Poloidal dependence of pellet ELM triggering in low-collisionality discharges

Previous linear M3D-C1 simulations found a strong poloidal dependence of the critical pellet size threshold for ELM triggering in low-collisionality discharges in DIII-D. However, such linear simulations do not include pellet ablation physics or time evolution of density and temperature. A new scheme of 2D nonlinear simulations, coupled with linear stability analysis at various steps throughout the nonlinear time evolution, was developed to include such physics and improve on the previous linear results. These new nonlinear-to-linear simulations confirm previous findings. Especially, contrary to experimental observations in JET for higher collisionality pedestals, the simulations find the outboard midplane to be the location with by far the lowest threshold and therefore most effective triggering in these DIII-D discharges.