The data acquisition system of ClearPET/spl trade/ Neuro - a small animal PET scanner

The Crystal Clear Collaboration has developed a modular system for a small animal PET scanner (ClearPETtrade). The modularity allows the assembly of scanners of different sizes and characteristics in order to satisfy the specific needs of the individual member institutions. The system performs depth of interaction detection by using a phoswich arrangement combining LSO and LuYAP scintillators which are coupled to multichannel photomultipliers (PMTs). For each PMT a free running 40 MHz ADC digitizes the signal and the complete scintillation pulse is sampled by an FPGA and sent with 20 MB/s to a PC for preprocessing. The pulse provides information about the gamma energy and the scintillator material which identifies the interaction layer. Furthermore, the exact pulse starting time is obtained from the sampled data. This is important as no hardware coincidence detection is implemented. All single events are recorded and coincidences are identified by software. The system in Julich (ClearPETtrade Neuro) is equipped with 10240 crystals on 80 PMTs. The paper presents an overview of the data acquisition system