FELIX based readout of the Single-Phase ProtoDUNE detector

The liquid argon Time Projection Chamber technique has matured and is now in use by several short-baseline neutrino experiments. This technology will be used in the long-baseline DUNE experiment; however, this experiment represents a large increase in scale, for which the technology needs to be validated explicitly. To this end, both the single-phase and dual-phase implementations of the technology are being tested at CERN in two full-scale (10×10×10 m$^3$) ProtoDUNE setups. Besides the detector technology, these setups also allow for extensive tests of readout strategies. The Front-End LInk eXchange (FELIX) system was initially developed within the ATLAS collaboration and is based on custom FPGA-based PCIe I/O cards in combination with commodity servers. FELIX will be used in the single-phase ProtoDUNE setup to read the data coming from 2560 anode wires organized in a single Anode Plane Assembly structure. With a sampling rate of 2 MHz, the system must buffer and process an input rate of 74 Gb/s. Event building requests will arrive at a target rate of 25 Hz, and loss-less compression must reduce the data within the requested time windows before it is sent to the experiment’s event building farm. This paper discusses the design of the system as well as first operational experiences.