Development of the fast and efficient gamma detector using cherenkov light

In this presentation we describe the development of a gamma detector using Cherenkov-only light. Such a device is foreseen for the detection of 511 keV photons from the positron annihilation and provides simultaneously the extremely high resolution in time and large efficiency. The main application of such a detector is the positron detection using the time-of-flight (TOF) technique, which plays an important role in the positron emission tomography (PET). It has an application in the material science for the positron annihilation lifetime spectroscopy technique and could be important for the particle identification in high energy physics. The gamma detector consists of a PbF 2 crystal coupled to a micro-channelplate photo-multiplier (MCP-PMT). The ability to detect 511 keV photons by such crystal has been demonstrated, but detection efficiency is found to be rather small, less then 10% [1], due to the limited number of photons produced by the Cherenkov effect. The low efficiency is a major limiting factor for making very fast TOF PET devices. We propose an innovative solution to overtake this limitation and reach simultaneously resolution in time better than 100 ps (FWHM) and the detection efficiency of about 50%. We describe the results of the first test of a complete detector chain with radioactive positrons source 22 Na.