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More X-ray missions that will be operating in near future, like particular SIMBOL-X, e-Rosita, Con-X/HXT,
SVOM/XIAO and Polar-X, will be based on focusing optics manufactured by means of the Ni electroforming
replication technique. This production method has already been successfully exploited for SAX, XMM and Swift-XRT.
Optical surfaces for X-ray reflection have to be as smooth as possible also at high spatial frequencies. Hence it will be
crucial to take under control microroughness in order to reduce the scattering effects. A high rms microroughness would
cause the degradation of the angular resolution and loss of effective area. Stringent requirements have therefore to be
fixed for mirror shells surface roughness depending on the specific energy range investigated, and roughness evolution
has to be carefully monitored during the subsequent steps of the mirror-shells realization. This means to study the
roughness evolution in the chain mandrel, mirror shells, multilayer deposition and also the degradation of mandrel
roughness following iterated replicas. Such a study allows inferring which phases of production are the major
responsible of the roughness growth and could help to find solutions optimizing the involved processes. The exposed
study is carried out in the context of the technological consolidation related to SIMBOL-X, along with a systematic
metrological study of mandrels and mirror shells. To monitor the roughness increase following each replica, a multiinstrumental
approach was adopted: microprofiles were analysed by means of their Power Spectral Density (PSD) in the
spatial frequency range 1000-0.01 μm. This enables the direct comparison of roughness data taken with instruments
characterized by different operative ranges of frequencies, and in particular optical interferometers and Atomic Force
Microscopes. The performed analysis allowed us to set realistic specifications on the mandrel roughness to be achieved,
and to suggest a limit for the maximum number of a replica a mandrel can undergo before being refurbished.
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