Polycapillary parallel collimators for X-ray imaging: Experimental characterization of the energy and angular response function

The full exploitation of polycapillary X-ray lenses in X-ray imaging systems - e.g. based on X-ray fluorescence, X-ray diffraction, X-ray scattering - is strictly related to the critical angle for total X-ray reflection. This means that the output beam is strongly dependent on both the spatial and spectral properties of the incoming beam. Therefore, X-ray polycapillary optics need to tailor their design to the specific experiment and require a careful performance qualification. We carried out an experimental study of a parallel polycapillary collimator at the synchrotron and with a conventional X-ray generator in order to obtain a complete qualification of its energy-angular response function. The impact of other relevant effects like response uniformity and X-ray penetration, were studied. The obtained response matrix allows precise modeling of photon transport in the energy range of interest and qualifying the achievable performance with polycapillary technology when applied to X-ray scatter imaging.