基于冷阴极X射线源的脉冲式线扫描系统的研究

发布时间：2019-06-02 06:22

【摘要】：X射线成像技术在医疗诊断、安全检查和工业探伤等领域已经有了非常成熟的应用。现在X射线成像技术向着微焦点和低辐射剂量的方向发展。传统的X射线源采用的是灯丝的热电子发射,其在电子发射尺寸、电子发射温度以及电子发射的精确控制方面已经不能满足新一代X射线成像设备的要求。碳纳米管作为一种新型的电子发射源,其不需要加热、尺寸加工到很小以及场致发射的精确可控,使其成为替代热灯丝作为X射线源的理想材料。传统的热灯丝X射线源,由于需要对灯丝进行加热才能产生热电子发射,所以其在发射过程中一般处于持续工作模式。然而在X射线线阵扫描成像系统内,持续工作的X射线源产生了很多不必要的X射线辐射。利用碳纳米管作为阴极制作的冷阴极X射线源,可以通过控制栅极电压的方式来控制整个射线源处于快速脉冲式工作状态。这样,既可以减少不必要的X射线辐射,又能降低整体射线源能耗,延长X射线管寿命。为了搭建脉冲式工作的冷阴极X射线线扫描系统,本文首先研究并设计并制作了脉冲式工作的冷阴极X射线源,其中包括基于碳纳米管场发射的冷阴极X射线管以及栅极高压脉冲电源,最后整合成脉冲式冷阴极X射线源,并进行快速脉冲成像测试。利用此冷阴极X射线源,本文设计并搭建了脉冲式工作模式的冷阴极X射线线扫描成像系统。其中包括同步脉冲工作的X射线线阵探测电路设计以及脉冲式成像系统的搭建。在完成系统搭建之后,测试了系统的总体辐射剂量和成像效果并与热灯丝X射线源进行对比,结果表明基于脉冲式工作模式的冷阴极X射线线扫描系统的辐射剂量比持续工作的热灯丝X射线源的辐射剂量降低了70%左右。此结构可以应用到现在的X射线安检设备当中,同时也是经过改进可以应用到CT系统中,为冷阴极X射线源的应用奠定了基础。
[Abstract]:X-ray imaging technology has been widely used in medical diagnosis, safety examination and industrial flaw detection. Now X-ray imaging technology is developing in the direction of micro-focus and low radiation dose. The traditional X-ray source adopts the hot electron emission of filament, which can not meet the requirements of the new generation X-ray imaging equipment in the aspects of electron emission size, electron emission temperature and accurate control of electron emission. As a new type of electron emission source, carbon nanotube (CNT) does not need heating, small size processing and accurate control of field emission, which makes it an ideal material to replace hot filament as X-ray source. Because the traditional hot filament X-ray source needs to heat the filament in order to produce hot electron emission, it is generally in continuous working mode in the emission process. However, in the X-ray linear scanning imaging system, the continuous working X-ray source produces a lot of unnecessary X-ray radiation. Using carbon nanotube as the cold cathode X-ray source, the whole ray source can be controlled in a fast pulse state by controlling the gate voltage. In this way, it can not only reduce unnecessary X-ray radiation, but also reduce the energy consumption of the whole ray source and prolong the life of X-ray tube. In order to build a pulse working cold cathode X-ray scanning system, this paper first studies and designs and fabricates the pulse working cold cathode X-ray source. It includes cold cathode X-ray tube based on carbon nanotube field emission and gate high voltage pulse power supply, and finally integrates into pulse cold cathode X-ray source, and carries on the fast pulse imaging test. Using this cold cathode X-ray source, a pulse mode cold cathode X-ray scanning imaging system is designed and built in this paper. It includes the design of X-ray linear array detection circuit and the construction of pulse imaging system. After the construction of the system, the overall radiation dose and imaging effect of the system are tested and compared with the X-ray source of the hot filament. The results show that the radiation dose of the cold cathode X-ray scanning system based on pulse mode is about 70% lower than that of the continuous hot filament X-ray source. This structure can be applied to the current X-ray security inspection equipment, and can also be applied to CT system after improvement, which lays a foundation for the application of cold cathode X-ray source.
【学位授予单位】：东南大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TN14

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