Simulation Of The Performance Of Scintillation Detector For The Muon Scattering Imaging

Nuclear material detection for nuclear safety is an important subject in the devel-opment of nuclear technology.For traditional methods of nuclear material detection like X-ray and gamma-ray imaging,there are many difficulties in practical applications due to their low penetration capabilities in materials of high atomic number.On the other hand,cosmic ray muon,as a natural radiation source,has strong penetrability since muon doesn't participate in the strong interaction.It can be used for the pas-sive detection and imaging of high atomic number materials in various environments.The technology of cosmic-ray imaging has great application potential in many fields,such as geological exploration,oil industry,nuclear waste monitoring,etc.This paper presents the R&D of a cosmic ray imaging detector,which provides a potential solution for customs inspection and safety monitoring on radioactive nuclear materials.The principle of cosmic ray muon scattering imaging was proposed by Los Alamos National Laboratory in 2003.The scattering angle of a muon is dependent on the atomic number of the materials it passes through(the higher atomic number leads to the larger scattering angle).Therefore,by measuring the muons' scattering angles,it is possible to calculate the atomic number and density distribution of the object,and reconstruct its image by a certain algorithm.This imaging technology mainly involves a muon track-ing detector,measuring the muon' s incident and exit path to calculate its scattering angle.To identify different materials with different muon scattering angles,the angu-lar resolution of the tracking detector is a key parameter in the muon image system.In recent years,research institutions and laboratories around the world have developed various experimental prototypes of moun imaging technology and began to apply them in customs inspection,nuclear reactor detection,etc.However,there are still many difficulties to use them in complex outdoor environments.For example,tracking detec-tors used in many muon image systems are gas detectors(MRPC,GEM,micro Megas),which requires strict operating conditions.Most of them can only run in the laboratory.To avoid this problem,based on scintillation detection technology and muon scattering imaging principle,we design a muon imaging prototype that can be applied in various environments by using plastic scintillators as the tracking detector,simulate and test its performance,and develop the related positioning algorithm.This research provides a valuable reference for the R&D of future moun imaging systems.This paper is mainly focused on the study of the moun tracking detector consisted of triangular scintillators and a new type of silicon pixel detection unit(SIPM),which is selected as the photosensitive device to effectively improve the detection efficiency.To meet the requirement of accurate muon scattering imaging,the detector' s perfor-mance(including position resolution,light yield,etc)are simulated and compared with experimental data.The simulation program is based on GEANT4.We also develop the positioning algorithm and the system error correction algorithm to estimate the influence of multiply uncertainties.The simulated position resolution can achieve 1 mm(RMS).Compared with the experimental result,the position resolution difference is 0.05 mm(RMS)(the simulation does not involve the noise contribution of readout electronics),which proves the feasibility of the simulation method.Based on the GEANT4 and the experimental data from the selected triangular tracking unit as the reference,the simulation program of the imaging system is de-veloped.And the correlation between its imaging performance(angular resolution and acceptability)and geometry parameters are analyzed.The performance and geometric parameters of the imaging system are determined by the angular resolution required by the imaging(angular resolution 10 mrad).PoCA algorithm is used for object imaging.The result shows that the material with a high atomic number above iron(including iron)can be identified effectively,which meets the requirement and provides an impor-tant reference for further R&D.