Performance Investigation On A Two Dimensional Position Sensitive CsI(Tl) Scintillation Detector

Position sensitive detectors play an important role in many fields,such as experimental nuclear physics,particle physics,astrophysics,geological exploration,Nuclear Medicine and so on.In Radioactive Ion Beam(RIB)Physics,beam should be diagnosed to get high quality RIB.To measure the size,position and density distribution of the beam more accurately,detectors with good position resolution are needed.Therefore,it's necessary to investigate performances of these detectors and find out some reasonable approaches to improve them.The purpose of this work was to investigate the performance of a two dimensional position sensitive CsI(T1)scintillation detector readout with position sensitive photomultiplier tube(PSPMT).It consists of a CsI(T1)crystal whose sensitive area is 60mm⁶0mm and thickness is 10mm, and a PSPMT with an effective area of 60mm×55mm.The front and end surfaces of CsI(T1)crystal are polished,and all the surfaces except for the end coupled to the photocathode directly are wrapped with 6μm aluminum foil as reflective coating.The PSPMT has crossed wire anodes,18 and 16 wires for X and Y directions respectively.It's tested with RIB ¹⁷N(32MeV/u)in Lanzhou,and obtained a good position resolution of 0.81 mm(FWHM)in both X and Y directions.The two dimensional position sensitive CsI(T1)scintillation detector was simulated by using the Monte Carlo code GEANT4 in this paper.The results demonstrated that the detector's performance would be better with the increasing of aluminum foil's reflection factor.The position resolutions obtained were 0.716mm,0.758mm,0.764mm and 0.776mm while the reflection factor equaled to 0.8,0.618,0.5 and 0.4.In addition,we investigated the affection of organic light guide while the reflection factor of aluminum foil was 0.4.Simulated results were 0.818mm,0.845mm,1.046mm and 1.335mm while the length of the light guide equaled to 2.0mm,4.0mm,8.0mm and 12.0mm. Obviously,simulated results were in good agreement with the experimental ones.Finally,the main factors,which can affect performance of the detector,and some planned detector improvements were presented.