Modeling of 3D magnetic equilibrium effects on edge turbulence stability during RMP ELM suppression in tokamaks
Some recent experimental observations have found turbulent fluctuation structures that are nonaxisymmetric in a tokamak with applied 3D fields. Here, two fluid resistive effects are shown to produce changes relevant to turbulent transport in the modeled 3D magnetohydrodynamic (MHD) equilibrium of tokamak pedestals with these 3D fields applied. Ideal MHD models are insufficient to reproduce the relevant effects. By calculating the ideal 3D equilibrium using the VMEC code, the geometric shaping parameters that determine linear turbulence stability, including the normal curvature and local magnetic shear, are shown to be only weakly modified by applied 3D fields in the DIIID tokamak. These ideal MHD effects are therefore not sufficient to explain the observed changes to fluctuations and transport. Using the M3DC1 code to model the 3D equilibrium, density is shown to be redistributed on flux surfaces in the pedestal when resistive two fluid effects are included, while islands are screened by rotation in this region. Furthermore, the redistribution of density results in density and pressure gradient scale lengths that vary within pedestal flux surfaces between different helically localized flux tubes. This would produce different drive terms for trapped electron mode and kinetic ballooning mode turbulence, the latter of which is expectedmore »
 Authors:

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 Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
 Princeton Plasma Physics Lab. (PPPL), Princeton, NJ (United States)
 General Atomics, San Diego, CA (United States)
 Publication Date:
 Grant/Contract Number:
 FC0204ER54698; AC0500OR22725; AC0209CH11466
 Type:
 Accepted Manuscript
 Journal Name:
 Nuclear Fusion
 Additional Journal Information:
 Journal Volume: 57; Journal Issue: 11; Journal ID: ISSN 00295515
 Publisher:
 IOP Science
 Research Org:
 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) (SC24)
 Country of Publication:
 United States
 Language:
 English
 Subject:
 70 PLASMA PHYSICS AND FUSION TECHNOLOGY; RMP; equilibrium; turbulence
 OSTI Identifier:
 1376604
 Alternate Identifier(s):
 OSTI ID: 1374600
Wilcox, R. S., Wingen, Andreas, Cianciosa, Mark R., Ferraro, Nathaniel M., Hirshman, S. P., PazSoldan, Carlos, Shafer, Morgan W., and Unterberg, Ezekial A.. Modeling of 3D magnetic equilibrium effects on edge turbulence stability during RMP ELM suppression in tokamaks. United States: N. p.,
Web. doi:10.1088/17414326/aa7bad.
Wilcox, R. S., Wingen, Andreas, Cianciosa, Mark R., Ferraro, Nathaniel M., Hirshman, S. P., PazSoldan, Carlos, Shafer, Morgan W., & Unterberg, Ezekial A.. Modeling of 3D magnetic equilibrium effects on edge turbulence stability during RMP ELM suppression in tokamaks. United States. doi:10.1088/17414326/aa7bad.
Wilcox, R. S., Wingen, Andreas, Cianciosa, Mark R., Ferraro, Nathaniel M., Hirshman, S. P., PazSoldan, Carlos, Shafer, Morgan W., and Unterberg, Ezekial A.. 2017.
"Modeling of 3D magnetic equilibrium effects on edge turbulence stability during RMP ELM suppression in tokamaks". United States.
doi:10.1088/17414326/aa7bad. https://www.osti.gov/servlets/purl/1376604.
@article{osti_1376604,
title = {Modeling of 3D magnetic equilibrium effects on edge turbulence stability during RMP ELM suppression in tokamaks},
author = {Wilcox, R. S. and Wingen, Andreas and Cianciosa, Mark R. and Ferraro, Nathaniel M. and Hirshman, S. P. and PazSoldan, Carlos and Shafer, Morgan W. and Unterberg, Ezekial A.},
abstractNote = {Some recent experimental observations have found turbulent fluctuation structures that are nonaxisymmetric in a tokamak with applied 3D fields. Here, two fluid resistive effects are shown to produce changes relevant to turbulent transport in the modeled 3D magnetohydrodynamic (MHD) equilibrium of tokamak pedestals with these 3D fields applied. Ideal MHD models are insufficient to reproduce the relevant effects. By calculating the ideal 3D equilibrium using the VMEC code, the geometric shaping parameters that determine linear turbulence stability, including the normal curvature and local magnetic shear, are shown to be only weakly modified by applied 3D fields in the DIIID tokamak. These ideal MHD effects are therefore not sufficient to explain the observed changes to fluctuations and transport. Using the M3DC1 code to model the 3D equilibrium, density is shown to be redistributed on flux surfaces in the pedestal when resistive two fluid effects are included, while islands are screened by rotation in this region. Furthermore, the redistribution of density results in density and pressure gradient scale lengths that vary within pedestal flux surfaces between different helically localized flux tubes. This would produce different drive terms for trapped electron mode and kinetic ballooning mode turbulence, the latter of which is expected to be the limiting factor for pedestal pressure gradients in DIIID.},
doi = {10.1088/17414326/aa7bad},
journal = {Nuclear Fusion},
number = 11,
volume = 57,
place = {United States},
year = {2017},
month = {7}
}