Optical Metrology Laboratory

The main aim of the X-ray metrology lab is in general to achieve the complete characterization of the X-ray mirrors surface topocraphy. Improvement of focusing accuracy has been a major consideration in the use of grazing incidence optics in X-ray applications, e.g., synchrotron or FEL beamline instrumentation.
This task of paramount importance is achieved via accurate metrology. Profilometers measuring the global shape while roughness measurements ”sample” the optical surface. The treatment of complete topography of the optical surface is traditional divided in two principal branch: the study of profile at the long spatial wavelengths (in a range comparable with the mirror length) and the study of the microroughness at shorter spatial wavelength, by means of the Power Spectral Density (PSD). Owing to the finite scan size and resolution, each instrument has a finite window of spectral sensitivity. Therefore, we have to use different instruments, each one is sensitive only to a particular window of spatial frequencies. The Power Spectral Density provides a global description of the statistical properties of the roughness over a vast spectral extent.
In the following we describe the instrumentation used at X-ray metrology Lab for characterizations performed on mirror samples.