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Title: Multispecies density peaking in gyrokinetic turbulence simulations of low collisionality Alcator C-Mod plasmas

Journal Article · · Physics of Plasmas
DOI:https://doi.org/10.1063/1.4922069· OSTI ID:22410435
; ;  [1]; ; ; ;  [2];  [2];  [2];  [2]; ;  [3]
  1. Princeton Plasma Physics Laboratory, P.O. Box 451, Princeton, New Jersey 08543 (United States)
  2. MIT Plasma Science and Fusion Center, 175 Albany St., Cambridge, Massachusetts 02139 (United States)
  3. General Atomics, P.O. Box 85608, San Diego, California 92186-5608 (United States)

Peaked density profiles in low-collisionality AUG and JET H-mode plasmas are probably caused by a turbulently driven particle pinch, and Alcator C-Mod experiments confirmed that collisionality is a critical parameter. Density peaking in reactors could produce a number of important effects, some beneficial, such as enhanced fusion power and transport of fuel ions from the edge to the core, while others are undesirable, such as lower beta limits, reduced radiation from the plasma edge, and consequently higher divertor heat loads. Fundamental understanding of the pinch will enable planning to optimize these impacts. We show that density peaking is predicted by nonlinear gyrokinetic turbulence simulations based on measured profile data from low collisionality H-mode plasma in Alcator C-Mod. Multiple ion species are included to determine whether hydrogenic density peaking has an isotope dependence or is influenced by typical levels of low-Z impurities, and whether impurity density peaking depends on the species. We find that the deuterium density profile is slightly more peaked than that of hydrogen, and that experimentally relevant levels of boron have no appreciable effect on hydrogenic density peaking. The ratio of density at r/a = 0.44 to that at r/a = 0.74 is 1.2 for the majority D and minority H ions (and for electrons), and increases with impurity Z: 1.1 for helium, 1.15 for boron, 1.3 for neon, 1.4 for argon, and 1.5 for molybdenum. The ion temperature profile is varied to match better the predicted heat flux with the experimental transport analysis, but the resulting factor of two change in heat transport has only a weak effect on the predicted density peaking.

OSTI ID:
22410435
Journal Information:
Physics of Plasmas, Vol. 22, Issue 6; Other Information: (c) 2015 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA); ISSN 1070-664X
Country of Publication:
United States
Language:
English

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Multi-scale gyrokinetic simulations of an Alcator C-Mod, ELM-y H-mode plasma journal November 2017
A new mechanism for increasing density peaking in tokamaks: improvement of the inward particle pinch with edge E × B shearing journal August 2019
Global gyrokinetic simulations of intrinsic rotation in ASDEX Upgrade Ohmic L-mode plasmas journal March 2018
Fast H isotope and impurity mixing in ion-temperature-gradient turbulence journal July 2018
Understanding helium transport: experimental and theoretical investigations of low-Z impurity transport at ASDEX Upgrade journal March 2019
Control of the hydrogen:deuterium isotope mixture using pellets in JET journal September 2019