工业X-CT用闪烁晶体性能的MCNP

东华理工大学毕业设计(论文) 摘要

摘要

工业X-CT虽在原理上与医学X-CT相类似，但在系统结构设计和对X射线探测及扫描方式等方面二者却存在极大的差异，其系统结构设计将因被检测对象的不同而进行个性化的设计，因而对闪烁晶体的尺寸难于做到统一的标准尺寸，且晶体中还掺入了对人体有剧毒的杂质Tl和Cd等元素，这样对系统结构设计及人为操作方面带来困难。基此，针对工业X-CT系统中如何实现对X射线的高效探测问题，本论文采用蒙特卡罗方法，模拟研究了CsI(T1)、NaI(T1)、CdWO4 闪烁晶体与X射线作用后，其在能量分布、全能峰效率及闪烁体转换效率方面的性能。研究结果发现，CsI（Tl）闪烁晶体在全能峰效率，闪烁体转换效率，光特性及易于加工等方面，综合性能最优，它可以作为工业X-CT系统中对X射线高效探测的理想选择，当CsI(T1)晶体长度为1.5cm时，X射线能量为220keV时，探测器的全能峰效率高达62.3%，转换效率高达74.3%。这一结果可以给X-CT系统结构设计及操作方面带来重大参考价值。

关键词：工业X-CT；闪烁晶体；MCNP

ABSTRACT

Industrial X-CT is similar with the medical X-CT in principle, but there are great differences between system architecture design and X-ray detection and scanning,besides,the system design will be designed personalizely due to different detected object, and thus the size of s cintillation crystals can’t achieve a uniform standard , and the crystal mixed with impurities such as Tl and Cd elements are also highly toxic to humans.Thus,it brings difficult to system architecture design and man-caused operational. Based on this, this paper takes Monte Carlo method for how to achieve efficient detection of X-ray problem in industrial X-CT system,and simulate energy distribution, the peak efficiency all-round performance of CsI (Tl), NaI (T1), CdWO4scintillation crysta after they acted with the role of X-ray.The results showed that, CsI (T1) scintillation crystal has optical properties in the all-round peak efficiency, scintillator conversion efficiency, and easy processing, etc. It can be used as ideal for X-ray high efficiency probe in industrial X-CT system. when the crystal length is1.5cm,and X-ray energy 220keV, the detector efficiency reached as high as 62.3% and all-round peak conversion efficiency as high as 74.3%. This result can bring great reference value of X-CT system design and operation of significant aspects.

Key words: Industrial X-CT; scintillation crystal; MCNP

目录

绪论 (1)

1 工业X-CT (2)

1.1 射线与物质的相互作用 (2)

1.1.1 光电效应 (2)

1.1.2 康普顿效应 (3)

1.1.3 电子对效应 (3)

1.2 工业X-CT的结构和原理 (3)

1.2.1工业X-CT基本原理 (4)

1.2.2工业X-CT的结构工作原理 (5)

1.3工业X-CT的新发展 (6)

2 闪烁晶体的性能 (7)

2.1 闪烁晶体的种类 (7)

2.2 闪烁晶体的物理特性 (7)

2.2.1 物理性能 (8)

2.2.2 全能峰效率 (8)

2.2.3 转换效率 (8)

3 蒙特卡罗方法与MCNP程序 (9)

3.1 蒙特卡罗方法模拟原理 (9)

3.2 蒙特卡罗方法的解题步骤 (10)

3.3 基于蒙特卡罗方法的MCNP程序 (11)

3.3.1 MCNP程序的发展 (11)

3.3.2 MCNP程序的特点 (12)

3.3.3 MCNP的应用状况 (13)

4 MCNP模型的建立与程序模拟 (15)

4.1 MCNP模拟的空间布置 (15)

4.2闪烁晶体性能MCNP模拟 (16)

4.2.1能量分布的MCNP模拟 (16)

4.2.2全能峰效率的MCNP模拟 (16)

4.2.3闪烁体转换效率的MCNP模拟 (19)

结论 (22)

致谢 (23)

参考文献 (24)

附录1 (25)

附录2 (26)

附录3 (27)