大功率端窗X射线管的束流优化  

Optimization of Electron Beams for End-Window X-Ray Tubes with High Power

作　　者：王思霖 刘俊标[1,2] 王大正 王鹏飞 韩立 Wang Silin;Liu Junbiao;Wang Dazheng;Wang Pengfei;Han Li(Institute of Electrical Engineering,Chinese Academy of Sciences,Beijing 100190,China;University of Chinese Academy of Sciences,Beijing 100049,China)

机构地区：[1]中国科学院电工研究所,北京100190 [2]中国科学院大学,北京100049

出　　处：《光学学报》2023年第22期319-325,共7页Acta Optica Sinica

基　　金：国家重点研发计划(2022YFF0707301)。

摘　　要：目前,国产大功率端窗X射线管存在束流和功率小于设计值的问题。从热电子发射理论和空间电荷受限发射理论出发,对大功率端窗X射线管的束流进行优化研究。在理论仿真中,计算两种理论模型下的电子束轨迹、束流大小和靶面焦斑。计算分析表明,现有问题主要是灯丝附近的电势分布不合理造成的。基于这一分析,对现有结构提出两种优化方案:一种不改变现有结构仅通过改变灯丝电势来克服灯丝附近的空间电荷效应;另一种通过改变灯丝位置来使灯丝附近的加速电压分布更加合理。基于这两种优化方案,再次进行仿真计算,计算结果显示,两种方案可以有效提高现有大功率X射线管的束流。最后设计了验证性实验,测得了该结构在额定最大灯丝电流下的温度限制束流大小,并验证了仿真计算的准确性,同时也验证了提出的两种优化方案的可行性。Objective Wavelength dispersive X-ray fluorescence spectrometer(WDXRF)is widely applied in disparate fields such as metallurgy,building materials,and geological surveys.Its detection principle involves employing a primary X-ray beam to excite a fluorescent beam on the sample,which is then dispersed by a dispersive crystal based on wavelength.The intensities at different wavelengths are measured and a spectrum is generated to qualitatively and quantitatively analyze the elemental composition of the sample.During the test,certain degree of intensity is lost due to the dispersion of X-ray fluorescence by the dispersive crystal.Thus,a higher intensity of the primary X-ray beam is required,which is typically achieved by an X-ray tube with high-power as the excitation source.X-ray tubes with high power can be categorized into two types of side-window and end-window X-ray tubes based on their structural forms.For end-window X-ray tubes,since the window does not absorb backscattered electrons,the beryllium window is relatively thinner,which increases the transmissivity of longer wavelength radiation and facilitates the excitation of light elements.The power of an X-ray tube is determined by the tube voltage and current.Higher tube voltage produces X-rays with higher energy,while larger tube current increases the X-ray brightness.The power of an X-ray tube is influenced by factors such as the distribution of the electric field between the two electrodes inside the tube,cathode material,temperature,surface area,and shape.Currently,Malvern Panalytical is a representative company overseas that produces end-window X-ray tubes with high power,with 75 kV/4 kW being the main specification.In China,end-window X-ray tubes are mainly focused on lowpower applications,and no products are available on the market for end-window X-ray tubes with high power.They are still in the design and testing phase,and there is still a gap in power control and target focal spot control compared with the advanced international level.Therefore,further

关 键 词：X射线源 空间电荷限制 热电子发射 性能优化 

分 类 号：O434[机械工程—光学工程]