Effects of medium-Z impurity on H-mode pedestal in DIII-D

The effects of neon level on H-mode pedestal structure at two heating powers in DIII-D lower-single-null discharges are studied. In 3 MW discharges, neon injection resulted in an increase in plasma stored energy and confinement of 30% and 25% respectively. After neon injection, the ELM frequency dropped, the electron pedestal density and pressure increased, and the pedestal temperature slowly decreased. In 6 MW discharges, at the same and even larger neon level, the plasma confinement increased slightly and stored energy gradually increased by up to 15%, while the trend of ELM and pedestal changes was similar to 3 MW discharges. In the neon enhanced confinement phases, the critical pressure gradient along the ballooning boundary of Peeling-Ballooning mode increased. The observed pedestal width will be compared with that predicted by EPED1.0. STRAHL simulations of impurity transport will discussed, as well as the relation between fluctuations and the observed transport changes.