Nanostructured rhodium films for advanced mirrors produced by Pulsed Laser Deposition

In this paper advantages in the production by Pulsed Laser Deposition (PLD) of nanostructured, nanoengineered rhodium films to be used in tokamak First Mirrors (FMs) are shown. The peculiar PLD capability to tailor film structure at the nanoscale gives the possibility to deposit low roughness Rh films with a wide variety of structures and morphologies. By a proper movimentation of the substrate and using high fluence (10 - 19 J/cm^2) infrared laser pulses, it has been possible to deposit planar and homogeneous Rh films effectively suppressing surface defects on areas of the order of 10 cm^2 with a satisfactory specular reflectivity. Multilayer deposition has been exploited to produce coatings with high adhesion and good mechanical properties. Finally, an estimation of the requirements to produce by PLD rhodium films suitable for the requests of ITER is provided.