Spectroscopic study of nonthermal plasmas

The line ratio of a dielectronic satellite to the main optically allowed line in Fe xxv has been measured in plasma discharges with a non-Maxwellian electron distribution such as those produced in tokamaks at low electron density or during heating experiments by means of Landau damping of electromagnetic waves launched into the plasma. The effect of nonthermal electrons has been clearly established in a series of experiments performed in the Frascati tokamak FT and the expressions for line intensities in these plasma conditions have been worked out. A data-analysis procedure is also presented which can give quantitative information about the nonthermal-electron content in the plasma.