Digital filtering and analysis for a semiconductor X-ray detector data acquisition

• Published in: Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment Vol. 571; no. 1; pp. 378 - 380
• Main Authors: Gerardi, Gaetano, Abbene, Leonardo, La Manna, Angelo, Fauci, Francesco, Raso, Giuseppe
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 01-02-2007
• Subjects: Digital shaping; Pile-up; Semiconductor detectors; X-ray spectroscopy; Semiconductor detectors; 07.85.Fv; 29.30.Kv; Pile-up; Digital shaping; X-ray spectroscopy; 07.50.Qx
• ISSN: 0168-9002; 1872-9576
• DOI: 10.1016/j.nima.2006.10.113

Pile-up distortion is a major drawback in X-ray spectroscopy at high count rate. Pulse width narrowing with shaping techniques can lead to the reduction of the pile-up distortion, but a low shaping time reduces the noise filtration and leads to a poor energy resolution. Thus, only a best compromise solution between the pile-up and the noise requirements is achievable. The hardware manipulation needed to adjust the parameters of the traditional electronic shaping amplifiers makes it uneasy to tests various settings in different conditions. Digital techniques can help to overcome such difficulties. A digital signal processing and analysis system for X-ray spectroscopy is described in this paper. The system processes the output signal of a Charge Sensitive Preamplifier (CSPA) connected to an X-ray semiconductor detector. The output CSPA signal is registered with a high speed ADC (sampling rate up to 100
MS/s, 14
bit resolution) and a fully digital shaping is performed off-line by a dedicated software instead of analog electronics. The software carries out the rest of data analysis (peak detection, pile-up recognition, rejection or correction) and finally calculates the photon count, constructs the spectrum and extracts other useful information. We processed the output signals of an Amptek
® XR-100
T CdTe detector used with mammographic X-ray beams. We developed the system with the LabVIEW
® platform. The software is characterized by a user friendly GUI which make it easier to change settings than traditional electronics.