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Article Dans Une Revue Plasma Physics and Controlled Fusion Année : 2024

Stability analysis of WEST L-mode discharges with improved confinement from boron powder injection

Résumé

WEST L-mode plasmas with dominant electron heating and no core torque source have observed improvements in confinement during boron (B) powder injection. These results are reminiscent of previous powder injection experiments on other devices and gaseous impurity seeding experiments on WEST. During powder injection, the stored energy increased up to 25% due to enhanced ion and electron heat and particle confinement. The improvements in confinement were not indicative of an L-H transition. To identify the dominant mechanisms and the causality chain behind these improvements in confinement, we employ interpretative modelling using METIS, predictive integrated modelling using a high-fidelity plasma simulator (HFPS), and stand-alone gyrokinetic simulations using QuaLiKiz. Interpretative modelling with METIS allowed for the estimation of missing data while maintaining good overall consistency with experiment. These results provided the initial conditions for fully predictive flux driven simulations using the HFPS. From these simulations, quasi-linear gyrokinetic analysis was performed at ρ=0.5 and ρ=0.65. Collisionality was found to be a strong candidate for turbulence suppression at ρ=0.5, while a combination of collisionality and the $T_e$ /$T_i$ ratio was found to be the likely mechanism at ρ=0.65. The results additionally suggested that increased $Z_{eff}$ (through main ion dilution) could play a role in the improved confinement, but this could not be confirmed due to a lack of experimental measurements. The modelling framework established here can now be used to evaluate and exploit a variety of future powder injection experiments.
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Dates et versions

cea-04496850 , version 1 (08-03-2024)

Identifiants

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Grant Bodner, Clarisse Bourdelle, Pierre Manas, Alberto Gallo, Kirill Afonin, et al.. Stability analysis of WEST L-mode discharges with improved confinement from boron powder injection. Plasma Physics and Controlled Fusion, In press, ⟨10.1088/1361-6587/ad2c29⟩. ⟨cea-04496850⟩
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