Fast and efficient detection of 511 keV photons using Cherenkov light in PbF₂ crystal, coupled to a MCP-PMT and SAMPIC digitization module

We study the possibility to use the Cherenkov light for the efficient detection of 511 keV photons with the goal to use it in TOF-PET . We designed and tested two detection modules consisting of PbF₂ crystals attached to Planacon MCP-PMT XP85012. Amplified PMT signals are digitized by the SAMPIC module with high readout rate, up to 10⁵ events/s, and a negligible contribution to the time resolution, below 20 ps (FWHM) . We developed a fast 2D scanning system to calibrate the PMT time response and studied in details the timing characteristics of the Planacon PMT. Using a radioactive ²²Na source we measured a detection efficiency of 24% for 511 keV photons in a 10 mm thick crystal and a coincidence resolving time of 280 ps. We analyzed the main factors limiting the time resolution of the large-surface detection module and proposed solutions to improve it, which will be tested in our future project.