A compact data acquisition system for TOHR multidetectors: time encoding for both time and energy measurements

TOHR is a high-resolution nuclear tomography system dedicated to imaging small live animals. We describe a fast PC-based data acquisition system used to acquire, assess, and store TOHR data. The system can handle high event rates (200 K quadruple-coincidence events/s) from the 15 TOHR photodetectors. High-level system control is provided by a Labview program running on a PC, while a fast, flexible data acquisition protocol is micromanaged by a digital signal processor (DSP) board housed in a PC. Essential hardware components, including detector-mounted charge-to-time converters, a data-routing multiplexer (FPGA based), and fast time-to-digital converters (225-ps resolution), are described in detail. This data acquisition system could be used in physics experiments.