| Cosmic ray muon scattering tomography technology takes advantage of the high energy and strong penetration properties of cosmic ray muons,which enable nondestructive imaging of materials.In addition,cosmic ray muons do not require the generation of artificial radiation sources to be generated,which can reduce imaging costs.In addition,cosmic ray muon scattering tomography provides excellent performance in identifying high Z materials and can also identify nuclear materials.Therefore,it can be used in scenarios such as nuclear waste monitoring.Based on research on traditional muon scattering tomography,the imaging system by adding a total reflection Cherenkov detector(DIRC)and a plastic scintillation fiber detector.The detector of Internally Reflected Cherenkov is used to obtain muon momentum information,and the plastic scintillation fiber detector is used to measure muon tracks.In the simulation of muon events,we construct the muon generator using the sea level muon flux formula and discrete sampling method to generate muon randomly.Then,multiple scattering effects of the muon in the MTS are simulated using the Toy Monte Carlo method,and detector effects are sampled.After obtaining the muon simulation events,the Kalman Filter algorithm is adopted to track reconstruction,providing the angular resolution of the imaging system and the position resolution of the muon at the boundary of the imaging interval.Subsequently,the momentumdependent Po CA imaging algorithm based on the traditional Po CA(Point of Closure Approach)algorithm is explored.Because of the different momentum resolutions of the DIRC,the range of momentum that can be measured is different.Therefore,it is necessary to explore the imaging results of momentum information in different momentum resolutions.By comparing the absolute reconstruction of radiation length and the discrimination power of materials,it was found that using muon events of low-momentum for imaging resulted has lower error and better discrimination power.Based on the exploration of the reconstruction methods mentioned above,this article explores the impact of the momentum resolution brought by DRIC detector and the spatial resolution brought by the tracker and provides of discrimination power between explosive RDX(low Z)and nuclear material U(high Z)and materials with similar radiation lengths.By analyzing the imaging results of low-momentum muon events with different momentum resolutions,it was found that the wider measurable energy spectrum range has the higher accuracy of radiation length and better material discrimination power.In addition,using events of true momentum in the entire momentum range with different spatial resolutions to image,it was found that the material which has smaller the deflection angle of the multiple scattering is more sensitive to the impact of position resolution.Finally,this article explores imaging algorithms and proposes an imaging case.Firstly,the materials are quickly distinguishing using muon events with unknown momentum between low and high Z materials.Then,the materials are accurately identified,and low Z materials are imaging using muon information with measurable momentum.However,for high Z materials,some low energy muons cannot penetrate the materials due to energy loss.The imaging results of material identification modified by utilizing the average values of high-momentum muons.The corresponding material discrimination power is provided based on the existing detector performance parameters. |
