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.