Line radiation in the visible and in the ultraviolet in TFR tokamak plasmas

Abstract

Line radiation in the vísible and ultraviolet (100–1300 Å) spectral regions has been studied on TFR for a 140-kA, 26-kG plasma. The emission is integrated along the line of sight, except for neutral-deuterium visible radiation, which has been spatially resolved. From the measured absolute signals, the initial (in the first ten milliseconds) amount of impurities has been determined. Subsequently, the observed signals can be interpreted in terms of an impurity-recycling flux. It has been deduced from power balance considerations that this flux is confined to an external plasma shell, a small part only diffusing towards the centre to account for the independently inferred Zeff. The power radiated by the observed lines corresponds to an important fraction of the injected Ohmic power (∼ 30-40%). Two lines ascribed to Mo XXXI and Mo XXXII (and therefore originating in the central hot plasma core) have been detected for electron temperatures greater than 1.5 keV.