Evaluation of ICRF heated discharges with boron coated molybdenum tiles

One of the primary utilization challenges is to minimize impurity production associated with ICRF operation. In present experiments, boronization is frequently applied to control impurities and its lifetime has been observed to be proportional to number of RF Joules injected. We have also observed that RF sheaths localized to field lines connected to the active antenna were responsible for the boron erosion and subsequent impurity generation. In an effort to identify important erosion and impurity source locations, we have vacuum plasma sprayed $\sim $100 $\mu $m of boron on molybdenum tiles from the outer divertor shelf, main plasma limiters, and the RF antennas. We have also modified the shape of the main plasma limiter and increased our spectroscopic monitoring diagnostics of the main plasma limiter. We have installed a set of probes to monitor the plasma potential and RF fields on field lines connected an antenna. Results from experiments investigating plasma performance and ICRF generated impurities will be presented.