Drift direction dependence of main chamber ionization source asymmetries in DIII-D H-mode plasmas

Understanding poloidal asymmetries in main chamber fueling is essential to characterize the balance of diffusive and convective particle transport, and the role of neutrals in the density pedestal formation. Strong in-out asymmetries of the main chamber ionization source have previously been shown on DIII-D. In this contribution, we investigate DIII-D ELMy H-mode plasmas with changing magnetic configurations varied from lower-single-null (LSN) through double-null (DN) to upper-single-null (USN) for both directions of the toroidal magnetic field. The main chamber ionization rate on the high-field-side (HFS) is an order of magnitude larger than on the low-field-side (LFS) with favorable B × ∇B drift direction, while fueling is more balanced with unfavorable drift. As the configuration changes from lower biased DN (favorable) to upper biased DN (unfavorable), there is a significant reduction in ionization rate at the HFS, indicating the reduction in ion flux arriving at the inner target as a result of the changing magnetic topology. In LSN, we observe large variations in the main chamber ionization source during the inter-ELM period which is currently being investigated. This includes characterizing the variation in the divertor condition during the inter-ELM period and its effect on pedestal fueling.