In situ RBS study of the kinetics of galena thermal oxidation by means of 4He external micro-beam

In situ RBS measurements with an external He ion micro-beam have been performed on galena heated at temperatures varying from 400 deg. C to 600 deg. C, to study dynamically its oxidation kinetics. At each temperature, a millimetre-sized crystal is placed in a specially built oven directly facing the exit window of the beam. The thickness of the oxidised layer is measured every 2 min by means of the lead signal in the RBS spectrum, using a 3 MeV 4He2+ external focused beam (about 100 μm). We infer the diffusion mechanism from the growth of a phase, which is more or less stable when increasing temperature. This probing beam allows one to characterise layers of thickness extending from about 100-2000 nm