RF plasma edge interactions and their impact on ICRF antenna performance in Alcator C-Mod

In Alcator C-Mod, we have investigated the compatibility of high power ion cyclotron range of frequencies antenna with high performance plasmas and all high-Z plasma facing components, to provide operational information for future devices such as ITER. Boronization appears to be critical achieving low radiated power plasmas but it can be quickly eroded particularly in the presence of ICRF. Here we present circumstantial evidence that suggests RF-enhanced sheaths on flux tubes connected from the antennas to the top of the outer divertor are the most likely erosion mechanism. In addition, antenna operation without a Faraday screen was found to degrade antenna performance through increased impurity sources.