Performance of a hybrid photon detector prototype with electrostatic cross-focussing and integrated silicon pixel readout for Cherenkov ring detection

We report on the first test beam performance of a hybrid photon detector pr ototype, using binary readout electronics, intended for use in the ring ima ging Cherenkov detectors of the LHCb experiment at the CERN Large Hadron Co llider. The photon detector is based on a cross-focussed image intensifier tube geometry. The anode consists of a silicon pixel array bump-bonded to a binary readout chip with matching pixel electronics. The detector has been installed in a quarter-scale prototype vessel of the LHCb using imaging Ch erenkov system. Focussed ring images produced by 120 GeV/c negative pions t raversing an air radiator have been recorded. The observed light yield and Cherenkov angle resolution are discussed.