
USDOE Office of Science (SC)
OSTI Identifier:
1483171
Grant/Contract Number:  
AC05-00OR22725
Resource Type:
Journal Article: Accepted Manuscript
Journal Name:
Physica Scripta
Additional Journal Information:
Journal Volume: T170; Journal Issue: T170; Journal ID: ISSN 0031-8949
Publisher:
IOP Publishing
Country of Publication:
United States
Language:
English
Subject:
70 PLASMA PHYSICS AND FUSION TECHNOLOGY; DIII-D; arcing; tungsten; erosion

Citation Formats

Bykov, Igor, Chrobak, C. P., Abrams, Tyler, Rudakov, D. L., Unterberg, Ezekial A., Wampler, W. R., Hollmann, E. M., Moyer, R. A., Boedo, J. A., Stahl, B., Hinson, Edward T., Yu, J. H., Lasnier, C. J., Makowski, M., and McLean, A. G. Tungsten erosion by unipolar arcing in DIII-D. United States: N. p., 2017. Web. doi:10.1088/1402-4896/aa8e34.
Bykov, Igor, Chrobak, C. P., Abrams, Tyler, Rudakov, D. L., Unterberg, Ezekial A., Wampler, W. R., Hollmann, E. M., Moyer, R. A., Boedo, J. A., Stahl, B., Hinson, Edward T., Yu, J. H., Lasnier, C. J., Makowski, M., & McLean, A. G. Tungsten erosion by unipolar arcing in DIII-D. United States. doi:10.1088/1402-4896/aa8e34.
Bykov, Igor, Chrobak, C. P., Abrams, Tyler, Rudakov, D. L., Unterberg, Ezekial A., Wampler, W. R., Hollmann, E. M., Moyer, R. A., Boedo, J. A., Stahl, B., Hinson, Edward T., Yu, J. H., Lasnier, C. J., Makowski, M., and McLean, A. G. Fri . "Tungsten erosion by unipolar arcing in DIII-D". United States. doi:10.1088/1402-4896/aa8e34. https://www.osti.gov/servlets/purl/1483171.
@article{osti_1483171,
title = {Tungsten erosion by unipolar arcing in DIII-D},
author = {Bykov, Igor and Chrobak, C. P. and Abrams, Tyler and Rudakov, D. L. and Unterberg, Ezekial A. and Wampler, W. R. and Hollmann, E. M. and Moyer, R. A. and Boedo, J. A. and Stahl, B. and Hinson, Edward T. and Yu, J. H. and Lasnier, C. J. and Makowski, M. and McLean, A. G.},
abstractNote = {Here, unipolar arcing was an important mechanism of metal surface erosion during the recently conducted Metal Rings Campaign in DIII-D when two toroidally continuous tile rings with 5 cm wide W-coated TZM inserts were installed in graphite tiles in the lower divertor, one on the floor and one on the shelf. Most of the arc damage occurred on the shelf ring. The total amount of W removed by arcing from the affected ~4% of the shelf ring area was estimated ~0.8 × 1021 at., about half of the total amount of W eroded and redeposited outside the inserts (1.8 ± 0.9)×1021 at. The rings were exposed for a total of ~480 discharges, an equivalent of plasma time on W surfaces (with ${{I}}_{{\rm{p}}}\gt 0.5$ MA) ~103 s. Arcing was monitored in situ with WI (400.9 nm) filtered camera and photomultipliers and showed that: (i) arcing only occurred during ELMs and disruptions, (ii) arcing rate was much lower on the floor than on the shelf ring, and (iii) arcing had a low cut off power flux density about 2 MW m–2. About half of arc tracks had large ${10}^{\circ }$ pitch angle and probably were produced during disruptions. Such tracks were only found on the shelf. Moderate toroidal variation of the arc track density and W erosion with nearly n = 1 pattern has been measured.},
doi = {10.1088/1402-4896/aa8e34},
journal = {Physica Scripta},
issn = {0031-8949},
number = T170,
volume = T170,
place = {United States},
year = {2017},
month = {10}
}

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