Seminars Archive

High resolution and high rate X-Ray spectroscopy with Silicon Drift Detectors.

Abstract
The development of radiation detectors for high-resolution X-ray spectroscopy is a research field of continuously growing interest, for its application either in scientific research or in industrial applications like X-ray fluorescence, X-ray diffraction and microanalysis with SEM. In most of the applications, especially when a mapping analysis is required, the general trend is to increase the count-rate. This reduces the measurement time or increases the accuracy thanks to the higher statistics. As alternative to Si(Li) detectors, silicon PIN diode and Ge detectors, high-resolution and high-rate silicon drift detectors (SDDs) have become a valuable solution in an increasing numbers of spectroscopy apparati. The figure-of-merit in terms of energy resolution and counting-rates is strictly dependent on the front-end electronics. Very recently, a new monolithic CMOS charge preamplifier (named “CUBE”) has been proposed as alternative to the more commonly used JFET solution [1]. Moreover a Digital Pulse Processor (DPP) developed for high resolution and fast X-Ray Spectroscopy will be presented. The system is principally suitable for spectrometers based on last generation Silicon Drift Detector (SDD) used in application with high speed elemental mapping. In this work, we compare the performances of the SDD + CUBE circuit with respect to the typical performances of the SDD + JFET transistor. We will show that CUBE enables to get superior energy resolution at short shaping time. As an example, Fig 1 shows the energy resolution with the two considered front-end. With CUBE, a FWHM resolution of the order of 130-135 eV @ 6keV at the short peaking time of 500 ns is possible (up to 500kcps Input Count Rate with dead time <50%). As shown in Fig 2, the energy resolution remains quite constant up to 1000kcps (input), and an output count rate up to 500 kcps has been recorded with a peaking time of 100ns. [1] L. Bombelli, C. Fiorini, T. Frizzi, R. Alberti, A. Longoni, Nuclear Science Symposium Conference Record, 2011, N40-5