Optimum Design Of γ-CT System Based On Geant4 Simulation For Multiphase Flow Measurement

Multi-phase flow widely exists in industrial process, such as oil, chemical engineering,power industry etc. It is important to obtain the parameters of multi-phase flow. Owning to the advantages of non-invasiveness, visualization and high-precision, computed tomography technique is widely applied to clinical monitoring and multiphase flow measurement. This dissertation investigates the Design and experiments ofγ-CT System for Multiphase flow measurement.This dissertation investigates the basic theory of multi-phase flow detection technology and CT system, simulates CT system using Geant4 software and compares several image reconstruction algorithms. A system scheme of theγ-ray CT system for Multi-phase flow is constructed and practical experiment is conducted,that result are analyzed and compared with simulation .(1)System Modeling and Simulation.This thesis established simulation model of multi-phases CT system using Geant4 software, simulated the physical process of the multi-phases CT system and obtained simulation data. The author investigates the steps of modeling, According to Scattering Photon rate,Image Correlation coefficient and Relative Image error, the optimum design of collimator, the number of radiation sources and the number of detectors were performed. Combined with the actual construction of industrial pipe size, diameter of 50mm, 80mm, 100mm pipeline 5 sourceγ-CT system are constructed respectively .(2)Image Reconstruction AlgorithmSeveral image reconstruction algorithms have been investigated, such as linear back projection method, ART、CG and Landweber iteration method etc. The cross section of the image is reconstructed using these algorithms and simulation data acquired from Geant4. The performance of the reconstruction algorithms are compared with each other.(3)Experiments ofγ-ray CT SystemA system scheme of theγ-ray CT system for Multi-phase flow is constructed ,which comprises one 300mCi 241Am source and 17 CdZnTe detector units. Several experiments are conducted , whose result are analyzed and compared with simulation . A particular system analysis is provided in the following section about basic factors which affect the image quality of theγ-ray CT scanner. Both simulation and experimental results show that our CT system can reconstruct satisfactory cross- sectional images from limited projections.Finally, according to existing problems in multiphase flowγ-CT system , some improvement suggestions are presented and discussed also.