A flexible readout electronics for CZT arrays with real time digital signal processing

In the framework of an on-going R&D program on CZT detectors for astrophysical applications, we have started a study to address peculiar problems affecting this kind of detectors (e.g. response dependent on the interaction depth and multiple hit events) using a digital approach: the output of an analog front end chain based on a fast charge preamplifier, which preserves the shape of the signal as generated by the detector, sampled with a fast ADC, is processed to extract information to improve the performance, in particular the energy resolution. In this context, we have developed a flexible readout electronics to be used to characterize CZT array and test digital processing algorithms. The system includes analog front-end electronics, digital signal processing based on an FPGA board, and a Gb Ethernet interface for PC-based data acquisition. Current scheme allows the readout of a 4x4 pixels, which allows us to test the algorithms even for multi-pixels events and checking cross-talk effects. However, the system has been designed to be easily extended to an higher number of pixels by duplicating the Analog Front End board. Up to 4 AFEE boards can be managed by the system (thus supporting 64 channels, allowing a 16x16 array to be readout). Performance of the system with a commercial 4x4 pixels CZT (eV-products) will be reported in the paper.