Performance Evaluation of an Advanced XRF Elemental Mapping System Featuring a Novel Ring-Shaped Monolithic Array of Silicon Drift Detectors

This paper introduces an ultra-fast X-ray fluorescence (XRF) spectrometer based on a novel ring-shaped semiconductor drift detector (SDD) and on a novel readout and processing electronics and discusses its performance. The new detector is based on 4 independent "droplet" type SDDs monolithically integrated on the same chip. The detector shape optimizes the collection angle of the fluorescence radiation. The X-ray excitation beam is focused on the sample by means of a polycapillary lens through the hole cut in the center of the detector. The "droplet" type SDD is characterized by a better energy resolution and a better peak-to-valley ratio with respect to the ones of "conventional" SDDs. The energy resolution is of the order of 140 eV FWHM on the Mn Kalpha line with 1 mus shaping time at -15degC and the peak-to-valley ratio is of the order of 6000. In order to fully exploit the detection rate performance of this detector we have developed a novel read-out electronic unit with selectable shaping time and on-board histogramming capability.