Time-of-flight measurements with Cherenkov photons produced by 511 keV photons in lead crystals

The resolution of time-of-flight measurements is usually limited by the decay time constant of the scintillating material used. If Cherenkov photons, which are produced promptly, could be used to measure the time-of-flight, the limiting factor would become the photo detector. The excellent time resolution of the microchannel plate photomultiplier (MCP PMT) lead us to consider the possibility of performing such time-of-flight measurements for pairs of annihilation 511 keV photons, which are used in positron emission tomography (PET) for source distribution reconstruction. In this work we present simulation and experimental results, obtained with a simple back-to-back detector, using PbF2 or PWO crystal as Cherenkov radiator and Hamamatsu MCP PMT as a photo detector.