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Journal Articles Nuclear Fusion Year : 2022

Transport barrier in 5D gyrokinetic flux-driven simulations

G. Lo-Cascio
Etienne Gravier
M. Lesur
Y. Sarazin
X. Garbet
L. Vermare
K. Lim
A. Guillevic
V. Grandgirard


Abstract Two ways for producing a transport barrier through strong shear of the E × B poloidal flow have been investigated using GYSELA gyrokinetic simulations in a flux-driven regime. The first one uses an external poloidal momentum (i.e. vorticity) source that locally polarizes the plasma, and the second one enforces a locally steep density profile that also stabilizes the ion temperature gradient (ITG) instability modes linearly. Both cases show a very low local turbulent heat diffusivity coefficient χ T turb and a slight increase in core pressure when a threshold of ω E × B ≈ γ ¯ lin (respectively the E × B shear rate and average linear growth rate of ITG) is reached, validating previous numerical results. This pressure increase and χ T turb quench are the signs of a transport barrier formation. This behaviour is the result of a reduced turbulence intensity which strongly correlates with the shearing of turbulent structures as evidenced by a reduction of the auto-correlation length of potential fluctuations as well as an intensity reduction of the k θ spectrum. Moreover, a small shift towards smaller poloidal wavenumber is observed in the vorticity source region which could be linked to a tilt of the turbulent structures in the poloidal direction.
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Dates and versions

hal-03838047 , version 1 (08-02-2023)



G. Lo-Cascio, Etienne Gravier, T. Réveillé, M. Lesur, Y. Sarazin, et al.. Transport barrier in 5D gyrokinetic flux-driven simulations. Nuclear Fusion, 2022, 62 (12), pp.126026. ⟨10.1088/1741-4326/ac945d⟩. ⟨hal-03838047⟩
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