Numerical modeling of MHD/turbulence and their role in setting divertor heat flux width in Wide-Pedestal QH-mode plasmas

Wide-pedestal QH-mode (WPQH), a stationary, quiescent H-mode with pedestal width larger than EPED prediction discovered on DIII-D in recent years is featured with low edge rotation and good H-mode confinement. The MHD and turbulence of WPQH are identified using BOUT++ [1]: a) a low frequency, low-k peeling-ballooning mode that rotates in the ion diamagnetic drift (IDD) direction; b) a higher frequency, intermediate-high k drift-Alfven wave that propagates in the electron diamagnetic drift (EDD) direction; which are consistent with BES/DBS diagnostics. Correlation between amplitude of edge turbulence and the divertor heat flux width is observed experimentally. The role of different modes in setting the divertor heat flux width is studied numerically using BOUT++ 6-field reduced MHD module. By varying the pedestal profiles, it has been found that the IDD mode amplitude increases with a steepened T_i profile and extends radially across the pedestal, broadening the divertor heat flux width. Simulations predict divertor heat flux width increases with the flux-surface-averaged turbulence intensity flux at separatrix. Further, the sheath-limited SOL character of WPQH-Mode is reproduced in the simulation. ([1] Zeyu Li et al 2022 Nucl. Fusion 62 076033)