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Description
Summary
Many experiments in astroparticle physics require the acquisition of high-speed signals coming from a large number of photo-multipliers tubes (PMT).
Usually, the signal of interest of a single PMT is limited to relatively short pulses (10 to 20 ns) generated by specific events.
The detector requires continuous acquisition, but only the data (sampled data and time of the pulse) associated with these pulses is of scientific interest.
This contribution presents the implementation and performances of a novel system for data reduction and software group trigger to satisfy these needs.
The system is based on NI PXIe-5162 waveform digitizers (4 channels, 1.25 GSample/s/ch)
and has been tested on the outer detectors of the DarkSide-50 experiment, composed by a liquid scintillator equipped with 110 PMTs and a water Cherenkov detector equipped with 80 PMTs.
Each channel of the waveform digitizer is able to identify pulses and perform zero suppression.
When a pulse is identified, a 64 bit time-stamp, that encodes the time of the pulse and his geographical id, is generated.
Time-stamps can be read independently from the sampled data of the pulses.
The trigger of the system is entirely generated by software, that continously reads the time-stamps and evaluate group trigger conditions.
The sampled data (waveforms) of the pulses are only requested by the DAQ when the software group trigger is issued.
The description of the system, implementation of the DAQ, results, and scalability to next generation experiments are discussed in this contribution.
