Soft X-ray spectroscopy during Tore Supra ergodic divertor experiments

The soft X-ray impurity emission during ergodic divertor experiments, in Tore Supra tokamak, are studied. The experiments are performed with an extreme grazing incidence spectrograph. A powerful radial scan system, allowing the radial emissivity profiles of several soft X-ray lines to be recorded within a single discharge, is applied. The radial emissivity profiles of five light impurity lines are studied as a function of the magnetic perturbation introduced by the ergodic divertor. Perturbation effects on the radial position of the emissivity shells can be interpreted in terms of electron temperature gradient or transport modifications. The expected resonant effect is clearly detected. The system of radial scan associated to the Schwob-Fraenkel spectrograph is successfully operated. The available experimental data do not allow to choose between impurity transport and electron temperature gradient changes at the plasma edge as the cause of impurity ion emissivity profile modifications