Studies of ETG Transport on NSTX Plasmas with Gyrokinetics and Reduced Transport Models

C.F. Clauser, T. Rafiq, E. Schuster, C. Wilson, W. Guttenfelder, J. Parisi, G. Avdeeva

29th IAEA Fusion Energy Conference

London, UK, October 16-21, 2023

Abstract

A series of NSTX and NSTX-U plasmas are analysed to investigate the anomalous electron thermal transport caused by electron temperature gradient (ETG) modes. The high-fidelity gyrokinetic code CGYRO is employed to carry out extensive linear and nonlinear ETG simulations. Linear gyrokinetic simulations are performed to determine ETG thresholds in different discharges, and they are compared with the simple scaling formula derived for conventional tokamaks. Results are also compared with reduced models to better understand their applicability in spherical tokamaks as well as in future reactor conditions. Nonlinear gyrokinetic simulations are conducted for selected cases to calculate electron thermal transport and compare the results with those of ETG modes in the Multi-Mode Model (MMM) and the Trapped-Gyro-Landau-Fluid (TGLF) reduced model codes.