Boron deposition on the graphite tiles of the RFX device studied by secondary ion mass spectrometry

We report on a systematic surface analysis of the graphite tiles coming from different locations on the first wall of the reversed-field pinch device RFX by secondary ion mass spectrometry. Both boron and the main contaminant species were investigated. The largest values of the total boron intensity are found for tiles positioned in front of the injection valve, the lowest for those at the gap. The in-depth profiles of the normalized boron signals are interpreted as signatures of a plasma–wall interaction, namely of the plasma coming in contact with the wall in restricted regions, mainly determined by the magnetic field configuration, during its lifetime.