Determining neutral fueling response to RMPs in MAST using a multi-reservoir particle balance model and EMC3 EIRENE

Abstract

The application of certain configurations of resonant magnetic perturbations (RMPs) has been shown to cause a plasma pump-out in both L- and H-mode discharges at MAST. In this paper we discuss the impact of neutral fueling on this density reduction. The neutral fueling and average particle confinement time ${\tau }_p$ of the main ion species were calculated using a 0-D particle balance analysis. When the RMPs were applied, it was found that there was an increase in ionizations and a 15$\%$ reduction in ${\tau }_p$ for L-mode discharges and a similar result for inter-ELM (edge localized modes) periods of H-mode discharges. A time-dependent global multi-reservoir particle balance (MRPB) was developed, which included atomic and molecular reservoirs, to further investigate the role neutrals had on the density change. We discuss how this model was able to accurately reproduce the experimentally measured density reduction and ionization increase due to either a reduction in ${\tau }_p$ or a reduction in particle fueling efficiency. Results from EMC3-EIRENE modeling indicate this change could be attributed to neutral particle fueling occurring in locations with now-opened field lines due to the chaotic edge-region from RMP applications.

26 pages, 15 figures, submitted to Nuclear Fusion