The carbon impurity particle transport in ohmic discharges on the HT-7 tokamak

The line-integrated optical measurement of impurity radiation profiles for the study of light impurity transport is performed in the HT-7 tokamak. The carbon impurity line emissivity is obtained by Abel inversion. The radial transport behaviours of carbon impurities at different central line averaged electron densities \overlinen_\rm e are investigated in ohmic discharges. The diffusion coefficient D_k(r), the convection velocity W_k(r) and the total flux of the impurity ions \varGamma _k decrease with the increase of \overlinen_\rm e, which shows a reduction in the impurity particle transport at higher electron densities.