DEAP-3600 Dark Matter Experiment Data Acquisition and trigger system

The DEAP-3600 experiment will search for dark matter particle interactions on liquid Argon at SNOLAB, located 2 km underground in Sudbury Ontario. The DEAP-3600 detector is currently under construction and will be instrumented with 255 Hamamatsu PMT, each channel being decoupled from the PMT high voltage by a set of custom analogue signal conditioning boards. The signal conditioning boards split the PMT signals into three outputs: high gain; low gain; and into a twelve channel analogue sum (ASUM). Three different digitisers sampling at 250 MS/s, 62.5 MS/s and 50 MS/s digitise the signal conditioning outputs, the 50 MS/s sampler being a custom 6U VME Stratix IV FPGA based module generating trigger decisions based on a pulse-shape discrimination (PSD) selection. The 250 MS/s and 62.5 MS/s digitisers are commercial CAEN V1720 and V1740 modules respectively. DAQ from the digitisers to disk is handled by the Midas system with additional software event filtering provided by DEAP-3600 specific algorithms. With a total mass of 3600 kg the expected Argon β decay background is 3.6 kHz, a key feature of the DEAP-3600 TDAQ system is the reduction in data volume from 4500 MB/s to 5 MB/s, while recording all events of interest.