Characterization of coincidence time resolutions of TlBr _x Cl_1−x crystals as Cherenkov radiators

Abstract

The coincidence time resolutions of thallium bromide chloride (TlBrxCl1-x) crystals used as Cherenkov radiators were characterized. A pair of TlBrxCl1-x crystals with the same composition was used to coincidentally detect positron annihilation gamma rays from a 22Na source. The size of the crystals was approximately 3 mm × 3 mm × 3 mm. A polished surface of the crystals was coupled to a silicon photomultiplier. The time resolution improved with an increase in the Cl concentration in the crystals. TlBr0.3Cl0.7 crystals exhibited the best coincidence time resolutions of 378 ± 17 ps and 635 ± 31 ps with and without event selection based on the photoelectron level, respectively.