Assessment of tungsten impurity concentration in the all-metallic environment of the WEST during experiments based on integrated multi-diagnostic analysis.

WEST is an actively cooled, long-pulse tokamak with nearly all plasma-facing components (PFC) made of tungsten (W). One of the aims of WEST is to study plasma operations with W PFCs in preparation for long-pulse operations on W divertor devices like ITER. For long-pulse operation, the W impurity content and transport to the core plasma are critical concerns that require further measurement and interpretation in order to improve plasma performance and PFC durability. This work details the overall impurity influxes in WEST by characterizing sources at the antennas and at the divertor during a series of discharges in which the Lower Hybrid (LH) injected power was incrementally increased during the C4 (2018) and C5 (2019) experimental campaigns. Visible spectroscopy was utilized to measure the spectral radiances generated by fuel particles (deuterium) and impurities (e.g., W, oxygen (O), boron (B)) at both locations. The needed SOL plasma conditions (Ne, Te) to evaluate the S/XB coefficients required to estimate the impurity fluxes obtained with a collisional-radiative model (ColRadPy) are measured at the divertor target with Flush Langmuir probes and near the OMP using reciprocating Langmuir probes. The array of edge diagnostics have identified an increase of O and W impurities during the C5 campaign, which is likely induced by the introduction of boron nitride (BN) limiters. The intensity of neutral W emission (W-I) near the divertor relative to the antenna region for the two campaigns will also be discussed with regard to identifying the dominant sources of impurity production.