Impurity behaviour,radiation losses and wall effects in the T.F.R. machine

Spectroscopic, bolometric, soft X-rays and electrical measurements have been performed on T.F.R. up to 400 kA-60 kG. Light impurities appear very early. They are recycling in a stationary state during the current plateau. The heavy impurities density grows during the current rise, then levels off or increases slightly during the current plateau. The production of fast electrons is evaluated. Densities and fluxes of impurities are given. Photodesorption, photoelectron induced desorption, ion desorption, thermal desorption, evaporation and sputtering are discussed as possible candidates for the pollution.