Impurity profiles and radial transport in the EXTRAP-T2 reversed field pinch

Radially resolved spectroscopy has been used to measure the radial distribution of impurity ions (O III-O V and C III-Cvt) in the EXTRAP-T2 reversed field pinch (RFP). The radial profile of the emission is reconstructed from line emission measured along five lines of sight. The ion density profile is the fitted quantity in the reconstruction of the brightness profile and is thus obtained directly in this process. These measurements are then used to adjust the parameters in transport calculations in order to obtain consistency with the observed ion density profiles. Comparison between model and measurements show that a radial dependence in the diffusion is needed to explain the measured ion densities.