Description
Multi-energy soft x-ray pinhole cameras have been designed, constructed, calibrated, and operated on MST, Alcator C-Mod, and more recently on TCV and WEST to measure spatially and spectrally resolved plasma emission across multiple energy bands. Here we present a new methodology to estimate the local plasma effective charge from tungsten-resolved soft x-ray measurements on WEST. Two complementary approaches are developed. The first exploits spatially, temporally, and spectrally resolved measurements in the 2-6 keV range, where tungsten line emission dominates. By combining tungsten line features with emission attributed to nitrogen (used as a proxy for low-Z fully stripped ions), we infer tungsten and light impurity concentrations, from which deuterium density concentration and Zeff can be deduced. The second method uses photon-counting measurements of the line-free continuum in several energy bands between 11 and 18 keV. The analysis leverages a well-characterized detector responsivity, modeled by a complementary error function, and interprets differential multi-energy measurements between adjacent energy thresholds through the probability density function of a Gaussian distribution. This framework enables robust extraction of continuum emissivity and impurity content. Implementation of these techniques is ongoing on the WEST tokamak, with the goal of providing real-time estimates of Prad and Zeff during both short- and long-pulse operation in a challenging W-environment.