Estimating cross-field particle transport at the outer midplane of TCV by tracking filaments with machine learning

Han, W.; Offeddu, N.; Golfinopoulos, T.; Theiler, C.; Terry, J. L.; Wüthrich, C.; Galassi, D.; Colandrea, C.; Marmar, E. S.

doi:10.1088/1741-4326/acdae5

Estimating cross-field particle transport at the outer midplane of TCV by tracking filaments with machine learning

Journal Article · Fri Jun 09 00:00:00 EDT 2023 · Nuclear Fusion

DOI:https://doi.org/10.1088/1741-4326/acdae5· OSTI ID:1984561

; ; ; ; ; ; ; Colandrea, C.; Marmar, E. S.

Abstract

Cross-field transport of particles in the boundary region of magnetically confined fusion plasmas is dominated by turbulence. Blobs, intermittent turbulent structures with large amplitude and a filamentary shape appearing in the scrape-off layer (SOL), are known from theoretical and experimental studies to be the main contributor to the cross-field particle transport. The dynamics of blobs differs depending on various plasma conditions, including triangularity ( δ ). In this work, we analyze triangularity dependence of the cross-field particle transport at the outer midplane of plasmas with $δ = + 0.38$ , +0.15, −0.14, and −0.26 on the Tokamak à Configuration Variable, using our novel machine learning (ML) blob-tracking approach applied to gas puff imaging data. The cross-field particle flux determined in this way is of the same order as the overall transport inferred from KN1D, GBS, and SOLPS-ITER simulations, suggesting that the blobs identified by the ML blob-tracking account for most of the cross-field particle transport in the SOL. Also, the ML blob-tracking and KN1D show a decrease in the cross-field particle transport as δ becomes more negative. The blob-by-blob analysis of the result from the tracking reveals that the decrease of cross-field particle transport with decreasing δ is accompanied by a decrease in the number of blobs in a fixed time, which tend to have larger area and lower radial speed. Also, the blobs in these plasmas are in the connected sheath regime, and show a velocity scaling consistent with the two-region model.

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Research Organization:: Massachusetts Inst. of Technology (MIT), Cambridge, MA (United States)

Sponsoring Organization:: EUROfusion Consortium; USDOE; USDOE Office of Science (SC), Fusion Energy Sciences (FES)

Contributing Organization:: TCV Team

Grant/Contract Number:: SC0014264; SC0020327

OSTI ID:: 1984561

Alternate ID(s):: OSTI ID: 2420342
OSTI ID: 1983494

Journal Information:: Nuclear Fusion, Journal Name: Nuclear Fusion Journal Issue: 7 Vol. 63; ISSN 0029-5515

Publisher:: IOP PublishingCopyright Statement

Country of Publication:: IAEA

Language:: English

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