Characterization of a Hamamatsu R7600 multi-anode photomultiplier tube with single photon signals

We present measurements aimed to characterize the Hamamatsu R7600 multi anode Photon Multiplier Tube (PMT), in view of its application for a new generation of Ring Imaging Cherenkov (RICH) detectors at LHCb. Single photon signals were used as tools for characterization. A commercial blue LED slightly forward biased was the main source of photon light. Spectra obtained with this source coincided with those obtained with the Cherenkov light from a PbF₂ crystal and a ²²Na gamma source. Dark current and cross-talk performances were measured. PMT response was studied for single photon signals as a function of the dynodes bias level ratio and magnetic field. Results obtained so far showed that the R7600 PMTs are adequate for the LHCb RICH detectors at high luminosity.