Time of Flight Measurement of 511 keV annihilation photons with Multigap RPCs

The timing properties of MRPC detectors to 511 keV annihilation photons has been investigated in view of a possible biomedical application, such as Time of Flight Positron Emission Tomograph (ToF-PET). Using a 22Na source we measured the Time-of-Flight (ToF) information, from which we extracted the MRPCs time resolution. The time resolution (FWHM) has been founded to be 313 ps for a single MRPC (with four 250 μm gas gap) by considering only a couple of detectors. A time resolution (FWHM) of 376 ps has been measured for the overall setup (two independent pairs of MRPCs). Hence, the good time resolution we obtained for our detectors makes them very attractive for a future employment in a PET prototype, even if a preliminary improvement of the efficiency is needed.