Effects of 3-D magnetic fields on neutral fueling and exhaust at MAST*

The application of resonant magnetic perturbations (RMPs) at MAST has been shown to cause density pump-out during discharges that have a particular MHD response. This occurs in both L-mode and H-mode discharges. An analysis of the changes in fueling and exhaust show that RMPs cause an increase in total fueling to the plasma, from D_α emission measurements, but also a significant drop in particle confinement time, from a 0-D single reservoir particle balance of the main ion species, such that there is a net particle pump-out. In order to better understand the impact of neutrals to this pump-out, a 1-D global particle balance with reservoirs for both atomic and molecular deuterium is used. This simple model can accurately reproduce experimental conditions and can also be used to explore the parameters describing the plasma-surface interactions and fueling fraction of ionized particles to the core and how those terms change with the RMP application. New Wisconsin In-Situ Penning (WISP) gauges are being installed on MAST-U to aid in measurement of neutral pressure in the vessel and divertor regions for future particle balance analysis with the capability to measure helium and other impurity concentrations.