Performance of supersmooth x-ray mandrels for new hard x-ray missions

Abstract

Focusing mirrors manufactured via galvanic replication process from negative shape mandrels is the candidate solution for some of next future X-ray missions. Media Lario Technologies (MLT) is the industrial enabler developing, in collaboration with Brera Astronomical Observatory (INAF/OAB), the Optical Payload for future Hard X-ray mission. Concerning mandrel technology, MLT is engaged in a development programme aiming at improving the mandrels performance and their production rate. The angular resolution and the reflectivity of the mirrors replicated from the mandrels are strongly dependent on the mandrel performances and their stability. High throughput X-ray missions, require the massive production of mandrels in a short time, with angular resolution better than 7 arcsec Half Energy Width (HEW) and a surface micro-roughness in the order of 0.3 nm RMS. In order to achieve these results, several technological aspects are under investigation using a proprietary multistep surface finishing process. In particular, the metrology and the estimated optical performances of the mandrel are computed by means of dedicated post-processing and herein reported. Microroughness, medium scale errors, azimuthal slope error, axial slope errors, and mechanical dimensions are the quantities that have been measured by using atomic force microscope, high resolution optical profiler, contactless rotondimeter and high accuracy axial profilometer.