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

Pile-up distortion is a major drawback in X-ray spectroscopy at high count rate. Pulse width narrowing with shaping techniques canlead 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 neededto 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 isdescribed in this paper. The system processes the output signal of a Charge Sensitive Preamplifier (CSPA) connected to an X-raysemiconductor 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 ofdata analysis (peak detection, pile-up recognition, rejection or correction) and finally calculates the photon count, constructs thespectrum and extracts other useful information. We processed the output signals of an Ampteks XR-100 T CdTe detector used withmammographic X-ray beams. We developed the system with the LabVIEWs platform. The software is characterized by a user friendlyGUI which make it easier to change settings than traditional electronics.