A systematic study of LYSO:Ce, LuAG:Ce and GAGG:Ce scintillating fibers properties

Properties of different scintillating fibers were examined and compared, as a part of the design optimization of the SiFi-CC detector, currently under development for proton therapy monitoring. Three scintillating materials were considered as candidates to constitute the active part of the detector: LYSO:Ce, LuAG:Ce and GAGG:Ce. All investigated samples had an elongated, fiber-like shape and were read out on both ends using silicon photomultipliers (SiPMs). Samples of LYSO:Ce material provided by four different manufacturers were included in the survey. Additionally, different types of optical coupling media, wrapping and coating materials were investigated. The following properties of the scintillating fibers were determined. attenuation length, position-, energy-, timing resolution and light collection. Two models were used to describe the propagation of scintillating light in the fiber and quantify the light attenuation: exponential light attenuation model (ELA) and exponential light attenuation model with light reflection (ELAR). Energy and position reconstruction were also performed using the two above methods. It was shown, that the ELAR model performs better in terms of description of the light attenuation process. However, energy and position reconstruction results are comparable for the two proposed methods. Based on the results of measurements with scintillating fibers in different configurations we concluded that LYSO:Ce fibers wrapped in Al foil (bright side facing towards the fiber) provided the best trade-off between the energy- (8.56% at 511 keV) and position (32 mm) resolutions and thus will be the optimal choice for the SiFi-CC detector. Additionally, the study of different optical coupling media showed, that the silicone pads coupling ensures good stability of the system performance and parameters.