High Z material operation in FTU

High Z materials, as possible plasma facing components for a fusion reactor, are being re-evaluated due to their advantages connected to the low sputtering yield and small erosion. A data base of experimental results related to their use on present Tokamak is missing. FTU has carried out a series of experiments with different medium and high Z limiter materials, Ni, Mo, and W, to improve the knowledge of the plasma behavior in these conditions. The results on plasma operation, core parameters, impurity content, and corresponding radiation losses are presented, and compared with those obtained with a low Z dominant impurity (siliconization). A simple model coupling the SOL and the plasma core is able to reproduce the experimental results, indicating that sputtering and self-sputtering are the main physical mechanisms of impurity production. © 1995 American Institute of Physics.