高能工业CT电子直线加速器焦点测量方法与装置研制  

Focal Spot Measurement Method and Device for High-Energy Industrial CT Electron Linear Accelerator

作　　者：宋文龙 李奉笑 安康[1,2] 周日峰[1,2] Song Wenlong;Li Fengxiao;An Kang;Zhou Rifeng(ICT Research Center,Key Laboratory of Optoelectronic Technology&Systems(Chongqing University),Ministry of Education,Chongqing 400044,China;Industrial CT Non-destructive Testing Engineering Research Center,Ministry of Education,Chongqing University,Chongqing 400044,China)

机构地区：[1]重庆大学光电技术及系统教育部重点实验室ICT研究中心,重庆400044 [2]重庆大学工业CT无损检测教育部工程研究中心,重庆400044

出　　处：《光学学报》2023年第23期333-340,共8页Acta Optica Sinica

基　　金：国家自然科学基金面上项目(12175026);国家自然科学基金重大科研仪器研制项目(11827809)。

摘　　要：电子直线加速器焦点尺寸是影响高能工业CT空间分辨率等关键技术指标的主要因素之一。IEC 62976-2021和GB/T 20129-2015的“三明治”法(或称叠片法)是现行的无损检测用电子直线加速器焦点测试标准。但在实际操作中,该方法不仅过程繁琐,且在胶片曝光、冲洗、条纹计数等过程中人为因素影响大。此外,理论仿真发现“三明治”测试模块的金属片及塑胶片厚度对测量结果影响的误差超过±12.5%。针对该方法的不足,研究并设计了一套焦点测量方法和装置——狭缝平移扫描法及装置,并进行焦点扫描测试和CT空间分辨率验证等实验。结果表明,所提方法相对于“三明治”法,测量结果客观、准确、重复性好,这对于电子直线加速器的焦点尺寸精确测量和高能工业CT系统性能评估和优化设计具有重要意义。Objective Accurately measuring the focal spot size of the electron linear accelerator is important for the optimized design and performance evaluation of high-energy industrial CT systems.However,due to the high energy,high dose rate,and strong penetration ability of X-ray generated by the electron linear accelerator,there are difficulties in accurate measurement of the focal spot size.Currently,the main test standard for the focal spot size of the electron linear accelerator is the"Sandwich"test method proposed in the IEC 62976—2021(or stacking test method in GB/T 20129—2015).However,this method is not only cumbersome in the actual measurement,but also seriously affected by human factors during film exposure,processing,and streak counting.Meanwhile,the thicknesses of the metal and plastic sheets of the"Sandwich"test module have a significant influence on the measurement results of the focal spot size.To this end,we propose a silt translation scanning test method which is more objective,accurate,and better repeatable than the"Sandwich"test method.Methods The limitations of the"Sandwich"test method are analyzed by experiments and simulations.First,two measurements of the focal spot size of the 9 MeV electron linear accelerator are conducted using the"Sandwich"test method with reference to IEC 62976—2021 and GB/T 20129—2015.The differences between the two measurements are compared and the reasons are analyzed.Then we employ the Monte Carlo particle simulation software BEAMnrc to construct the electron linear accelerator and simulate the effect of different metal and plastic sheet thicknesses of the"Sandwich"test module on the focal spot size measurement results.After analyzing the disadvantages of the"Sandwich"test method,the device structure and measurement principle of the slit translation scanning test method are presented.The focal spot size of a 9 MeV electron linear accelerator is measured several times using the slit translation scanning test method for comparison with the"Sandwich"method.Finally,to

关 键 词：X射线光学 高能工业CT 电子直线加速器 焦点尺寸 蒙特卡罗方法 

分 类 号：O434.19[机械工程—光学工程]