Multi-reservoir particle balance analysis of RMP discharges at MAST

A marked decrease in particle confinement time with a coinciding increase of neutral fueling to the plasma was found in L- and H-mode discharges at MAST when resonant magnetic perturbations (RMPs) were applied, which together indicate that transport is enhanced. To investigate this result that came from a 0-D particle balance, a multi-pronged approach was developed using experimental data and plasma modeling to understand the effect of neutral fueling and exhaust on the plasma pump-out. A time dependent multi-reservoir particle balance model with atomic, molecular, plasma, and wall reservoirs was developed to resolve further the specific role neutral particles play on fueling the plasma during pump-out. EMC3-EIRENE simulations estimate that molecular dissociation makes up approximately one quarter of ions fueling the plasma, which is reproduced in the multi-reservoir model along with a slight decrease of that fraction when RMPs are applied. The result was shown to be sensitive to the absorption mechanism of atoms vs. molecules at the wall, which implies a necessary enhancement to the multi-reservoir model.