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

Nuclear Fushion

article

W. Han¹  N. Offeddu²  T. Golfinopoulos¹  C. Theiler²  J.L. Terry¹  C. Wüthrich²  D. Galassi²  C. Colandrea²  E.S. Marmar¹  the TCV Team² 

[1] MIT Plasma Science and Fusion Center;École Polytechnique Fédérale de Lausanne ,(EPFL), Swiss Plasma Center

关键词: negative triangularity;    edge/SOL turbulence;    machine learning;    gas puff imaging;    particle transport;    tokamak;   

DOI  :  10.1088/1741-4326/acdae5

来源: Institute of Physics Publishing Ltd.

【 摘 要 】

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 delta = +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 asδbecomes more negative. The blob-by-blob analysis of the result from the tracking reveals that the decrease of cross-field particle transport with decreasingδis 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.

【 授权许可】

Unknown