Data acquisition of the crystal zero degree detector at BES III

The BES III experiment at the BEPCII electron positron collider in Beijing is collecting data in the charm-τ mass region. Being strongly peaked towards small polar angles, photons from initial state radiation (ISR) are detected with limited efficiency. In order to increase the detection efficiency of these photons, we propose a small detector comprised of two arrays of scintillating crystals separated by a small gap to be placed in the very forward and backward regions. The scintillation light will be collected by silicon photomultipliers (SiPMs) and the signals will be digitized by feature extracting flash ADCs. This data stream is correlated with the BES III trigger in realtime on FPGA based hardware. In this contribution the hardware of the data acquisition and the algorithms performing the feature extraction and the event correlation are presented.