A modular DAQ system for ultra-fast sampling for application in High Energy and Astroparticle physics

We present a new compact Acquisition System suitable for use with detectors for High Energy and Astroparticle. An interface board, called CAPR1 (CAlibration PRotocol ONE), receives the analog signals and provides the proper impedance matching with the possibility to select the desired polarity and change the input common mode. The signals are transmitted differentially to a second board, called DRS2 mezzanine where sampling and digitizing are performed. The DRS2 mezzanine is based on a low power analog sampler (Domino Ring Sampler) with frequency ranging from 1 to 4.5 GHz, while the data are digitized by two 12-bit resolution ADCs at 40 MHz for a total of 20 channels. Up to four DRS2 mezzanines are placed on a 9U VME motherboard called PULSAR (PULSer And Recorder), that performs data handling and reformatting. Since the current version of Domino Ring Sampler (DRS2) chip shows a non-linear behaviour, a data calibration procedure is necessary. This task is executed on the interface board by setting DC levels on a calibration path in place of the input signals. The calibration points for every DC value are extrapolated from the sampled data and the calibration curve is obtained. The DC levels are set by the motherboard using an SPI protocol through the same cable that is used for the analog transmission. Every PULSAR hosts up to 80 analog channels plus auxiliary digital signals for trigger and monitor purposes. The data are transferred to PCI memory via Gbit optical links using the CERN S-Link. The Data Acquisition system design and performances are described in detail.