High ratio of kinetic to magnetic pressure, β, is a signature of good performance and hence desirable in tokamak plasmas. Optimizing plasma operation towards high β requires the integration of sources and transport physics modules in integrated modelling frameworks. Turbulent fluxes, which dominate the transport, are modelled using physics based reduced quasilinear model like trapped gyro Landau fluid (TGLF) (Staebler et al 2007 Phys. Plasmas14 055909). The ability of TGLF to accurately predict turbulent transport at high β is assessed in a comparison against the higher fidelity gyrokinetic code GKW (Peeters et al 2009 Phys. Commun.180 2650–72). The comparison is performed for an idealised case and for a JET-based high β case. The linear response of TGLF is verified and improved to better capture electromagnetic kinetic ballooning modes (KBMs). The quasi-linear fluxes computed with TGLF match within 75% the non-linear heat and particle fluxes computed with GKW for the component carried by electric potential fluctuations. The magnetic flutter component, however, is strongly underestimated. This study indicates that further improvements of the linear solver and refined saturation rules are needed to properly describe high-β electromagnetic turbulence. The general trends and thresholds with respect to the driving gradients are nevertheless captured. With these limitations in mind and using the recommended settings to properly describe KBMs, TGLF can be used in integrated modelling to explore high-β regimes.
This paper evaluates the ability of a reduced turbulence model (TGLF) to accurately predict turbulent transport in high-beta tokamak plasmas. The study compares TGLF results to a more detailed gyrokinetic code (GKW) for both an idealized case and a high-beta JET case. The linear response of TGLF is verified, and improvements are made to better capture electromagnetic kinetic ballooning modes. The study finds that TGLF can capture general trends and thresholds, but further improvements are needed to properly describe high-beta electromagnetic turbulence.