Edge temperature and density measurements with a thermal helium beam in the RFX reversed field pinch

The electron temperature and density at the edge plasma of the reversed fie ld pinch experiment RFX are measured from the intensity ratio of selected s pectral lines emitted by an atomic thermal helium beam injected into the pl asma discharge. This technique, already performed in several Tokamaks, has been, for the first time, applied to a reversed field pinch to extend the e dge density and temperature measurements to high-current discharges where i ntrusive probes cannot withstand the high-power fluxes. The temperature at the edge increases with the plasma current and decreases with the plasma av erage electron density. These edge Values have been used to analyse the beh aviour of the impurity influxes. The influence of the edge temperature and density on the efficiency of carbon penetration has been studied by means o f a Monte Carlo simulation of the plasma behaviour at the edge.