Photon Detectors for the Ring Imaging Cherenkov Counters of the LHCb Experiment

This thesis reports on the author’s contribution to the development of the Ring Imaging Cherenkov(RICH) detectors in the LHCb experiment due to take data at the CERN Large Hadron Collider in 2007. The first chapter summarises the physics to be explored by the LHCb experiment; measurements of CP violating asymmetries and a study of rare B decay modes. A brief overview of other experiments studying B-physics is presented. The experiment itself is then described, focussing on the RICH system used for particle identification, with particular emphasis on the photondetectors. The thesis then reports on the work done by the author on the design of the RICH1 Magnetic Shield, that allows the photon detectors to operate in the fringe field of the LHCb dipole magnet, while fulfilling the conflicting requirement to provide additional magnetic bending power to aid the LHCb charged particle trigger. The design of all of the many sections of the shield are described in depth and the results of finite element simulations performed by the author are reported. The results of measurements the author took of the field produced by the completed magnetic shield are then evaluated and compared with the simulation. Next follows a study undertaken by the author on the electronic readout of the RICH Hybrid Photon Detectors (HPD). Two related mesurments were made, a novel series of timing tests on the HPD’s analogue readout in an assembled tube and a series of experiments using a pulsed laser to simulate the charge deposition of a photoelectron. The final part of the thesis describes the analysis of data taken in a charged particle beam studying the Cherenkov photon yield seen with a teest RICH system and the prototype HPD electronics chain. This work links the laboratory timing studies with measurements performed in the testbeam, and compares the efficiency of the HPDs with predictions.