Performances of Rh and Mo mirrors under JET exposure

The aim of this work was to provide a comprehensive surface characterization of rhodium and molybdenum mirrors exposed on the main chamber wall of JET during campaigns with carbon plasma-facing components. As determined using X-ray photoelectron spectroscopy, Secondary Ion Mass Spectrometry, Scanning Electron Microscopy and optical measurements the co-deposits formed on the mirrors were composed of C, Be, Ni, Mo and Fe. Most of the metallic elements on the surface were in the oxidized states. After removing a part of the film by sputtering with Ar+ ions, Mo carbide state was studied by XPS. The reflectivity measurements showed the dependence of the thickness of the deposited film on the optical properties of the mirror: a thinner film on the Mo mirrors results in an identical reduction in reflectivity as that seen on the exposed Rh mirror.