Spectroscopy and timing with Multi-Pixel Photon Counters (MPPC) and LYSO scintillators

We have studied the performance of Hamamatsu multi-pixel photon counter (MPPC) devices for scintillation light readout. Two types of MPPC devices, both with a sensitive area of 1 mm times 1 mm and 400 and 1600 pixels, respectively, have been tested with LYSO scintillators matched to the active area of the MPPC. The measurements covered an energy spectrometry under illumination with Cs-137 and Na-22 radiation and timing resolution for 511-keV annihilation quanta. We measured an energy resolution of 19% FWHM and 24% FWHM for the 511-keV photopeak in the 400-pixel and 1600-pixel MPPC, respectively. In both MPPCs we obtained timing resolution of 0.9 ns plusmn 0.1 ns FWHM measured with the reference detector of BaF₂ crystal coupled to a photomultiplier tube. In separate measurements the MPPC single photoelectron distributions have been recorded and static reverse current-voltage characteristics were measured. The results are very promising for the application of MPPC in scintillator-based high resolution positron emission tomography.