Reduced models for ETG transport in the pedestal

Abstract

This paper reports on the development of reduced models for electron temperature gradient (ETG) driven transport in the pedestal. Model development is enabled by a set of 61 nonlinear gyrokinetic simulations with input parameters taken from the pedestals in a broad range of experimental scenarios. The simulation data has been consolidated in a new database for gyrokinetic simulation data, the Multiscale Gyrokinetic Database (MGKDB), facilitating the analysis. The modeling approach may be considered a generalization of the standard quasilinear mixing length procedure. The parameter η, the ratio of the density to temperature gradient scale length, emerges as the key parameter for formulating an effective saturation rule. With a single order-unity fitting coefficient, the model achieves an RMS error of 15%. A similar model for ETG particle flux is also described. We also present simple algebraic expressions for the transport informed by an algorithm for symbolic regression.

Three-dimensional inhomogeneity of electron-temperature-gradient turbulence in the edge of tokamak plasmas

“…We have shown that retaining k y ρ i ∼ 1 ETG modes is crucial to capture correctly the k y ρ e ∼ 1 electron heat flux. This is relevant for tokamak turbulence modeling [52,[110][111][112][113][114][115] that aims to predict experimental fluxes accurately. While this result is not the first to show k y ρ i ∼ 1 turbulence suppressing k y ρ e ∼ 1 turbulence [21,23,24,116], it is the first to show ETG turbulence at k y ρ i ∼ 1 suppressing ETG turbulence and transport at k y ρ e ∼ 1.…”

Three-Dimensional Inhomogeneity of Electron-Temperature-Gradient Turbulence in the Edge of Tokamak Plasmas

“…We have shown that retaining k y ρ i ∼ 1 ETG modes is crucial to capture correctly the k y ρ e ∼ 1 electron heat flux. This is relevant for tokamak turbulence modeling [52,[106][107][108][109][110][111] that aims to predict experimental fluxes accurately. While this result is not the first to show k y ρ i ∼ 1 turbulence suppressing k y ρ e ∼ 1 turbulence [21,23,24,112], it is the first to show ETG turbulence at k y ρ i ∼ 1 suppressing ETG turbulence and transport at k y ρ e ∼ 1.…”