Influence of multiple Coulomb scattering on accuracy of muontransmission imaging of small-scale matter br


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The muon transmission imaging method is a non-destructive detection imaging method and can obtain theinternal density structure of the target object by analyzing the flux change of cosmic ray muon before and afterpassing through the target object. This method assumes that muon travels along a straight line in a lowatomicnumber material. However, the multiple Coulomb scattering causes the muon deviate from the straight line to acertain extent when penetrating the material, which may have a certain influence on the accuracy of muontransmission imaging. This study uses the Geant4 software package to carry out Monte Carlo simulation ofmuon transmission imaging. Object models with multiple density structures and several meters are used toanalyze the effect of multiple scattering on the accuracy of transmission imaging. In the experiment, we set up amodel in which muons of different energy vertically pass through a rock with a certain thickness, we canintuitively see the influence of scattering on the penetration path of muons. By setting up rock-water blockmodels with thickness in a range of 0.8, 2.4 and 4.0 m, the effect of Coulomb scattering on the transmissionimaging of small-scale material muons is analyzed. The results suggest that the muon transmission imagingmethod can well restore the geometric shape and spatial distribution characteristics of density anomalies forobjects with several-meter scale for standard rock materials with a scale of several meters. However, the fluxdeviation caused by multiple Coulomb scattering on the muons in the near-vertical direction can reach 5%, andup to 13% in the boundary areas of the standard rock and air. We limit the scattering angle of the muon, andselect the muon with a scattering angle of less than or equal to 1 degrees for imaging. The results of transmissionimaging by using the selected muon have improved. The image does not have the illusion of an abnormallyincreased flux around the model caused by scattering, but the muon flux in the model area is reduced evenmore, thereby affecting the accuracy of restoring the absolute density of an object using flux differences.Therefore, the effects of multiple Coulomb scattering should be considered for recovering more accurate absolutedensity in small-scale muon transmission imaging study
multiple Coulomb scattering,cosmic ray muons,density structure,imaging accuracy,transmission imaging
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