The front-end electronics of the LHCb ring-imaging-Cherenkov system

The LHCb experiment at the CERN Large Hadron Collider will use ring-imaging Cherenkov detectors for particle identification. By measuring rings of Cherenkov photons generated by elementary particles traversing a radiative medium, these particles can be identified across a wide range of momenta. The photons will be measured by a new type of detector, the pixel hybrid photon detector (HPD). In total, 484 HPDs will be used, providing ∼500,000 channels of data. Specific readout electronics have been developed for processing the data from the HPDs, and this paper describes the design and testing of these devices together with the final system to be used in the experiment. Emphasis is on the application-specific integrated circuits that are encapsulated within the HPDs, allowing high channel density and low noise. These are subject to the strict requirements of efficient photon detection and reliability within the harsh environment of the experiment. Special interconnect techniques developed for this application are described. Finally, the additional electronics infrastructure to readout the full system of 500,000 channels is outlined, including data transmission and power distribution.