Pedestal collapse by resonant magnetic perturbations
Abstract
Pedestal collapse (i.e., the complete loss of the edge transport barrier (ETB)) in DIII-D H-mode plasmas occurs when resonant magnetic perturbations (RMPs) penetrate the steep gradient region at the plasma edge. Normally, RMP driven magnetic islands can occur at the top and bottom of the H-mode pedestal and these islands generate conditions consistent with edge-localized-mode (ELM) suppression and density pump-out, respectively, based on nonlinear two-fluid MHD simulations. In contrast, MHD simulations show that the steep pressure gradient region between the top and bottom of the DIII-D pedestal is generally immune to resonant field penetration due to large local E × B and diamagnetic flows. By this fortuitous circumstance, the edge-transport-barrier and H-mode confinement can be maintained while achieving ELM suppression. However, pedestal collapse can occur in DIII-D when the screening flows are inadequate to prevent field penetration in the steep gradient region of the pedestal. Non-linear two-fluid MHD simulations support the role of resonant field penetration in pedestal collapse for DIII-D H-mode plasmas with weak edge E × B and diamagnetic screening flows. ITER will likely have weaker edge screening flows than present experiments due to its much larger size, making it more susceptible to resonant field penetration in themore »
- Authors:
-
[1];
[1];
[1];
[2];
[1];
[3];
[4];
[2];
[1];
[5]
- Princeton Plasma Physics Lab. (PPPL), Princeton, NJ (United States)
- General Atomics, San Diego, CA (United States)
- Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
- Univ. of California, San Diego, CA (United States)
- Max-Plank-Inst. fur Plasmaphysik, Garching (Germany)
- Publication Date:
- Research Org.:
- Princeton Plasma Physics Lab. (PPPL), Princeton, NJ (United States); General Atomics, San Diego, CA (United States); Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
- Sponsoring Org.:
- USDOE Office of Science (SC), Fusion Energy Sciences (FES); USDOE National Nuclear Security Administration (NNSA)
- OSTI Identifier:
- 1775294
- Alternate Identifier(s):
- OSTI ID: 1778843; OSTI ID: 1811229
- Report Number(s):
- LLNL-JRNL-824431
Journal ID: ISSN 0029-5515; TRN: US2209328
- Grant/Contract Number:
- AC02-09CH11466, FC02-04ER54698; FG02-05ER54809; AC52-07NA27344
- Resource Type:
- Accepted Manuscript
- Journal Name:
- Nuclear Fusion
- Additional Journal Information:
- Journal Volume: 61; Journal Issue: 4; Journal ID: ISSN 0029-5515
- Publisher:
- IOP Science
- Country of Publication:
- United States
- Language:
- English
- Subject:
- 73 NUCLEAR PHYSICS AND RADIATION PHYSICS; resonant magnetic perturbations; edge transport barrier; ELM suppression
Citation Formats
Nazikian, R., Hu, Q., Ashourvan, A., Eldon, D., Evans, T. E., Grierson, B. A., Logan, N. C., Orlov, D. M., Park, J. -K., Paz-Soldan, C., Poli, F. M., and Yu, Q. Pedestal collapse by resonant magnetic perturbations. United States: N. p., 2021.
Web. doi:10.1088/1741-4326/abd863.
Nazikian, R., Hu, Q., Ashourvan, A., Eldon, D., Evans, T. E., Grierson, B. A., Logan, N. C., Orlov, D. M., Park, J. -K., Paz-Soldan, C., Poli, F. M., & Yu, Q. Pedestal collapse by resonant magnetic perturbations. United States. https://doi.org/10.1088/1741-4326/abd863
Nazikian, R., Hu, Q., Ashourvan, A., Eldon, D., Evans, T. E., Grierson, B. A., Logan, N. C., Orlov, D. M., Park, J. -K., Paz-Soldan, C., Poli, F. M., and Yu, Q. Mon .
"Pedestal collapse by resonant magnetic perturbations". United States. https://doi.org/10.1088/1741-4326/abd863. https://www.osti.gov/servlets/purl/1775294.
@article{osti_1775294,
title = {Pedestal collapse by resonant magnetic perturbations},
author = {Nazikian, R. and Hu, Q. and Ashourvan, A. and Eldon, D. and Evans, T. E. and Grierson, B. A. and Logan, N. C. and Orlov, D. M. and Park, J. -K. and Paz-Soldan, C. and Poli, F. M. and Yu, Q.},
abstractNote = {Pedestal collapse (i.e., the complete loss of the edge transport barrier (ETB)) in DIII-D H-mode plasmas occurs when resonant magnetic perturbations (RMPs) penetrate the steep gradient region at the plasma edge. Normally, RMP driven magnetic islands can occur at the top and bottom of the H-mode pedestal and these islands generate conditions consistent with edge-localized-mode (ELM) suppression and density pump-out, respectively, based on nonlinear two-fluid MHD simulations. In contrast, MHD simulations show that the steep pressure gradient region between the top and bottom of the DIII-D pedestal is generally immune to resonant field penetration due to large local E × B and diamagnetic flows. By this fortuitous circumstance, the edge-transport-barrier and H-mode confinement can be maintained while achieving ELM suppression. However, pedestal collapse can occur in DIII-D when the screening flows are inadequate to prevent field penetration in the steep gradient region of the pedestal. Non-linear two-fluid MHD simulations support the role of resonant field penetration in pedestal collapse for DIII-D H-mode plasmas with weak edge E × B and diamagnetic screening flows. ITER will likely have weaker edge screening flows than present experiments due to its much larger size, making it more susceptible to resonant field penetration in the steep gradient region of the pedestal. Analysis of model ITER equilibria demonstrates that resonant field penetration in the steep pressure gradient region is possible for RMP levels of the order required for ELM suppression. The effect of such penetration on the ITER pedestal will depend sensitively on the resulting degree of island overlap.},
doi = {10.1088/1741-4326/abd863},
journal = {Nuclear Fusion},
number = 4,
volume = 61,
place = {United States},
year = {Mon Mar 08 00:00:00 EST 2021},
month = {Mon Mar 08 00:00:00 EST 2021}
}
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