【摘要】：X射線成像技術(shù)在醫(yī)療診斷、安全檢查和工業(yè)探傷等領(lǐng)域已經(jīng)有了非常成熟的應(yīng)用�，F(xiàn)在X射線成像技術(shù)向著微焦點和低輻射劑量的方向發(fā)展。傳統(tǒng)的X射線源采用的是燈絲的熱電子發(fā)射,其在電子發(fā)射尺寸、電子發(fā)射溫度以及電子發(fā)射的精確控制方面已經(jīng)不能滿足新一代X射線成像設(shè)備的要求。碳納米管作為一種新型的電子發(fā)射源,其不需要加熱、尺寸加工到很小以及場致發(fā)射的精確可控,使其成為替代熱燈絲作為X射線源的理想材料。傳統(tǒng)的熱燈絲X射線源,由于需要對燈絲進行加熱才能產(chǎn)生熱電子發(fā)射,所以其在發(fā)射過程中一般處于持續(xù)工作模式。然而在X射線線陣掃描成像系統(tǒng)內(nèi),持續(xù)工作的X射線源產(chǎn)生了很多不必要的X射線輻射。利用碳納米管作為陰極制作的冷陰極X射線源,可以通過控制柵極電壓的方式來控制整個射線源處于快速脈沖式工作狀態(tài)。這樣,既可以減少不必要的X射線輻射,又能降低整體射線源能耗,延長X射線管壽命。為了搭建脈沖式工作的冷陰極X射線線掃描系統(tǒng),本文首先研究并設(shè)計并制作了脈沖式工作的冷陰極X射線源,其中包括基于碳納米管場發(fā)射的冷陰極X射線管以及柵極高壓脈沖電源,最后整合成脈沖式冷陰極X射線源,并進行快速脈沖成像測試。利用此冷陰極X射線源,本文設(shè)計并搭建了脈沖式工作模式的冷陰極X射線線掃描成像系統(tǒng)。其中包括同步脈沖工作的X射線線陣探測電路設(shè)計以及脈沖式成像系統(tǒng)的搭建。在完成系統(tǒng)搭建之后,測試了系統(tǒng)的總體輻射劑量和成像效果并與熱燈絲X射線源進行對比,結(jié)果表明基于脈沖式工作模式的冷陰極X射線線掃描系統(tǒng)的輻射劑量比持續(xù)工作的熱燈絲X射線源的輻射劑量降低了70%左右。此結(jié)構(gòu)可以應(yīng)用到現(xiàn)在的X射線安檢設(shè)備當(dāng)中,同時也是經(jīng)過改進可以應(yīng)用到CT系統(tǒng)中,為冷陰極X射線源的應(yīng)用奠定了基礎(chǔ)。
[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.
【學(xué)位授予單位】：東南大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2015
【分類號】：TN14

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