聚焦电子束对透射式微焦点X射线源的影响
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摘要
微焦点X射线源是微计算机断层扫描技术设备的核心部件。研究了电子束在靶材中的横向扩散引起的透射式微焦点射线源的焦点尺寸和强度的变化规律。结果表明:当打靶电子束的束流密度遵循高斯分布时,其产生的X射线强度也遵循高斯分布,该分布的标准差可以用来精确表示X射线的焦点尺寸;当靶材厚度可以使沉积电子束的能量达到60%时,对应的靶材产生的X射线强度最高;随着靶材厚度增加,X射线的焦点尺寸逐渐变大;增大电子束的加速电压可以适当减小X射线的焦点。本研究为透射式微焦斑X射线源的靶材选择和设计提供了理论依据。
Microfocus X-ray source is the core component of micro-computed tomography(micro-CT). This study investigates the relationship between the changes in the focal spot size and intensity of the transmission microfocus X-ray source caused by the lateral diffusion of the electron beam in the target. Results show that, if the density distribution of the electron beam follows a Gaussian distribution, the distribution of the X-ray intensity should also be Gaussian. The standard deviation of the X-ray intensity distribution exactly represents the size of the X-ray focal spot. Furthermore, results show that when the energy deposition of the electron beam in the target reaches 60%, the intensity of the X-ray produced by the target reaches the maximum value, correspondingly. With an increase in the target thickness, the focal spot size of the X-ray source gradually increases; conversely, an increase in the acceleration voltage of the electron beam can appropriately reduce the focal spot size of the X-ray source. This study provides theoretical guidance for target material selection and design of transmission microfocus X-ray source.
Microfocus X-ray source is the core component of micro-computed tomography(micro-CT). This study investigates the relationship between the changes in the focal spot size and intensity of the transmission microfocus X-ray source caused by the lateral diffusion of the electron beam in the target. Results show that, if the density distribution of the electron beam follows a Gaussian distribution, the distribution of the X-ray intensity should also be Gaussian. The standard deviation of the X-ray intensity distribution exactly represents the size of the X-ray focal spot. Furthermore, results show that when the energy deposition of the electron beam in the target reaches 60%, the intensity of the X-ray produced by the target reaches the maximum value, correspondingly. With an increase in the target thickness, the focal spot size of the X-ray source gradually increases; conversely, an increase in the acceleration voltage of the electron beam can appropriately reduce the focal spot size of the X-ray source. This study provides theoretical guidance for target material selection and design of transmission microfocus X-ray source.
引文
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[2] Gui J B,Hu Z L,Zhou Y,et al.Technology development of micro-CT with high spatial resolution[J].Computerized Tomography Theory and Applications,2009,18(2):106-116.桂建保,胡战利,周颖,等.高分辨显微CT技术进展[J].CT理论与应用研究,2009,18(2):106-116.
[3] Yan J,Jiang S E,Su M,et al.The application of phase contrast imaging to ICF multi-shell capsule diagnosis[J].Acta Physica Sinica,2012,61(6):068703.晏骥,江少恩,苏明,等.X射线相衬成像应用于惯性约束核聚变多层球壳靶丸检测[J].物理学报,2012,61(6):068703.
[4] Liu J B,Xi X Q,Han Y,et al.A new scattering artifact correction method based on K-N formula for cone-beam computed tomography[J].Acta Optica Sinica,2018,38(11):1134001.刘建邦,席晓琦,韩玉,等.基于K-N模型的锥束CT散射伪影校正方法[J].光学学报,2018,38(11):1134001.
[5] Wang K G,Niu H B,Li J,et al.A new protable X-ray source with micro-beam[J].Acta Photonica Sinica,2004,33(6):672-676.王凯歌,牛憨笨,李冀,等.一种新型微束斑X射线源的研究[J].光子学报,2004,33(6):672-676.
[6] Ihsan A,Heo S H,Cho S O.Optimization of X-ray target parameters for a high-brightness microfocus X-ray tube[J].Nuclear Instruments and Methods in Physics Research Section B:Beam Interactions with Materials and Atoms,2007,264(2):371-377.
[7] Li B L,Zhang P Y,Li B,et al.Optimized iterative method for projection decomposition of X-ray dual-energy computed tomography[J].Acta Optica Sinica,2017,37(10):1034001.李保磊,张萍宇,李斌,等.X射线双能计算机层析成像投影分解的优化迭代方法[J].光学学报,2017,37(10):1034001.
[8] Li Y G,Zhou W H,Huang L F,et al.Theoretical simulation of thermal behavior in transient heat loads testing of plasma-facing materials[J].Fusion Engineering and Design,2011,86(12):2812-2820.
[9] Trincavelli J,Castellano G.The prediction of thick target electron bremsstrahlung spectra in the 0.25-50 keV energy range[J].Spectrochimica Acta Part B:Atomic Spectroscopy,2008,63(1):1-8.
[10] Zheng L,Liu H R,Sun B L,et al.Optimization of transmission-type anode target in microfocus X-ray tube[J].Chinese Journal of Vacuum Science and Technology,2015,35(12):1443-1448.郑磊,刘华荣,孙步梁,等.微焦点X射线管透射式阳极靶的优化设计[J].真空科学与技术学报,2015,35(12):1443-1448.
[11] Ma Y T,Liu J B,Huo R L,et al.Research on the preparation and performance of tungsten-aluminum transmission target for micro-computed tomography by magnetron sputtering[J].Acta Metallurgica Sinica,2015,51(11):1416-1424.马玉田,刘俊标,霍荣岭,等.基于磁控溅射法显微CTW-Al透射靶材的制备及其性能研究[J].金属学报,2015,51(11):1416-1424.
[12] Ihsan A,Heo S H,Cho S O.A microfocus X-ray tube based on a microstructured X-ray target[J].Nuclear Instruments and Methods in Physics Research Section B:Beam Interactions with Materials and Atoms,2009,267(21/22):3566-3573.
[13] Hyun J K,Ercius P,Muller D A.Beam spreading and spatial resolution in thick organic specimens[J].Ultramicroscopy,2008,109(1):1-7.
[14] Xu X D,Zhou B,Guo J C,et al.Monte Carlo simulation of interaction of electrons with anode in microstructure X-ray tubes[J].Chinese Journal of Computational Physics,2018,35(1):95-102.徐小东,周彬,郭金川,等.微结构X射线源中电子与阳极作用的蒙特卡罗模拟[J].计算物理,2018,35(1):95-102.
[15] Zhang X,Robinson V S,Raber T R,et al.THERMAL analysis of high-power X-ray target:scaling effects[J].Proceedings of SPIE,2015,9590:95900G.
[16] Saeed Raza H,Jin Kim H,Nam Kim H,et al.Angle dependent focal spot size of a conical X-ray target[J].Applied Radiation and Isotopes,2015,96:6-12.
[17] Hu J W,Lü W,An B,et al.Review on simulation methods of micro focal spot X-ray tubes′ electron emission system[C]//2014 15th International Conference on Electronic Packaging Technology,August 12-15,2014,Chengdu,China.New York:IEEE,2014:1502-1506.
[18] Salamon M,Hanke R,Krüger P,et al.Comparison of different methods for determining the size of a focal spot of microfocus X-ray tubes[J].Nuclear Instruments and Methods in Physics Research Section A:Accelerators,Spectrometers,Detectors and Associated Equipment,2008,591(1):54-58.
[19] Korenev S.Target for production of X-rays[C]//Proceedings of the 2003 Particle Accelerator Conference,May 12-16,2003,Portland,OR,USA.New York:IEEE,2003:1614-1615.