Research On Muonenergy Measurement And Application In Muon Tomography

Cosmic ray muon tomography is a developing technology aiming at high-Z material detection with the advantage of strong penetrability and free of artificial radiation sources,able to break through the weakness of existing passive radioactive material detection technologies.But limited to the low flux of natural cosmic ray muon,this technology may require long detection time to achieve material identification.The introduction of muon energy in muon tomography is a feasible method to reduce the detection time and was adopted in this thesis.Research on the muon energy measurement based on time of flight method,introducing muon energy into muon tomography and rapid detection of high Z materialwas investigated.Scattering theory of muon tomography was studied,and the theoretical benefit of introducing muon energy to detect high-Z material in muon tomography was deduced.Considering the realization of muon energy measurement,a high-Z material detection method based on energy segment was established.Monte Carlo Simulation of different materials was carried out to demonstrate the performance of this method in the reconstruction of radiation length and material identification.Based on the requirement of muon scattering tomography,the time of flight(TOF)method was proposed for muon energy measurement because of its slight influence on the flux,direction and energy of muon.Energy measurement uncertainty has been investigated and a multilayer TOF method was recommended to enhance the energy measurement accuracy under limited space and time resolution.Correspondingly,a TOF measured energy segment method was established and assessed via the muon event number,detector time resolution and layer amount.Muon energy measure experimental platform was built with two MRPC detectors of 100 ps time resolution.After correction of system delay,both timeand length offlight were acquired,achieving the muon energy measurement and segment.On the basis of Tsinghua muon tomography system,the first muon tomography experimental facility with muon energy measured by time of flight method was built,so that track and time can be reconstructed synchronously for each muon.A Monte Carlo simulation corresponding to this experimental prototype system was established to give theoretical prediction of material identification based on TOF energy segment method.Hypothesis testing and ROC analysis have been adopted to evaluate the performance of high Z material identification before and after the introduction of TOF energy segment.The experimental results have proved that the TOF energy segment performs a 25% promotion in the AUC of high Z material identification than that without muon energy.