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ADC based DAQ System for the PANDA Straw Tube Tracker

This instrument consists of several sub-systems to provide precise trajectory reconstruction, energy and momentum measurements and particle identification. The central tracking system is the PANDA Straw Tube Tracker, which consists of 4224 drift tubes or straw tubes.
Straw tubes are gas filled tubes with a wire under high voltage along their axis. When a charge particle transverses the straw tube, ionization takes place and electrons drift toward the wire where an avalanche multiplication takes place. This allows the readout of the electric signal.

The aim of the DAQ system is to sample the pulses generated by the straw tubes to calculate the drift radius and charge. Drift radii of all straw tubes involved allow the reconstruction of the track of the particle. Through calculation of charge, particle identification can be done.
By sampling the whole signal, one can make use of pulse shapes and coincidences to extract the drift times. Since the processing has to be done under high rates (up to 1 MHit/s) a real-time processing is needed. Furthermore the space is limited due to other sub-systems, so the system has also to be compact.

Our DAQ system is based on the openVPX crate standard and makes use of its concept of Rear Transition Modules. Straw Tube signals are feed in to the Rear Transition Modules, where analog amplification and shaping takes place. At the front modules sampling and processing is done.

The sampling and processing unit is designed to reach a very high system integration level and allows data sorting and clustering in real-time. Using a modular communication interface, results can be send to the backend system.