A novel high resolution XRF spectrometer for elemental mapping based on a monolithic array of Silicon Drift Detectors and on a polycapillary X-ray lens

This paper describes a novel x-ray fluorescence spectrometer designed for elemental mapping applications. The spectrometer is based on a ring-shaped monolithic array of silicon drift detectors (SDDs) with a hole in the center. The coaxial x-ray excitation beam, focused by a polycapillary x-ray lens, reaches the sample after passing through the central hole. This geometry optimizes the useful solid angle for collecting the fluorescence from the sample, while the optics maximizes the photon density in the excitation spot. These features, together with the very high detection rate of SDDs, allow a high scanning rate in elemental mapping to be achieved. Moreover, the spectroscopic resolution of SDDs (cooled by thermoelectric Peltier elements) is comparable to that of the classical Si(Li) liquid nitrogen-cooled detectors. Several examples of applications of the novel spectrometer in various fields, from archeometry to biology, are presented. This paper introduces also a new multi-element detector based on SDDs whose structure has been specifically optimized for very high resolution and very fast elemental mapping.