A theory-based transport model with comprehensive physics

Abstract

A new theory-based transport model with comprehensive physics (trapping, general toroidal geometry, fully electromagnetic, electron-ion collisions, impurity ions) has been developed. The core of the model is the new trapped-gyro-Landau-fluid (TGLF) equations, which provide a fast and accurate approximation to the linear eigenmodes for gyrokinetic drift-wave instabilities (trapped ion and electron modes, ion and electron temperature gradient modes, and kinetic ballooning modes). The new TGLF transport model is more accurate, and has an extended range of validity, compared to its predecessor GLF23. The TGLF model unifies trapped and passing particles in a single set of gyro-Landau-fluid equations. A model for the averaging of the Landau resonance by the trapped particles makes the equations work seamlessly over the whole drift-wave wave-number range from trapped ion modes to electron temperature gradient modes. A fast eigenmode solution method enables unrestricted magnetic geometry. The transport model uses the TGLF eigenmodes to compute quasilinear fluxes of energy and particles. A model for the saturated intensity of the turbulence completes the flux calculation. The intensity model is constructed to fit a large set of nonlinear gyrokinetic turbulence simulations with kinetic electrons. The TGLF model is valid in new physical regimes that GLF23 was not. These include the low aspect ratio spherical torus, which has both a high trapped fraction and strong shaping of magnetic flux surfaces. The TGLF model is also valid close to the magnetic separatrix so the transport physics of the H-mode pedestal region can be explored.