Helium Doped Plasmas on FTU

On FTU some sessions have been performed by injecting Helium gas on the L-mode plasmas, in order to extend previous observations about Neon doping already reported. Not only the total amount of Helium, but also rate of injection intervenes in triggering a particle inflow; It's possible to reach the value of 5 in the electron density peaking. VUV spectroscopy measurements help to evaluate the Helium ionization, a model to estimate concentrations of impurities is proposed for the first time. The Helium effect on plasma behavior and edge conditioning is exposed.