A sampling ADC data acquisition system for the electromagnetic calorimeters of COMPASS

For the readout of the two electromagnetic calorimeters of the two stage COMPASS spectrometer at CERN, a sampling ADC (SADC) based data acquisition system was developed. The shaped photomultiplier signals are continuously digitized with 80 MHz and processed within field programmable gate arrays (FPGAs). The FPGAs implement zero suppression, latency buffering and provide an option to derive online calorimeter trigger decisions. In total, 4704 calorimeter channels are currently read by two different SADC module types with 10 bit and 12 bit resolution, respectively. With modified FPGA firmware, the same modules are also used in other applications, e.g. for medical imaging (PET) and ultracold neutron experiments.