Alumina-plasma interaction in the Petula Tokamak

In connection with the construction of an alumina vacuum vessel on the PETULA Tokamak, measurements of the outgassing properties of alumina and studies of alumina-plasma interaction have been undertaken. Outgassing rates of 10-11 to 10-12 torr 1/s cm2 are achieved for baking temperature ranging between 150 deg and 200 deg C. Two categories of results have been obtained from the studies of alumina-plasma interaction depending on the plasma interacting with the alumina. For dense and cold plasmas nsub(e) approximately equal to 1013, Tsub(e) equals a few eV, impurity concentrations lower than 1% are measured - ELISA experiment. For dense and hot plasmas, comparison between discharges produced with tungsten and alumina limiters shows an improvement of plasma characteristics in the case of alumina: ohmic power and oxygen contamination are significantly reduced