A development of waveform sampling readout board for PET using DRS4

High speed (≥ 1 GHz) digital waveform sampling is one approach to achieve precise timing and also simplify the data acquisition of positron emission tomography (PET). Such waveform sampling technology becomes more reliable due to recent developments in modern chip technologies. We developed a prototype waveform sampling board using the Domino Ring Sampler (DRS4) chip for a PET data acquisition. The board provides eight channels which have 1 V input dynamic range and the maximum sampling speed of 5 giga-samples per second (GS/s). After amplitude and time calibrations on all the capacitor cells, noise level of each channel is measured to be ~1.5 mV (RMS), and ~8 ps (FWHM) of electronic time resolution is measured for single channel. As a demonstration, the board was used to readout the waveforms from two Hamamatsu R9800 PMT/LSO detector modules in coincidence setup. From the preliminary analysis, 12.6% FWHM of energy resolution and ~277 ps FWHM of coincidence time resolution were obtained using 511 keV photo-peak data.