A flexible high-rate USB2 data acquisition system for PET and SPECT imaging

A new flexible data acquisition system has been developed to instrument gamma-ray imaging detectors designed by the Jefferson Lab Detector and Imaging Group. Hardware consists of 16-channel data acquisition modules installed on USB2 carrier boards. Carriers have been designed to accept one, two, and four modules. Application trigger rate and channel density determines the number of acquisition boards and readout computers used. Each channel has an independent trigger, gated integrator and a 2.5 MHz 12-bit ADC. Each module has an FPGA for analog control and signal processing. Processing includes a 5 ns 40-bit trigger time stamp and programmable triggering, gating, ADC timing, offset and gain correction, charge and pulse-width discrimination, sparsification, event counting, and event assembly. The carrier manages global triggering and transfers module data to a USB buffer. High-granularity time-stamped triggering is suitable for modular detectors. Time stamped events permit dynamic studies, complex offline event assembly, and high-rate distributed data acquisition. A sustained USB data rate of 20 Mbytes/s, a sustained trigger rate of 300 kHz for 32 channels, and a peak trigger rate of 2.5 MHz to FIFO memory were achieved. Different trigger, gating, processing, and event assembly techniques were explored. Target applications include >100 kHz coincidence rate PET detectors, dynamic SPECT detectors, miniature and portable gamma detectors for small-animal and clinical use