Modeling electron temperature profiles in the pedestal with simple formulas for ETG transport

Hatch, D. R.; Kotschenreuther, M. T.; Li, P. -Y.; Chapman-Oplopoiou, B.; Parisi, J.; Mahajan, S. M.; Groebner, R.

doi:10.1088/1741-4326/ad3972

Title: Modeling electron temperature profiles in the pedestal with simple formulas for ETG transport

Journal Article · 21 April 2024 · Nuclear Fusion

DOI: https://doi.org/10.1088/1741-4326/ad3972 · OSTI ID:2339899

; Kotschenreuther, M. T.;

;

; Mahajan, S. M.;

Abstract This paper reports on the refinement (building on (Hatch D.R. et al 2022 Phys. Plasmas 29 062501)) and application of simple formulas for electron heat transport from electron temperature gradient (ETG) driven turbulence in the pedestal. The formulas are improved by (1) improving the parameterization for certain key parameters and (2) carefully accounting for the impact of geometry and shaping in the underlying gyrokinetic simulation database. Comparisons with nonlinear gyrokinetic simulations of ETG transport in the MAST pedestal demonstrate the model’s applicability to spherical tokamaks in addition to standard aspect ratio tokamaks. We identify bounds for model applicability: the model is accurate in the steep gradient region, where the ETG turbulence is largely slab-like, but accuracy decreases as the temperature gradient becomes weaker in the pedestal top. We use the formula to model the electron temperature profile in the pedestal for four experimental scenarios while extensively varying input parameters to represent uncertainties. In all cases, the predicted electron temperature profile exhibits extreme sensitivity to separatrix temperature and density, which has implications for core-edge integration. The model reproduces the electron temperature profile for high $η_{e} = L_{n e} / L_{T e}$ scenarios but not for low η _e scenarios in which microtearing modes (MTMs) have been identified. We develop a proof-of-concept model for MTM transport and explore the relative roles of ETG and MTM in setting the electron temperature profile.

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Research Organization:: General Atomics, San Diego, CA (United States); Princeton Plasma Physics Laboratory (PPPL), Princeton, NJ (United States)

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

Grant/Contract Number:: AC02-09CH11466; FC02-04ER54698; FG02-04ER54742; SC0018429; SC0022164

OSTI ID:: 2339899

Journal Information:: Nuclear Fusion, Journal Name: Nuclear Fusion Journal Issue: 6 Vol. 64; ISSN 0029-5515

Publisher:: IOP PublishingCopyright Statement

Country of Publication:: IAEA

Language:: English

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Title: Modeling electron temperature profiles in the pedestal with simple formulas for ETG transport

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