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Poster Communications Year : 2022

Simulations of impurity transport with TERESA and GYSELA codes

Abstract

We analyze properties of the radial turbulent transport of light to heavy impurities based on global gyrokinetic simulations. We describe how transport depends on impurity concentration, charge, mass, gradients, poloidal asymmetry, rotation, and on the nature of the underlying dominant instability – either Ion Temperature Gradient (ITG) or Trapped Electron Mode (TEM). We used the GYSELA-X code for ITG simulations with a realistic collision operator [1] and improved boundary conditions, and TERESA code for collisionless TEM simulations with impurities [2]. GYSELA-X describes the 5D distribution of gyrocenters, while TERESA describes the 4D distribution of gyro-bounce-centers (banana centers). TERESA simulations indicate that the validity of the usual passive treatment of impurities is limited to a concentration C of W40+ tungsten below 2x10-4. We describe the impact of C on linear growth rate, turbulence intensity, and impurity density flux. A transition centered around C Z^2 = 1.1 is significantly steeper for the flux. This is due to a mechanism of phase-synchronization between impurity density and potential fluctuations, which quenches impurity transport [3]. Treating trace impurities self-consistently, we observe how diffusive impurity transport increases (resp. decreases) with charge number Z for TEM (TIM) turbulence. Mass number is less impacting [4]. The direction of thermo-diffusion depends on the nature of turbulence as expected from quasilinear theory, and on the impurity temperature profile. Curvature pinch is inward except in some negative magnetic shear cases. GYSELA-X simulations confirm that turbulent (resp. neoclassical) transport dominates for light (heavy) impurity leading to hollow (peaked) density profile. Pfirsch-Schlüter flux dominates for tungsten. Behavior of intermediate-mass impurity (argon) is more subtle, but banana-plateau flux dominates in the core. Turbulence generates 20% up-down asymmetry for high-Z impurities, impacting neoclassical transport [5]. Toroidal rotation increases in-out asymmetry and central tungsten accumulation. [1] D. Estève, et al., Nucl. Fusion 58 (2018) 036013 [2] M. Idouakass et al., Phys. Plasmas 25 (2018) 062307 [3] M. Lesur et al., Nucl. Fusion 60 (2020) 036016 [4] E. Gravier et al., Phys. Plasmas 26 (2019) 082306 [5] K. Lim et al., Nucl. Fusion 61 (2021) 046037 [6] C. Angioni et al., Nucl. Fusion 52 (2012) 114003
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Dates and versions

hal-04595305 , version 1 (03-06-2024)

Identifiers

  • HAL Id : hal-04595305 , version 1

Cite

Maxime Lesur, Kyungtak Lim, Lo-Cascio G., Garbet X., Sarazin Y., et al.. Simulations of impurity transport with TERESA and GYSELA codes. US-EU joint Transport Taskforce Workshop, Apr 2022, Santa Rosa, United States. 2022. ⟨hal-04595305⟩
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