Analysis of equilibrium and turbulent fluxes across the separatrix in a gyrokinetic simulation

Keramidas Charidakos, I.; Myra, J. R.; Parker, S.; Ku, S.; Churchill, R. M.; Hager, R.; Chang, C. S.

doi:10.1063/1.5037723

Title: Analysis of equilibrium and turbulent fluxes across the separatrix in a gyrokinetic simulation

Journal Article · 23 July 2018 · Physics of Plasmas

DOI: https://doi.org/10.1063/1.5037723 · OSTI ID:1466035

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^[2]; Parker, S. ^[1]; Ku, S. ^[3]; Churchill, R. M. ^[3];

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Univ. of Colorado, Boulder, CO (United States). Dept. of Physics
Lodestar Research Corporation, Boulder, CO (United States)
Princeton Plasma Physics Lab. (PPPL), Princeton, NJ (United States); Princeton Univ., NJ (United States)

The SOL width is a parameter of paramount importance in modern tokamaks as it controls the power density deposited at the divertor plates, critical for plasma-facing material survivability. An understanding of the parameters controlling it has consequently long been sought. Prior to Chang et al. (2017 NF 57 11), studies of the tokamak edge have been mostly confined to reduced fluid models and simplified geometries, leaving out important pieces of physics. Here, we analyze the results of a DIII-D simulation performed with the full-f gyrokinetic code XGC1 which includes both turbulence and neoclassical effects in realistic divertor geometry. More specifically, we calculate the particle and heat E x B fluxes along the separatrix, discriminating between equilibrium and turbulent contributions. We find that the density SOL width is impacted almost exclusively by the turbulent electron flux. In this simulation, the level of edge turbulence is regulated by a mechanism we are only beginning to understand: grad-B-drifts and ion X-point losses at the top and bottom of the machine, along with ion banana orbits at the low field side (LFS), result in a complex poloidal potential structure at the separatrix which is the cause of the E x B drift pattern that we observe. Turbulence is being suppressed by the shear flows that this potential generates. At the same time, turbulence, along with increased edge collisionality and electron inertia, can influence the shape of the potential structure by making the electrons non-adiabatic. Furthermore, being the only means through which the electrons can lose confinement, it needs to be in a balance with the original direct ion orbit losses to maintain charge neutrality.

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Research Organization:: Oak Ridge National Laboratory (ORNL), Oak Ridge, TN (United States). Oak Ridge Leadership Computing Facility (OLCF); Lodestar Research Corp., Boulder, CO (United States)

Sponsoring Organization:: USDOE Office of Science (SC), Fusion Energy Sciences (FES)

Grant/Contract Number:: FG02-97ER54392; SO15882-C

OSTI ID:: 1466035

Alternate ID(s):: OSTI ID: 1461242

Report Number(s):: DOE-ER/54392-90; PPPL/SO15882C-1; LRC-18-175

Journal Information:: Physics of Plasmas, Vol. 25, Issue 7; Related Information: http://dx.doi.org/10.5281/zenodo.1230040; ISSN 1070-664X

Publisher:: American Institute of Physics (AIP)Copyright Statement

Country of Publication:: United States

Language:: English

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Cited by: 3 works

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Analysis Of Equilibrium And Turbulent Fluxes Across The Separatrix In A Gyrokinetic Simulation [Supplementary Data] Charidakos, Ioannis Keramidas; Myra, James; Parker, Scott Zenodo-Supplementary information for journal article at DOI: 10.1063/1.5037723, 15 files (333.7 kB) https://doi.org/10.5281/zenodo.1230040	dataset	April 2018
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Cited By (1)

Analysis Of Equilibrium And Turbulent Fluxes Across The Separatrix In A Gyrokinetic Simulation [Supplementary Data] Charidakos, Ioannis Keramidas; Myra, James; Parker, Scott Zenodo-Supplementary information for journal article at DOI: 10.1063/1.5037723, 15 files (333.7 kB) https://doi.org/10.5281/zenodo.1230040	dataset	April 2018

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70 PLASMA PHYSICS AND FUSION TECHNOLOGY
fusion
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turbulence
gyro-kinetic
simulation

Title: Analysis of equilibrium and turbulent fluxes across the separatrix in a gyrokinetic simulation

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