X-Ray Silicon Drift Detector – CMOS Front-End System with High Energy Resolution at Room Temperature

We present a spectroscopic system constituted by a Silicon Drift Detector (SDD) coupled to a CMOS charge sensitive preamplifier, named SIRIO, specifically designed to reach ultimate low noise levels. The SDD, with an active area of 13 mm2, has been manufactured by optimizing the production processes in order to reduce the anode current, successfully reaching current densities between 17 pA/cm2 and 25 pA/cm2 at +20C for drift fields ranging from 100 V/cm to 500 V/cm. The preamplifier shows minimum intrinsic noise levels of 1.27 and 1.0 electrons r.m.s. at +20C and -30C, respectively. At room temperature (+20C) the 55-Fe 5.9 keV and the pulser lines have 136 eV and 64 eV FWHM, respectively, corresponding to an equivalent noise charge of 7.4 electrons r.m.s.; the noise threshold is at 165 eV. The energy resolution, as measured on the pulser line, ranges from 82 eV FWHM (9.4 electrons r.m.s.) at +30C down to 29 eV FWHM (3.3 electrons r.m.s.) at -30C.