Behaviour of oxygen impurities in the Frascati Tokamak

The transport of oxygen in a high-density, long-duration discharge of the Frascati Tokamak (FT) was studied both experimentally and numerically. Low ionization states peak quite internally where T e =150 eV and n e =0.8 10 14 cm -3 . A code (OSSFTC) was prepared including atomic processes and transport phenomena. Neoclassical collisional transport and charge exchange processes are inadequate to justify this phenomenon and there is evidence of strong anomalous diffusion. The values and the radial dependence of the diffusion coefficient are presented for different phases of the discharge.