Impact Of The Plasma Configuration On H-mode Pedestal Ionization Source And ELM Dynamics In DIII-D

We present a study of the H-mode pedestal profile structure, edge localized mode (ELM) behavior and ionization source for varied plasma configurations (single null with open and more closed divertor as well as double null (DN)) and both directions of the ion B×∇B drift. The ELM behavior and the poloidal ionization source distribution show strong variations with changes in the divertor configuration. In DN shapes, the pedestal structure is most stable to peeling-ballooning modes due to plasma shaping and it exhibits the lowest ELM repetition frequency. When the ion B × ∇B drift direction is pointing away from the X-point, the ELM frequency is at least by a factor of two higher than for cases with ion B × ∇B drift direction pointing towards the X-point. The pedestal ionization source in the main chamber can exhibit significant poloidal asymmetries with one order of magnitude larger ionization source on high field side in comparison to the low field side. Our observations point towards modifications of the edge profile peeling-ballooning stability and dynamics through variations of the edge density, which are related to the variation in pedestal particle fueling.