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Title: Measurement and modeling of magnetic configurations to mimic overload scenarios in the W7-X stellarator

Abstract

Experiments were performed during the first divertor operational phase (OP1.2a) of the Wendelstein 7-X stellarator to verify predictions of potential overload conditions corresponding to certain high-power long-pulse OP2 scenarios. A potential solution to this overload is the installation of new divertor components called scraper elements, which are designed to intercept heat flux that would otherwise be incident on low-rated divertor edges. Heat flux measurements were obtained in a series of magnetic configurations designed to mimic the magnetic topology evolution caused by net toroidal current and beta, which is not directly accessible in OP1.2a. The experimental flux patterns are qualitatively reproduced in position and magnitude for by field line diffusion simulations using ad hoc cross-field diffusivities near the value used to design the scraper element. However, some important differences are observed, including a shift towards the pumping gap and low-rated components. Potential sources of discrepancy such as toroidal current evolution and error fields are discussed. In conclusion, a shift in the experimental heat flux pattern due to increasing toroidal current is observed in a 12 s discharge.

Authors:
ORCiD logo [1];  [2];  [3];  [3];  [3];  [3]; ORCiD logo [4]; ORCiD logo [5];  [3];  [3];  [3];  [6];  [7];  [7]; ORCiD logo [7]; ORCiD logo [1]; ORCiD logo [1];  [8]; ORCiD logo [9];  [9]
  1. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
  2. Forschungszentrum Juelich GmbH, Juelich (Germany); Max Planck Institute for Plasma Physics, Greifswald (Germany)
  3. Max Planck Institute for Plasma Physics, Greifswald (Germany)
  4. Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
  5. Princeton Plasma Physics Lab. (PPPL), Princeton, NJ (United States)
  6. Princeton Univ., Princeton, NJ (United States)
  7. Univ. of Wisconsin-Madison, Madison, WI (United States)
  8. Max Planck Institute for Plasma Physics, Garching (Germany)
  9. Univ. of Cagliari, Cagliari (Italy)
Publication Date:
Research Org.:
Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
Sponsoring Org.:
USDOE Office of Science (SC); USDOE Office of Science (SC). Fusion Energy Sciences (FES) (SC-24)
Contributing Org.:
the W7-X team
OSTI Identifier:
1515676
Alternate Identifier(s):
OSTI ID: 1526965
Report Number(s):
LA-UR-19-23945
Journal ID: ISSN 0029-5515
Grant/Contract Number:  
AC05-00OR22725; 89233218CNA000001
Resource Type:
Journal Article: Accepted Manuscript
Journal Name:
Nuclear Fusion
Additional Journal Information:
Journal Volume: 59; Journal Issue: 6; Journal ID: ISSN 0029-5515
Publisher:
IOP Science
Country of Publication:
United States
Language:
English
Subject:
70 PLASMA PHYSICS AND FUSION TECHNOLOGY; Wendelstein 7-X stellarator; heat flux; scraper element; Magnetic Fusion Energy

Citation Formats

Lore, Jeremy D., Gao, Y., Geiger, J., Hoelbe, H., Niemann, H., Jakubowski, M., Wurden, G. A., Lazerson, S., Drewelow, P., Ali, A., Sitjes, A. Puig, LeViness, A., Frerichs, Heinke, Barbui, T., Effenberg, F., Harris, Jeffrey, Lumsdaine, Arnold, Boscary, J., Pisano, F., and Cannas, B. Measurement and modeling of magnetic configurations to mimic overload scenarios in the W7-X stellarator. United States: N. p., 2019. Web. doi:10.1088/1741-4326/ab18d1.
Lore, Jeremy D., Gao, Y., Geiger, J., Hoelbe, H., Niemann, H., Jakubowski, M., Wurden, G. A., Lazerson, S., Drewelow, P., Ali, A., Sitjes, A. Puig, LeViness, A., Frerichs, Heinke, Barbui, T., Effenberg, F., Harris, Jeffrey, Lumsdaine, Arnold, Boscary, J., Pisano, F., & Cannas, B. Measurement and modeling of magnetic configurations to mimic overload scenarios in the W7-X stellarator. United States. doi:10.1088/1741-4326/ab18d1.
Lore, Jeremy D., Gao, Y., Geiger, J., Hoelbe, H., Niemann, H., Jakubowski, M., Wurden, G. A., Lazerson, S., Drewelow, P., Ali, A., Sitjes, A. Puig, LeViness, A., Frerichs, Heinke, Barbui, T., Effenberg, F., Harris, Jeffrey, Lumsdaine, Arnold, Boscary, J., Pisano, F., and Cannas, B. Mon . "Measurement and modeling of magnetic configurations to mimic overload scenarios in the W7-X stellarator". United States. doi:10.1088/1741-4326/ab18d1. https://www.osti.gov/servlets/purl/1515676.
@article{osti_1515676,
title = {Measurement and modeling of magnetic configurations to mimic overload scenarios in the W7-X stellarator},
author = {Lore, Jeremy D. and Gao, Y. and Geiger, J. and Hoelbe, H. and Niemann, H. and Jakubowski, M. and Wurden, G. A. and Lazerson, S. and Drewelow, P. and Ali, A. and Sitjes, A. Puig and LeViness, A. and Frerichs, Heinke and Barbui, T. and Effenberg, F. and Harris, Jeffrey and Lumsdaine, Arnold and Boscary, J. and Pisano, F. and Cannas, B.},
abstractNote = {Experiments were performed during the first divertor operational phase (OP1.2a) of the Wendelstein 7-X stellarator to verify predictions of potential overload conditions corresponding to certain high-power long-pulse OP2 scenarios. A potential solution to this overload is the installation of new divertor components called scraper elements, which are designed to intercept heat flux that would otherwise be incident on low-rated divertor edges. Heat flux measurements were obtained in a series of magnetic configurations designed to mimic the magnetic topology evolution caused by net toroidal current and beta, which is not directly accessible in OP1.2a. The experimental flux patterns are qualitatively reproduced in position and magnitude for by field line diffusion simulations using ad hoc cross-field diffusivities near the value used to design the scraper element. However, some important differences are observed, including a shift towards the pumping gap and low-rated components. Potential sources of discrepancy such as toroidal current evolution and error fields are discussed. In conclusion, a shift in the experimental heat flux pattern due to increasing toroidal current is observed in a 12 s discharge.},
doi = {10.1088/1741-4326/ab18d1},
journal = {Nuclear Fusion},
issn = {0029-5515},
number = 6,
volume = 59,
place = {United States},
year = {2019},
month = {5}
}

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