Characterisation of Hybrid Photon Detectors for the LHCb experiment

The Ring Imaging Cherenkov detectors of the LHCb experiment will enable charged particle identification across a wide momentum range. Cherenkov light will be detected using Hybrid Photon Detectors (HPDs). In an HPD, photoelectrons are produced in a multialkali photocathode, accelerated and focused by an electrostatic field, and detected by a pixellated silicon diode. HPDs are currently in production, and are undergoing testing to characterise their performance. A selection of test results are discussed here.