Efficient modelling of tungsten x-ray and EUV emission under ITER plasma conditions

Abstract Synthetic line-emission spectra of tungsten ions in the x-ray (1–10 Å) and extreme-ultraviolet (10–140 Å) ranges under ITER conditions have been modelled for the charge-state groups W 44+ –W 47+ and W 62+ –W 65+ , covering both outer and core plasma regions. Atomic structure and electron-impact excitation data have been calculated using two fully independent, fully relativistic suites, each treating excitation within the distorted-wave approximation. The close agreement between these separate datasets provides a strong internal consistency check in spectral regions where experimental validation is often hindered by line blending and background radiation. Photon emissivity coefficients, local emissivity profiles, and synthetic spectra have been obtained by coupling these atomic data to collisional-radiative modelling and to realistic ITER temperature and density profiles. Line-of-sight integrated spectra have then been compared with reduced approaches that evaluate each charge state at its temperature of maximum fractional abundance, and with simplified fixed-temperature treatments. The resulting spectra show that the reduced-temperature models reproduce the fully integrated spectra with high accuracy, while fixed-temperature approaches capture the main features with reasonable fidelity. These results indicate that computationally efficient reduced-temperature methods can provide reliable forward predictions for diagnostic design, line identification, and the interpretation of future ITER measurements.