skip to main content
OSTI.GOV title logo U.S. Department of Energy
Office of Scientific and Technical Information

Title: M3D-C1 simulations of the plasma response to RMPs in NSTX-U single-null and snowflake divertor configurations

Abstract

Here in this work, single- and two-fluid resistive magnetohydrodynamic calculations of the plasma response to n = 3 magnetic perturbations in single-null (SN) and snowflake (SF) divertor configurations are compared with those based on the vacuum approach. The calculations are performed using the code M3D-C 1 and are based on simulated NSTX-U plasmas. Significantly different plasma responses were found from these calculations, with the difference between the single- and two-fluid plasma responses being caused mainly by the different screening mechanism intrinsic to each of these models. Although different plasma responses were obtained from these different plasma models, no significant difference between the SN and SF plasma responses were found. However, due to their different equilibrium properties, magnetic perturbations cause the SF configuration to develop additional and longer magnetic lobes in the null-point region than the SN, regardless of the plasma model used. The intersection of these longer and additional lobes with the divertor plates are expected to cause more striations in the particle and heat flux target profiles. In addition, the results indicate that the size of the magnetic lobes, in both single-null and snowflake configurations, are more sensitive to resonant magnetic perturbations than to non-resonant magnetic perturbations.

Authors:
 [1];  [2];  [3];  [3];  [2];  [4];  [2];  [4];  [5];  [6];  [6];  [7];  [6];  [8]
  1. General Atomics, San Diego, CA (United States); Oak Ridge Associated Univ., Oak Ridge, TN (United States)
  2. Princeton Plasma Physics Lab. (PPPL), Princeton, NJ (United States)
  3. General Atomics, San Diego, CA (United States)
  4. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
  5. Univ. of Sao Paulo (Brazil). Dept. of Applied Physics
  6. Univ. of Wisconsin, Madison, WI (United States). Dept. of Engineering Physics
  7. Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
  8. Columbia Univ., New York, NY (United States). Dept. of Applied Physics and Applied Mathematics
Publication Date:
Research Org.:
Princeton Plasma Physics Lab. (PPPL), Princeton, NJ (United States); General Atomics, San Diego, CA (United States); Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
Sponsoring Org.:
USDOE Office of Science (SC), Fusion Energy Sciences (FES) (SC-24); USDOE Office of Nuclear Energy (NE)
OSTI Identifier:
1373377
Alternate Identifier(s):
OSTI ID: 1374813; OSTI ID: 1376338
Grant/Contract Number:
SC0012706; FC02-04ER54698; AC05-06OR23100; AC02-09CH11466; AC05-00OR22725; SC0012315; SC0013911; AC52-07NA27344; SC0008520
Resource Type:
Journal Article: Accepted Manuscript
Journal Name:
Nuclear Fusion
Additional Journal Information:
Journal Volume: 57; Journal Issue: 7; Journal ID: ISSN 0029-5515
Publisher:
IOP Science
Country of Publication:
United States
Language:
English
Subject:
70 PLASMA PHYSICS AND FUSION TECHNOLOGY; snowflake divertor; RMP; plasma response; two-fluid MHD

Citation Formats

Canal, G. P., Ferraro, N. M., Evans, T. E., Osborne, T. H., Menard, J. E., Ahn, J. -W., Maingi, R., Wingen, A., Ciro, D., Frerichs, H., Schmitz, O., Soukhanoviskii, V., Waters, I., and Sabbagh, S. A. M3D-C1 simulations of the plasma response to RMPs in NSTX-U single-null and snowflake divertor configurations. United States: N. p., 2017. Web. doi:10.1088/1741-4326/aa6e10.
Canal, G. P., Ferraro, N. M., Evans, T. E., Osborne, T. H., Menard, J. E., Ahn, J. -W., Maingi, R., Wingen, A., Ciro, D., Frerichs, H., Schmitz, O., Soukhanoviskii, V., Waters, I., & Sabbagh, S. A. M3D-C1 simulations of the plasma response to RMPs in NSTX-U single-null and snowflake divertor configurations. United States. doi:10.1088/1741-4326/aa6e10.
Canal, G. P., Ferraro, N. M., Evans, T. E., Osborne, T. H., Menard, J. E., Ahn, J. -W., Maingi, R., Wingen, A., Ciro, D., Frerichs, H., Schmitz, O., Soukhanoviskii, V., Waters, I., and Sabbagh, S. A. Thu . "M3D-C1 simulations of the plasma response to RMPs in NSTX-U single-null and snowflake divertor configurations". United States. doi:10.1088/1741-4326/aa6e10. https://www.osti.gov/servlets/purl/1373377.
@article{osti_1373377,
title = {M3D-C1 simulations of the plasma response to RMPs in NSTX-U single-null and snowflake divertor configurations},
author = {Canal, G. P. and Ferraro, N. M. and Evans, T. E. and Osborne, T. H. and Menard, J. E. and Ahn, J. -W. and Maingi, R. and Wingen, A. and Ciro, D. and Frerichs, H. and Schmitz, O. and Soukhanoviskii, V. and Waters, I. and Sabbagh, S. A.},
abstractNote = {Here in this work, single- and two-fluid resistive magnetohydrodynamic calculations of the plasma response to n = 3 magnetic perturbations in single-null (SN) and snowflake (SF) divertor configurations are compared with those based on the vacuum approach. The calculations are performed using the code M3D-C1 and are based on simulated NSTX-U plasmas. Significantly different plasma responses were found from these calculations, with the difference between the single- and two-fluid plasma responses being caused mainly by the different screening mechanism intrinsic to each of these models. Although different plasma responses were obtained from these different plasma models, no significant difference between the SN and SF plasma responses were found. However, due to their different equilibrium properties, magnetic perturbations cause the SF configuration to develop additional and longer magnetic lobes in the null-point region than the SN, regardless of the plasma model used. The intersection of these longer and additional lobes with the divertor plates are expected to cause more striations in the particle and heat flux target profiles. In addition, the results indicate that the size of the magnetic lobes, in both single-null and snowflake configurations, are more sensitive to resonant magnetic perturbations than to non-resonant magnetic perturbations.},
doi = {10.1088/1741-4326/aa6e10},
journal = {Nuclear Fusion},
number = 7,
volume = 57,
place = {United States},
year = {Thu Apr 20 00:00:00 EDT 2017},
month = {Thu Apr 20 00:00:00 EDT 2017}
}

Journal Article:
Free Publicly Available Full Text
Publisher's Version of Record

Save / Share:
  • Non-axisymmetric control coils and the so-called snow ake divertor con guration are two potential solutions proposed to solve two separate outstanding issues on the path towards self-sustained burning plasma operations, namely the transient energy bursts caused by edge localized modes and the steady state heat exhaust problem. In a reactor, these two proposed solutions would have to operate simultaneously and it is, therefore, important to investigate their compatibility and to identify possible con icts that could prevent them from operating simultaneously. In this work, single- and two- uid resistive magnetohydrodynamic calculations are used to investigate the e ect of externallymore » applied n = 3 magnetic perturbations on the snow ake divertor con guration. The calculations are performed using the code M3D-C1 and are based on simulated NSTX-U plasmas. The results show that additional and longer magnetic lobes are created in the null-point region of the snow ake con guration, compared to those in the conventional single-null. The intersection of these longer and additional lobes with the divertor plates are expected to cause more striations in the particle and heat ux target pro les. In addition, the results indicate that the size of the magnetic lobes, in both single-null and snow ake con gurations, are more sensitive to resonant magnetic perturbations than to non-resonant magnetic perturbations. The results also suggest that lower values of current in nonaxisymmetric control coils closer to the null-point region would be required to suppress edge localized modes. This e ect is expected to be enhanced in plasmas with the snow ake con guration.« less
  • In this work, single- and two-fluid resistive magnetohydrodynamic calculations of the plasma response to $n=3$ magnetic perturbations in single-null (SN) and snowflake (SF) divertor configurations are compared with those based on the vacuum approach. The calculations are performed using the code M3D-C1 and are based on simulated NSTX-U plasmas. Significantly different plasma responses were found from these calculations, with the difference between the single- and two-fluid plasma responses being caused mainly by the different screening mechanism intrinsic to each of these models. Although different plasma responses were obtained from these different plasma models, no significant difference between the SN andmore » SF plasma responses were found. However, due to their different equilibrium properties, magnetic perturbations cause the SF configuration to develop additional and longer magnetic lobes in the null-point region than the SN, regardless of the plasma model used. The intersection of these longer and additional lobes with the divertor plates are expected to cause more striations in the particle and heat flux target profiles. Additionally, the results indicate that the size of the magnetic lobes, in both single-null and snowflake configurations, are more sensitive to resonant magnetic perturbations than to non-resonant magnetic perturbations.« less
  • Experimental results from the National Spherical Torus Experiment (NSTX), a medium-size spherical tokamak with a compact divertor, and DIII-D, a large conventional aspect ratio tokamak, demonstrate that the snowflake (SF) divertor configuration may provide a promising solution for mitigating divertor heat loads and target plate erosion compatible with core H-mode confinement in future fusion devices, where the standard radiative divertor solution may be inadequate. In NSTX, where the initial high-power SF experiment were performed, the SF divertor was compatible with H-mode confinement, and led to the destabilization of large ELMs. However, a stable partial detachment of the outer strike pointmore » was also achieved where inter-ELM peak heat flux was reduced by factors 3-5, and peak ELM heat flux was reduced by up to 80% (cf. standard divertor). The DIII-D studies show the SF divertor enables significant power spreading in attached and radiative divertor conditions. Results include: compatibility with the core and pedestal, peak inter-ELM divertor heat flux reduction due to geometry at lower n e, and ELM energy and divertor peak heat flux reduction, especially prominent in radiative D 2-seeded SF divertor, and nearly complete power detachment and broader radiated power distribution in the radiative D 2-seeded SF divertor at P SOL = 3 - 4 MW. A variety of SF configurations can be supported by the divertor coil set in NSTX Upgrade. Edge transport modeling with the multi-fluid edge transport code UEDGE shows that the radiative SF divertor can successfully reduce peak divertor heat flux for the projected P SOL ≃9 MW case. In conclusion, the radiative SF divertor with carbon impurity provides a wider n e operating window, 50% less argon is needed in the impurity-seeded SF configuration to achieve similar q peak reduction factors (cf. standard divertor).« less
  • Experimental results from the National Spherical Torus Experiment (NSTX), a medium-size spherical tokamak with a compact divertor, and DIII-D, a large conventional aspect ratio tokamak, demonstrate that the snowflake (SF) divertor configuration may provide a promising solution for mitigating divertor heat loads and target plate erosion compatible with core H-mode confinement in the future fusion devices, where the standard radiative divertor solution may be inadequate. In NSTX, where the initial high-power SF experiment was performed, the SF divertor was compatible with H-mode confinement, and led to the destabilization of large Edge Localized Modes (ELMs). However, a stable partial detachment ofmore » the outer strike point was also achieved where inter-ELM peak heat flux was reduced by factors 3-5, and peak ELM heat flux was reduced by up to 80% (see standard divertor). The DIII-D studies show the SF divertor enables significant power spreading in attached and radiative divertor conditions. Results include: compatibility with the core and pedestal, peak inter-ELM divertor heat flux reduction due to geometry at lower ne, and ELM energy and divertor peak heat flux reduction, especially prominent in radiative D 2-seeded SF divertor, and nearly complete power detachment and broader radiated power distribution in the radiative D 2-seeded SF divertor at PSOL = 3 - 4 MW. A variety of SF configurations can be supported by the divertor coil set in NSTX Upgrade. Edge transport modeling with the multifluid edge transport code UEDGE shows that the radiative SF divertor can successfully reduce peak divertor heat flux for the projected PSOL ≃ 9 MW case. Furthermore, the radiative SF divertor with carbon impurity provides a wider ne operating window, 50% less argon is needed in the impurity-seeded SF configuration to achieve similar q peak reduction factors (see standard divertor).« less