Optimization of positron-lifetime measurement geometry based on geant4 simulation

Abstract

Proper choice of measuring geometry and experimental setup of nuclear instrumentation modules and photomultipliers is a key element which a ects substantial positron lifetime measurement properties: count rate and time resolution. An adequate compromise must be found, when it comes to geometry of measurement. The optimal geometry using three detector layout is inspected in this paper. During our work, we concentrated on the simulation of XP2020Q photomultipliers and the BaF2 scintillator material. The Geant4 simulation allows to estimate an influence of the measuring geometry on detection e ciency and to choose the most appropriate crystals dimensions and positions. As mentioned in paper of Bečvaŕ et al., slight changes in geometry result in distortion or improvement of measured results. Experimental results already showed, changes of start crystals dimensions can result in significant increase in count rate of three-detector measurement.