Edge power balance and TGLF/TGYRO-predicted quasilinear thermal fluxes in ITER-Similar-Shape DIII-D Plasmas near the L-H Transition

Recent experiments in ITER Similar Shape (ISS), low collisionality, low torque hydrogen plasmas near sawtooth-triggered L-H transitions have shown that the edge ion heat flux calculated by TRANSP is increased by a factor of ~3 compared to reference deuterium ISS plasmas, while edge electron heat flux is largely unchanged. This observation strengthens previous claims that the ion heat flux plays a dominant role in L-H transition physics [1]. Validation of L-mode edge thermal fluxes predicted by TGLF/TGYRO quasilinear gyrofluid simulations have identified dominant trapped electron mode (TEM) and electron temperature gradient mode (ETG) turbulence in both the deuterium and hydrogen plasmas at similar scale lengths. Additionally, TGLF has reproduced the experimental isotopic dependence on edge ion heat flux. TGYRO quasilinear simulations indicate that the predicted heat fluxes match the results from power balance analysis for both H and D plasmas using TGLF saturation rule 1 (a saturation model based on a Zonal flow mixing [2]).

[1] F. Ryter et al., Nucl. Fusion 58 014007 (2016).

[2] G. Staebler et al., Physics of Plasmas 23, 062518 (2016).