The effect of inner-shell ionization on intensities of lines from Mg I-like ions in Tokamak plasmas

Tokamak spectra of the Mg I-like ions of high-Z elements (Z = 21-24), have consistently shown that the 3s²¹S₀-3s3p³P₁ intercombination line is brighter than expected relative to the 3s²¹S₀-3s3p³P₁ resonance line. The 3s3p³P₂-3s3d³D₃ transition is also found to be anomalously strong. The results of modeling measured relative intensities of Mg I-like selenium (Se XXIII) lines from Princeton large torus (PLT) tokamak spectra are presented. The observations cannot be explained by a level population model including only electron collisions and radiative decay between the levels of the Mg I-like ion. Agreement with the data is found when direct population of the 3s3p levels by inner-shell ionization of the Al I-like ion is included; indicating that these processes are important for Mg I-like ions at the temperatures and densities of tokamak plasmas.