Helium doped plasmas on FTU

In order to extend observations on the spontaneous electron density peaking in Neon doped plasmas already reported in FTU [1], some sessions have been performed by injecting Helium gas on the L-mode plasmas during the last two experimental campaigns. This favorable scenario, which can fall within so called “highly radiative” or “plasma detachment” themes, is investigated in this paper. It has been recorded that, not only the total amount of puffed Helium, but also the rate of injection can intervene in triggering a particle inflow. VUV spectroscopy measurements can help to evaluate the fraction of electrons that can be attributed to the ones stripped by Helium ionization in the electron density rise, at this purpose a model to estimate concentrations of impurities is proposed. The description of the Helium effect on plasma behavior, especially with respect to the density peaking and edge conditioning, by varying plasma parameters and shape, is exposed.