Strong gradient effects on neoclassical electron transport and the bootstrap current in large aspect ratio tokamaks

Trinczek, Silvia; Parra, Felix I.; Catto, Peter J.

doi:10.1017/S0022377825100421

Strong gradient effects on neoclassical electron transport and the bootstrap current in large aspect ratio tokamaks

Journal Article · Thu Jul 10 00:00:00 EDT 2025 · Journal of Plasma Physics

DOI:https://doi.org/10.1017/S0022377825100421· OSTI ID:3000734

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Princeton Plasma Physics Laboratory (PPPL), Princeton, NJ (United States)
Massachusetts Inst. of Technology (MIT), Cambridge, MA (United States)

Standard approaches to neoclassical theory do not extend into regions of strong gradients in tokamaks such as the pedestal and internal transport barriers. Here, we calculate the modifications to neoclassical electron physics inside strong gradient regions of large aspect ratio tokamaks in the banana regime. We show that these modifications are due to the different ion flow and the strong poloidal variation of the potential. We also provide a physical interpretation of the mechanisms that drive poloidal asymmetries and hence a poloidal electric field. We apply our model to two specific example cases of pedestal profiles, calculating the neoclassical electron flux and the bootstrap current. We find that, depending on the ion flow, weak gradient neoclassical theory overestimates or underestimates the neoclassical electron transport and the bootstrap current in regions with strong gradients. We show that the determination of the mean parallel flow is more complex than in weak gradient neoclassical theory. For vanishing turbulence, we can determine the radial electric field for a given flow profile in the pedestal.

View Accepted Manuscript (DOE)

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

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

Grant/Contract Number:: FG02-91ER54109; AC02-09CH11466

OSTI ID:: 3000734

Alternate ID(s):: OSTI ID: 2586607

Journal Information:: Journal of Plasma Physics, Journal Name: Journal of Plasma Physics Journal Issue: 4 Vol. 91; ISSN 0022-3778; ISSN 1469-7807

Publisher:: Cambridge University Press (CUP)Copyright Statement

Country of Publication:: United States

Language:: English

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