System Test of a Three-Column LHCb RICH-2 Prototype Detector

A three-column prototype of the downstream LHCb Ring Imaging Cherenkov detector (RICH-2) has been constructed. The prototype module contains six 8 cm diameter Hybrid Photon Detectors (HPDs), mounted in a close-packed arrangement, and read out at the full LHC speed of 40 MHz. Pairs of HPDs are read out with LHCb prototype on-detector RICH electronics utilizing radiation tolerant FPGA technology, optical links and 40 MHz trigger-timing and control (TTC). The columns have a modularized mechanical arrangement with compact high and low voltage distribution systems. A full system test of the readout has been verified. The three-column structure has been mounted in a Cherenkov vessel and Cherenkov rings have been observed from $N_2$ and $C_{4}F_{10}$ gas radiators in a CERN pion test beam.