Understanding the poloidal distribution of W sourcing by light impurities and heating method in WEST*

Recent experiments were performed in lower-single-null discharges with dominant RF heating up to 5 MW to evaluate in-situ tungsten (W) erosion measurements in an effort to determine the main W sourcing locations within the vessel. The distribution of W sources is seen to change with the increased RF heating, going from dominate gross erosion at either strikepoint (SP) location to a more balanced source distribution between each SP. The main chamber limiter gross erosion is seen to increase with the SOL electron temperature but is ~10x less than the divertor gross erosion, although the penetration probability across the separatrix is higher from this location than from the divertor target locations and potentially has a larger impact on core contamination. Neutral W spectroscopy using W-I emission measurements are taken from multiple poloidal locations to characterize the gross erosion rate around the vessel, and incident particle fluxes are characterized by Langmuir probes, both embedded and plunged, and spectroscopy methods. Constrained by these measurements, SolEdge-EIRENE shows, taking oxygen as a proxy light impurity, consistent poloidal erosion patterns to those measured. These simulations suggest low fractions (~few % of the background electron density) of oxygen are the main erosion drivers throughout the vessel and that the charge state distribution of oxygen has significant impact on the erosion rate.