工业CT已经成为机械、航空、国防、冶金等众多领域中不可或缺的无损检测技术。 60Co同位素具有能量单一、输出稳定等众多优势，将其用于工业CT做射线源，能大大减小射线硬化等不利因素，非常有利于成像。清华大学核研院提出了以60Co为射线源、基于平板探测器和固体线阵探测器双结构的高精度工业CT系统的研究课题。本论文依托该课题，以60Co工业CT系统为研究对象，对系统性能评估、参数优化及系统调校及参数获取等方面进行研究。与X光机和加速器相比，60Co作为射线源有许多优势，同时也有一些不足之处，论文对此进行全面的比较分析。之后介绍了60Co工业CT研究平台各部分组成，并进行了初步的实验研究，分析了研究平台存在的主要问题。研究60Co工业CT系统对缺陷检测能力的估算方法是系统优化设计的重要指导工具。论文结合工业CT密度分辨率的标准估算公式，以缺陷中最具代表性的裂纹为检测对象，推导出了一种工业CT对裂纹检测能力的估算方法。利用该估算方法对公式中涉及到的系统参数进行了全面分析。仿真技术是有力的研究手段。为此论文开发了60Co工业CT仿真平台。针对60Co焦点比较大的问题，采用离散化的方法进行全面、深入的仿真分析，得出不同方向尺寸对成像有不同的影响。之后对一系列参数对成像的影响进行仿真分析，对各参数的取值分别提出了有针对性的建议。系统参数的优化设计能使系统获得更好的检测能力，而检测能力的实现则依赖于系统的正确调校和参数的准确获取。论文研究了一种基于正交金属丝的系统调校和参数获取方法，仅需要少量投影即可实现。该方法合理安排调校顺序，最大限度的避免了不同偏差对投影作用的相互叠加。经误差分析，得到的几何参数误差很小，满足使用。论文最后将这些优化结果和方法应用于60Co工业CT研究平台，并进行了一系列的实验研究。采用平板探测器和线阵探测器对特制套筒进行CT扫描实验，确定系统的裂纹检测能力，结果与理论估算和仿真实验相互验证。此外，利用平板探测器对大量检测客体进行锥束CT扫描实验，得到了比较好的重建图像。
Industrial CT has become a indispensable detective tool in social production, social life and national defense weaponry industry. As opposed to X-ray source, 60Co isotope has many advantages such as single energy and output stability, As industrial CT-ray source, it can greatly reduce the negative factors such as beam hardening, and it is very conducive to imaging. INET, Tsinghua University proposed to take 60Co as radiation source, flat-panel detector and linear array detector as detectors to build a double-precision industrial CT system. Relying on the subject, this paper researches 60Co industrial CT system on system performance evaluation, optimization, system calibration and parameters obtaining.Compared to X-ray and accelerator, 60Co has many advantages, but also has some shortcomings as radiation source, this paper carried out a comprehensive comparative analysis. Various parts of the 60Co industrial CT research platform were introduced. The main problems of the research platform were analyzed.The estimation method of 60Co industrial CT system defect detection capability is an important guidance system optimization tool. The Paper derived a crack detection capability of industrial CT estimation methods with industry standard resolution CT density estimation formula, taking cracks as the most representative defects. System parameters in the formula were analyzed comprehensively.Simulation technology is a powerful research tool. The paper has developed a simulation platform. Focus for the 60Co bigger issue, the paper conducted a comprehensive, in-depth simulation analysis. The sizes of the focus in different directions have different effects. After a series analysis of parameters to simulate the impact of imaging, the values of each parameter were made targeted recommendations.Optimization of system parameters makes the system have better detection capabilities, and detection system is dependent on the realization of obtaining an accurate calibration and parameters rightly. Thesis of a system based on orthogonal wire calibration and parameter acquisition method requires only a small amount of projection can be realized. This method is reasonable arrangements calibration sequence, the maximum deviation by the effect of different superposition of the projection was avoid. After analysis, the geometric parameter error is smallenough to be used.Finally, the results of the optimization method were applied to 60Co industrial CT research platform, and a series of experiments were conducted. The flat-panel detector and linear array detector were used to CT scan a special sleeve for experiments to determine the system's ability to crack detection. The results were authenticated with theoretical estimates and simulation. In addition, the flat-panel detector was used for detecting a large number of cone-beam CT scan objects for experiments, and good image were reconstructed.
