XRF spectrometers based on monolithic arrays of silicon drift detectors: elemental mapping analyses and advanced detector structures

This paper describes a new X-ray fluorescence spectrometer based on a ring-shaped monolithic array of silicon drift detectors (SDD), presents several examples of the application of this instrument in elemental mapping analyses and introduces a new multi-element detector based on SDDs whose structure has been specifically optimized for very high energy-resolution and very fast sample scanning in elemental mapping. The existing spectrometer is based on a ring-shaped monolithic array of SDDs with a hole cut in its center. The coaxial X-ray excitation beam, focused by a polycapillary X-ray lens, reaches the sample going through the central hole. This geometry maximizes the solid angle for the collection of the fluorescence from the sample and minimizes the absorption of the fluorescence from the air. The X-ray optics maximizes the photon density in a small diameter excitation spot. These features, together with the very high detection rate of the SDDs allow to reach high scanning rate in elemental mapping. A few examples of the new spectrometer in archaeometry and biology are presented. The paper introduces also a new multi-element detector based on four SDDs monolithically integrated in a silicon chip and surrounding a hole cut in its center. The structure of the four SDDs has been specifically designed to obtain very high energy-resolution and peak-to-background ratio. The structure of the chip has been optimized for elemental mapping applications. The first experimental results obtained with this detector are here presented.