2024/04/02 by D.R. Hatch, D. R. Hatch, M.T. Kotschenreuther +10 · 19 citations
Materials Science · Physics and Astronomy · #Computational physics #Electron #Electron temperature #Fusion materials and technologies #Ionosphere and magnetosphere dynamics #Magnetic confinement fusion research #Materials science #Meteorology #Nuclear physics #Pedestal #Physics #Plasma #Temperature gradient #Thermodynamics #Tokamak #Turbulence
paper · pdf · doi:10.1088/1741-4326/ad3972
published in Nuclear Fusion 64(6), 066007 (IOP Publishing)
openalex publication_date 2024/04/02 · openalex created_date 2025/10/10 · openalex updated_date 2026/08/01
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 <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mrow> <mml:msub> <mml:mi>η</mml:mi> <mml:mi>e</mml:mi> </mml:msub> <mml:mo>=</mml:mo> <mml:msub> <mml:mi>L</mml:mi> <mml:mrow> <mml:mi>n</mml:mi> <mml:mi>e</mml:mi> </mml:mrow> </mml:msub> <mml:mrow> <mml:mo>/</mml:mo> </mml:mrow> <mml:msub> <mml:mi>L</mml:mi> <mml:mrow> <mml:mi>T</mml:mi> <mml:mi>e</mml:mi> </mml:mrow> </mml:msub> </mml:mrow> </mml:math> 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.