A STUDY OF IMPURITY TRANSPORT IN THE PLASMA BOUNDARY OF TEXTOR USING GAS PUFFING

The transport of carbon and oxygen impurities has been studied in TEXTOR by introducing the gases CH4 and CO through a small hole in a test limiter. The toroidal distributions of different charge states of the impurities have been measured using a CCD camera with optical filters. Local impurity ion temperatures have been calculated from the Doppler broadening of line emission measured with a high resolution spectrometer. The spatial distributions and the ion temperatures have been modelled using the LIM Monte Carlo impurity code, with experimentally measured plasma profiles. Good agreement is obtained for both sets of measurements. The comparison shows the breakup energies of the atomic fragments to be << 1 eV. The fuelling efficiency of different gas species is discussed.