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

Bodner, G.; Bourdelle, C.; Manas, P.; Gallo, A.; Afonin, K.; Diallo, A.; Lunsford, R.; Moreau, Ph.; Nagy, A.; Clairet, F.; Gil, C.; Tsitrone, E.; Vermare, L.

doi:10.1088/1361-6587/ad2c29

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

Journal Article · Tue Mar 12 00:00:00 EDT 2024 · Plasma Physics and Controlled Fusion

DOI:https://doi.org/10.1088/1361-6587/ad2c29· OSTI ID:2426347

^[1]; ^[2]; Manas, P. ^[2]; ^[2]; ^[2]; ^[1]; ^[1]; Moreau, Ph. ^[2]; Nagy, A. ^[1]; Clairet, F. ^[2]; Gil, C. ^[2]; Tsitrone, E. ^[2]; Vermare, L. ^[3]

Princeton Plasma Physics Laboratory (PPPL), Princeton, NJ (United States)
CEA, IRFM, Saint Paul Lez Durance (France)
École Polytechnique, Paris (France)

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 modeling using METIS, predictive integrated modeling using a high-fidelity plasma simulator (HFPS), and stand-alone gyrokinetic simulations using quasi-linear gyrokinetic code. Interpretative modeling 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 the turbulence suppression mechanism 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 modeling framework established here can now be used to evaluate and exploit a variety of future powder injection experiments.

View Accepted Manuscript (DOE)

Research Organization:: Princeton Plasma Physics Laboratory (PPPL), Princeton, NJ (United States)

Sponsoring Organization:: USDOE Office of Science (SC), Biological and Environmental Research (BER). Earth & Environmental Systems Science (EESS)

Contributing Organization:: The WEST Team

Grant/Contract Number:: AC02-09CH11466

OSTI ID:: 2426347

Journal Information:: Plasma Physics and Controlled Fusion, Journal Name: Plasma Physics and Controlled Fusion Journal Issue: 4 Vol. 66; ISSN 0741-3335

Publisher:: IOP ScienceCopyright Statement

Country of Publication:: United States

Language:: English

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