Reduced models for ETG transport in the tokamak pedestal

D. R. Hatch, C. Michoski, D. Kuang, B. Chapman-Oplopoiou, M. Curie, M. Halfmoon, E. Hassan, M. Kotschenreuther, S. M. Mahajan, G. Merlo, M. J. Pueschel, J. Walker, C. D. Stephens

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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 pedestals in a broad range of experimental scenarios. The simulation data have 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 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.

Original languageEnglish
Article number062501
JournalPhysics of Plasmas
Volume29
Issue number6
DOIs
StatePublished - Jun 1 2022

Funding

We would like to thank several collaborators in the Partnership for Multiscale Gyrokinetic Turbulence (MGK) and Anthony Field for useful discussions. This research used resources of the National Energy Research Scientific Computing Center, a DOE Office of Science User Facility, and the Texas Advanced Computing Center (TACC) at The University of Texas at Austin. This work was supported by U.S. DOE under Contract No. DE-FG02-04ER54742, and the U.S. DOE Office of Fusion Energy Sciences Scientific Discovery through Advanced Computing (SciDAC) program under Award No. DE-SC0018429. This work has been carried out within the framework of the EUROfusion Consortium, funded by the European Union via the Euratom Research and Training Programme (Grant Agreement No. 101052200 EUROfusion). Views and opinions expressed are, however, those of the author(s) only and do not necessarily reflect those of the European Union or the European Commission. Neither the European Union nor the European Commission can be held responsible for them.

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